[PATCH V3 00/11] PCI passthru on Hyper-V (Part I)

[PATCH V3 00/11] PCI passthru on Hyper-V (Part I)

[Mukesh R]

Implement passthru of PCI devices to unprivileged virtual machines
(VMs) when Linux is running as a privileged VM on Microsoft Hyper-V
hypervisor. This support is made to fit within the workings of VFIO
framework, and any VMM needing to use it must use the VFIO subsystem.
This supports both full device passthru and SR-IOV based VFs.

At a high level, the hypervisor supports traditional mapped iommu domains
that use explicit map and unmap hypercalls for mapping and unmapping guest
RAM into the iommu subsystem. Hyper-V also has a concept of direct attach
devices whereby the iommu subsystem simply uses the guest HW page table
(ept/npt/..). This series adds support for both, and both are made to
work with the VFIO subsystem.

While this Part I focuses on memory mappings, Part II focuses on irq 
remapping and irq migrations.

This series rebased to: 5170a82e8921 (origin/hyperv-next)

Testing:
 o Most testing done on hyperv-next:e733a9e28180 using Cloud Hypervisor (51).
 o Limited testing on : 5170a82e8921
 o Tested with impending Part II irq patches.
 o All tests involved passthru of devices using MSIx.
 o Following combinations were tested doing PF passthru:
    - L1VH(1): test 1: Mellanox ConnectX-6 Lx passthru
               test 2: NVIDIA Tesla Tesla T4 GPU.
               test 3: Both of above simultaneous passthru
    - Baremetal dom0/root: All of above.
 o VF: Mellanox ConnectX-6 Lx passthru on baremetal dom0/root.

(1) L1VH: this is a semi privileged VM that runs on Windows root on
          Hyper-V, and allows users to create more child VMs.

This series strives to establish a base line. Some pending work items:
 o arm64 : some delta to make this work on arm64 (in progress).
 o Qemu and OpenVMM support (in progress).
 o Further VF testing on l1vh
 o device sleep/wakeup.
 o More stress testing with high end GPUs

Changes in V3:
 o patch #8: fix compiler issues incase of !CONFIG_HYPERV. Also, do forward
   declaration of struct pci_dev instead of including pci.h.
 o patch #9: minor changes to comments. Pass hv_domain instead of 
   iommu_domain to hv_iommu_detach_dev() since that's what it needs. Set
   device private to null if attach fails. Clam down number of PFNs passed
   to hv_iommu_map_pgs().

Changes in V2:
 o rebase to 5170a82e8921
 o minor fixes for arm64 build
 o drop patch 03: "x86/hyperv: add insufficient memory support in irqdomain.c" 
     as it that path is no longer used
 o drop patch 08: "PCI: hv: rename hv_compose_msi_msg .. " and do it separately
   outside this series.
 o minor updates to commit messages

Changes in V1:
 o patch 1: Don't tie hyperv-irq.c to CONFIG_HYPERV_IOMMU.
 o patch 4: Redesigned to address security vulnerability found by copilot 
            with passing tgid as a parameter.  Also, do tgid setting right 
            after setting pt_id.
 o patch 5: Remove unused type parameter from mshv_device_ops.device_create
 o patch 7: mshv_partition_ioctl_create_device cleanup on copy_to_user.
 o patch 10: Add export of hv_build_devid_type_pci here to get rid of 
             patch 11.
 o patch 12: Move functions to build device ids from patch 11 here for
             the benefit of arm64. Rename file to: hyperv-iommu-root.c.
 o patch 13: removed to be made part of interrupt part II of this support.
 o patch 14: get rid of fast path to reduce review noise.
 o New (last) patch to pin ram regions if device passthru to a VM.

Thanks,
-Mukesh

Mukesh R (11):
  iommu/hyperv: Rename hyperv-iommu.c to hyperv-irq.c
  x86/hyperv: Cosmetic changes in irqdomain.c for readability
  mshv: Provide a way to get partition ID if running in a VMM process
  mshv: Declarations and definitions for VFIO-MSHV bridge device
  mshv: Implement mshv bridge device for VFIO
  mshv: Add ioctl support for MSHV-VFIO bridge device
  mshv: Import data structs around device passthru from hyperv headers
  PCI: hv: VMBus and PCI device IDs for PCI passthru
  x86/hyperv: Implement Hyper-V virtual IOMMU
  mshv: Populate mmio mappings for PCI passthru
  mshv: Mark mem regions as non-movable upfront if device passthru

 MAINTAINERS                                   |   3 +-
 arch/x86/hyperv/irqdomain.c                   | 199 ++--
 arch/x86/include/asm/mshyperv.h               |   6 +
 arch/x86/kernel/pci-dma.c                     |   2 +
 drivers/hv/Makefile                           |   3 +-
 drivers/hv/mshv_root.h                        |  21 +
 drivers/hv/mshv_root_main.c                   | 266 ++++-
 drivers/hv/mshv_vfio.c                        | 211 ++++
 drivers/iommu/Kconfig                         |   5 +-
 drivers/iommu/Makefile                        |   3 +-
 drivers/iommu/hyperv-iommu-root.c             | 918 ++++++++++++++++++
 .../iommu/{hyperv-iommu.c => hyperv-irq.c}    |   6 +-
 drivers/iommu/irq_remapping.c                 |   2 +-
 drivers/pci/controller/pci-hyperv.c           |  24 +
 include/asm-generic/mshyperv.h                |  33 +
 include/hyperv/hvgdk_mini.h                   |  11 +
 include/hyperv/hvhdk_mini.h                   | 112 +++
 include/linux/hyperv.h                        |   6 +
 include/uapi/linux/mshv.h                     |  31 +
 19 files changed, 1740 insertions(+), 122 deletions(-)
 create mode 100644 drivers/hv/mshv_vfio.c
 create mode 100644 drivers/iommu/hyperv-iommu-root.c
 rename drivers/iommu/{hyperv-iommu.c => hyperv-irq.c} (99%)

-- 
2.51.2.vfs.0.1

[PATCH V3 01/11] iommu/hyperv: Rename hyperv-iommu.c to hyperv-irq.c

[Mukesh R]

This file actually implements irq remapping, so rename to more appropriate
hyperv-irq.c. A new file to implement hyperv iommu will be introduced
later.  Also, it should not be tied to HYPERV_IOMMU, but to CONFIG_HYPERV
and IRQ_REMAP. The file already has #ifdef CONFIG_IRQ_REMAP.

Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
---
 MAINTAINERS                                    | 2 +-
 drivers/iommu/Makefile                         | 2 +-
 drivers/iommu/{hyperv-iommu.c => hyperv-irq.c} | 6 +++---
 drivers/iommu/irq_remapping.c                  | 2 +-
 4 files changed, 6 insertions(+), 6 deletions(-)
 rename drivers/iommu/{hyperv-iommu.c => hyperv-irq.c} (99%)

diff --git a/MAINTAINERS b/MAINTAINERS
index d1cc0e12fe1f..f803a6a38fee 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11914,7 +11914,7 @@ F:	drivers/clocksource/hyperv_timer.c
 F:	drivers/hid/hid-hyperv.c
 F:	drivers/hv/
 F:	drivers/input/serio/hyperv-keyboard.c
-F:	drivers/iommu/hyperv-iommu.c
+F:	drivers/iommu/hyperv-irq.c
 F:	drivers/net/ethernet/microsoft/
 F:	drivers/net/hyperv/
 F:	drivers/pci/controller/pci-hyperv-intf.c
diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
index 0275821f4ef9..335ea77cced6 100644
--- a/drivers/iommu/Makefile
+++ b/drivers/iommu/Makefile
@@ -30,7 +30,7 @@ obj-$(CONFIG_TEGRA_IOMMU_SMMU) += tegra-smmu.o
 obj-$(CONFIG_EXYNOS_IOMMU) += exynos-iommu.o
 obj-$(CONFIG_FSL_PAMU) += fsl_pamu.o fsl_pamu_domain.o
 obj-$(CONFIG_S390_IOMMU) += s390-iommu.o
-obj-$(CONFIG_HYPERV_IOMMU) += hyperv-iommu.o
+obj-$(CONFIG_HYPERV) += hyperv-irq.o
 obj-$(CONFIG_VIRTIO_IOMMU) += virtio-iommu.o
 obj-$(CONFIG_IOMMU_SVA) += iommu-sva.o
 obj-$(CONFIG_IOMMU_IOPF) += io-pgfault.o
diff --git a/drivers/iommu/hyperv-iommu.c b/drivers/iommu/hyperv-irq.c
similarity index 99%
rename from drivers/iommu/hyperv-iommu.c
rename to drivers/iommu/hyperv-irq.c
index 479103261ae6..d11076f906fb 100644
--- a/drivers/iommu/hyperv-iommu.c
+++ b/drivers/iommu/hyperv-irq.c
@@ -8,6 +8,8 @@
  * Author : Lan Tianyu <Tianyu.Lan@microsoft.com>
  */
 
+#ifdef CONFIG_IRQ_REMAP
+
 #include <linux/types.h>
 #include <linux/interrupt.h>
 #include <linux/irq.h>
@@ -24,8 +26,6 @@
 
 #include "irq_remapping.h"
 
-#ifdef CONFIG_IRQ_REMAP
-
 /*
  * According 82093AA IO-APIC spec , IO APIC has a 24-entry Interrupt
  * Redirection Table. Hyper-V exposes one single IO-APIC and so define
@@ -331,4 +331,4 @@ static const struct irq_domain_ops hyperv_root_ir_domain_ops = {
 	.free = hyperv_root_irq_remapping_free,
 };
 
-#endif
+#endif  /* CONFIG_IRQ_REMAP */
diff --git a/drivers/iommu/irq_remapping.c b/drivers/iommu/irq_remapping.c
index c2443659812a..41bf65e4ea88 100644
--- a/drivers/iommu/irq_remapping.c
+++ b/drivers/iommu/irq_remapping.c
@@ -108,7 +108,7 @@ int __init irq_remapping_prepare(void)
 	else if (IS_ENABLED(CONFIG_AMD_IOMMU) &&
 		 amd_iommu_irq_ops.prepare() == 0)
 		remap_ops = &amd_iommu_irq_ops;
-	else if (IS_ENABLED(CONFIG_HYPERV_IOMMU) &&
+	else if (IS_ENABLED(CONFIG_HYPERV) &&
 		 hyperv_irq_remap_ops.prepare() == 0)
 		remap_ops = &hyperv_irq_remap_ops;
 	else
-- 
2.51.2.vfs.0.1

Re: [PATCH V3 01/11] iommu/hyperv: Rename hyperv-iommu.c to hyperv-irq.c

[Souradeep Chakrabarti]

On Mon, May 11, 2026 at 07:02:49PM -0700, Mukesh R wrote:
> This file actually implements irq remapping, so rename to more appropriate
> hyperv-irq.c. A new file to implement hyperv iommu will be introduced
> later.  Also, it should not be tied to HYPERV_IOMMU, but to CONFIG_HYPERV
> and IRQ_REMAP. The file already has #ifdef CONFIG_IRQ_REMAP.
> 
> Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
Reviewed-by: Souradeep Chakrabarti <schakrabarti@linux.microsoft.com>
> Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
> ---
>  MAINTAINERS                                    | 2 +-
>  drivers/iommu/Makefile                         | 2 +-
>  drivers/iommu/{hyperv-iommu.c => hyperv-irq.c} | 6 +++---
>  drivers/iommu/irq_remapping.c                  | 2 +-
>  4 files changed, 6 insertions(+), 6 deletions(-)
>  rename drivers/iommu/{hyperv-iommu.c => hyperv-irq.c} (99%)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index d1cc0e12fe1f..f803a6a38fee 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -11914,7 +11914,7 @@ F:	drivers/clocksource/hyperv_timer.c
>  F:	drivers/hid/hid-hyperv.c
>  F:	drivers/hv/
>  F:	drivers/input/serio/hyperv-keyboard.c
> -F:	drivers/iommu/hyperv-iommu.c
> +F:	drivers/iommu/hyperv-irq.c
>  F:	drivers/net/ethernet/microsoft/
>  F:	drivers/net/hyperv/
>  F:	drivers/pci/controller/pci-hyperv-intf.c
> diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
> index 0275821f4ef9..335ea77cced6 100644
> --- a/drivers/iommu/Makefile
> +++ b/drivers/iommu/Makefile
> @@ -30,7 +30,7 @@ obj-$(CONFIG_TEGRA_IOMMU_SMMU) += tegra-smmu.o
>  obj-$(CONFIG_EXYNOS_IOMMU) += exynos-iommu.o
>  obj-$(CONFIG_FSL_PAMU) += fsl_pamu.o fsl_pamu_domain.o
>  obj-$(CONFIG_S390_IOMMU) += s390-iommu.o
> -obj-$(CONFIG_HYPERV_IOMMU) += hyperv-iommu.o
> +obj-$(CONFIG_HYPERV) += hyperv-irq.o
>  obj-$(CONFIG_VIRTIO_IOMMU) += virtio-iommu.o
>  obj-$(CONFIG_IOMMU_SVA) += iommu-sva.o
>  obj-$(CONFIG_IOMMU_IOPF) += io-pgfault.o
> diff --git a/drivers/iommu/hyperv-iommu.c b/drivers/iommu/hyperv-irq.c
> similarity index 99%
> rename from drivers/iommu/hyperv-iommu.c
> rename to drivers/iommu/hyperv-irq.c
> index 479103261ae6..d11076f906fb 100644
> --- a/drivers/iommu/hyperv-iommu.c
> +++ b/drivers/iommu/hyperv-irq.c
> @@ -8,6 +8,8 @@
>   * Author : Lan Tianyu <Tianyu.Lan@microsoft.com>
>   */
>  
> +#ifdef CONFIG_IRQ_REMAP
> +
>  #include <linux/types.h>
>  #include <linux/interrupt.h>
>  #include <linux/irq.h>
> @@ -24,8 +26,6 @@
>  
>  #include "irq_remapping.h"
>  
> -#ifdef CONFIG_IRQ_REMAP
> -
>  /*
>   * According 82093AA IO-APIC spec , IO APIC has a 24-entry Interrupt
>   * Redirection Table. Hyper-V exposes one single IO-APIC and so define
> @@ -331,4 +331,4 @@ static const struct irq_domain_ops hyperv_root_ir_domain_ops = {
>  	.free = hyperv_root_irq_remapping_free,
>  };
>  
> -#endif
> +#endif  /* CONFIG_IRQ_REMAP */
> diff --git a/drivers/iommu/irq_remapping.c b/drivers/iommu/irq_remapping.c
> index c2443659812a..41bf65e4ea88 100644
> --- a/drivers/iommu/irq_remapping.c
> +++ b/drivers/iommu/irq_remapping.c
> @@ -108,7 +108,7 @@ int __init irq_remapping_prepare(void)
>  	else if (IS_ENABLED(CONFIG_AMD_IOMMU) &&
>  		 amd_iommu_irq_ops.prepare() == 0)
>  		remap_ops = &amd_iommu_irq_ops;
> -	else if (IS_ENABLED(CONFIG_HYPERV_IOMMU) &&
> +	else if (IS_ENABLED(CONFIG_HYPERV) &&
>  		 hyperv_irq_remap_ops.prepare() == 0)
>  		remap_ops = &hyperv_irq_remap_ops;
>  	else
> -- 
> 2.51.2.vfs.0.1
> 

Re: [PATCH V3 01/11] iommu/hyperv: Rename hyperv-iommu.c to hyperv-irq.c

[Jacob Pan]

Hi Mukesh,

On Mon, 11 May 2026 19:02:49 -0700
Mukesh R <mrathor@linux.microsoft.com> wrote:

> This file actually implements irq remapping, so rename to more
> appropriate hyperv-irq.c. A new file to implement hyperv iommu will
> be introduced later.  Also, it should not be tied to HYPERV_IOMMU,
> but to CONFIG_HYPERV and IRQ_REMAP. The file already has #ifdef
> CONFIG_IRQ_REMAP.
> 
> Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
> Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
> ---
>  MAINTAINERS                                    | 2 +-
>  drivers/iommu/Makefile                         | 2 +-
>  drivers/iommu/{hyperv-iommu.c => hyperv-irq.c} | 6 +++---
Given that we have multiple Hyper-V IOMMU-related files — this renamed
hyperv-irq.c, the existing hyperv-iommu code, iommu-root (this
series) and the recently posted guest pvIOMMU driver — should we create
a drivers/iommu/hyperv/ directory to consolidate them?

>  drivers/iommu/irq_remapping.c                  | 2 +-
>  4 files changed, 6 insertions(+), 6 deletions(-)
>  rename drivers/iommu/{hyperv-iommu.c => hyperv-irq.c} (99%)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index d1cc0e12fe1f..f803a6a38fee 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -11914,7 +11914,7 @@ F:	drivers/clocksource/hyperv_timer.c
>  F:	drivers/hid/hid-hyperv.c
>  F:	drivers/hv/
>  F:	drivers/input/serio/hyperv-keyboard.c
> -F:	drivers/iommu/hyperv-iommu.c
> +F:	drivers/iommu/hyperv-irq.c
>  F:	drivers/net/ethernet/microsoft/
>  F:	drivers/net/hyperv/
>  F:	drivers/pci/controller/pci-hyperv-intf.c
> diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
> index 0275821f4ef9..335ea77cced6 100644
> --- a/drivers/iommu/Makefile
> +++ b/drivers/iommu/Makefile
> @@ -30,7 +30,7 @@ obj-$(CONFIG_TEGRA_IOMMU_SMMU) += tegra-smmu.o
>  obj-$(CONFIG_EXYNOS_IOMMU) += exynos-iommu.o
>  obj-$(CONFIG_FSL_PAMU) += fsl_pamu.o fsl_pamu_domain.o
>  obj-$(CONFIG_S390_IOMMU) += s390-iommu.o
> -obj-$(CONFIG_HYPERV_IOMMU) += hyperv-iommu.o
> +obj-$(CONFIG_HYPERV) += hyperv-irq.o
>  obj-$(CONFIG_VIRTIO_IOMMU) += virtio-iommu.o
>  obj-$(CONFIG_IOMMU_SVA) += iommu-sva.o
>  obj-$(CONFIG_IOMMU_IOPF) += io-pgfault.o
> diff --git a/drivers/iommu/hyperv-iommu.c b/drivers/iommu/hyperv-irq.c
> similarity index 99%
> rename from drivers/iommu/hyperv-iommu.c
> rename to drivers/iommu/hyperv-irq.c
> index 479103261ae6..d11076f906fb 100644
> --- a/drivers/iommu/hyperv-iommu.c
> +++ b/drivers/iommu/hyperv-irq.c
> @@ -8,6 +8,8 @@
>   * Author : Lan Tianyu <Tianyu.Lan@microsoft.com>
>   */
>  
> +#ifdef CONFIG_IRQ_REMAP
> +
>  #include <linux/types.h>
>  #include <linux/interrupt.h>
>  #include <linux/irq.h>
> @@ -24,8 +26,6 @@
>  
>  #include "irq_remapping.h"
>  
> -#ifdef CONFIG_IRQ_REMAP
> -
>  /*
>   * According 82093AA IO-APIC spec , IO APIC has a 24-entry Interrupt
>   * Redirection Table. Hyper-V exposes one single IO-APIC and so
> define @@ -331,4 +331,4 @@ static const struct irq_domain_ops
> hyperv_root_ir_domain_ops = { .free = hyperv_root_irq_remapping_free,
>  };
>  
> -#endif
> +#endif  /* CONFIG_IRQ_REMAP */
> diff --git a/drivers/iommu/irq_remapping.c
> b/drivers/iommu/irq_remapping.c index c2443659812a..41bf65e4ea88
> 100644 --- a/drivers/iommu/irq_remapping.c
> +++ b/drivers/iommu/irq_remapping.c
> @@ -108,7 +108,7 @@ int __init irq_remapping_prepare(void)
>  	else if (IS_ENABLED(CONFIG_AMD_IOMMU) &&
>  		 amd_iommu_irq_ops.prepare() == 0)
>  		remap_ops = &amd_iommu_irq_ops;
> -	else if (IS_ENABLED(CONFIG_HYPERV_IOMMU) &&
> +	else if (IS_ENABLED(CONFIG_HYPERV) &&
>  		 hyperv_irq_remap_ops.prepare() == 0)
>  		remap_ops = &hyperv_irq_remap_ops;
>  	else

Re: [PATCH V3 01/11] iommu/hyperv: Rename hyperv-iommu.c to hyperv-irq.c

[Mukesh R]

On 5/12/26 16:46, Jacob Pan wrote:
> Hi Mukesh,
> 
> On Mon, 11 May 2026 19:02:49 -0700
> Mukesh R <mrathor@linux.microsoft.com> wrote:
> 
>> This file actually implements irq remapping, so rename to more
>> appropriate hyperv-irq.c. A new file to implement hyperv iommu will
>> be introduced later.  Also, it should not be tied to HYPERV_IOMMU,
>> but to CONFIG_HYPERV and IRQ_REMAP. The file already has #ifdef
>> CONFIG_IRQ_REMAP.
>>
>> Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
>> Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
>> ---
>>   MAINTAINERS                                    | 2 +-
>>   drivers/iommu/Makefile                         | 2 +-
>>   drivers/iommu/{hyperv-iommu.c => hyperv-irq.c} | 6 +++---
> Given that we have multiple Hyper-V IOMMU-related files ? this renamed
> hyperv-irq.c, the existing hyperv-iommu code, iommu-root (this
> series) and the recently posted guest pvIOMMU driver ? should we create
> a drivers/iommu/hyperv/ directory to consolidate them?

This came up briefly during synup with arm64 devs whether to split
the file into arch specific and common. We decided to wait till arm is
working so we can tell how intrusive the #ifdefs are. We can decide as
part of the arm port patches. I am ok also if you want to do it as part
of the pv-iommu patches as follow up once this is merged.

Thanks,
-Mukesh

>>   drivers/iommu/irq_remapping.c                  | 2 +-
>>   4 files changed, 6 insertions(+), 6 deletions(-)
>>   rename drivers/iommu/{hyperv-iommu.c => hyperv-irq.c} (99%)
>>
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index d1cc0e12fe1f..f803a6a38fee 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -11914,7 +11914,7 @@ F:	drivers/clocksource/hyperv_timer.c
>>   F:	drivers/hid/hid-hyperv.c
>>   F:	drivers/hv/
>>   F:	drivers/input/serio/hyperv-keyboard.c
>> -F:	drivers/iommu/hyperv-iommu.c
>> +F:	drivers/iommu/hyperv-irq.c
>>   F:	drivers/net/ethernet/microsoft/
>>   F:	drivers/net/hyperv/
>>   F:	drivers/pci/controller/pci-hyperv-intf.c
>> diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
>> index 0275821f4ef9..335ea77cced6 100644
>> --- a/drivers/iommu/Makefile
>> +++ b/drivers/iommu/Makefile
>> @@ -30,7 +30,7 @@ obj-$(CONFIG_TEGRA_IOMMU_SMMU) += tegra-smmu.o
>>   obj-$(CONFIG_EXYNOS_IOMMU) += exynos-iommu.o
>>   obj-$(CONFIG_FSL_PAMU) += fsl_pamu.o fsl_pamu_domain.o
>>   obj-$(CONFIG_S390_IOMMU) += s390-iommu.o
>> -obj-$(CONFIG_HYPERV_IOMMU) += hyperv-iommu.o
>> +obj-$(CONFIG_HYPERV) += hyperv-irq.o
>>   obj-$(CONFIG_VIRTIO_IOMMU) += virtio-iommu.o
>>   obj-$(CONFIG_IOMMU_SVA) += iommu-sva.o
>>   obj-$(CONFIG_IOMMU_IOPF) += io-pgfault.o
>> diff --git a/drivers/iommu/hyperv-iommu.c b/drivers/iommu/hyperv-irq.c
>> similarity index 99%
>> rename from drivers/iommu/hyperv-iommu.c
>> rename to drivers/iommu/hyperv-irq.c
>> index 479103261ae6..d11076f906fb 100644
>> --- a/drivers/iommu/hyperv-iommu.c
>> +++ b/drivers/iommu/hyperv-irq.c
>> @@ -8,6 +8,8 @@
>>    * Author : Lan Tianyu <Tianyu.Lan@microsoft.com>
>>    */
>>   
>> +#ifdef CONFIG_IRQ_REMAP
>> +
>>   #include <linux/types.h>
>>   #include <linux/interrupt.h>
>>   #include <linux/irq.h>
>> @@ -24,8 +26,6 @@
>>   
>>   #include "irq_remapping.h"
>>   
>> -#ifdef CONFIG_IRQ_REMAP
>> -
>>   /*
>>    * According 82093AA IO-APIC spec , IO APIC has a 24-entry Interrupt
>>    * Redirection Table. Hyper-V exposes one single IO-APIC and so
>> define @@ -331,4 +331,4 @@ static const struct irq_domain_ops
>> hyperv_root_ir_domain_ops = { .free = hyperv_root_irq_remapping_free,
>>   };
>>   
>> -#endif
>> +#endif  /* CONFIG_IRQ_REMAP */
>> diff --git a/drivers/iommu/irq_remapping.c
>> b/drivers/iommu/irq_remapping.c index c2443659812a..41bf65e4ea88
>> 100644 --- a/drivers/iommu/irq_remapping.c
>> +++ b/drivers/iommu/irq_remapping.c
>> @@ -108,7 +108,7 @@ int __init irq_remapping_prepare(void)
>>   	else if (IS_ENABLED(CONFIG_AMD_IOMMU) &&
>>   		 amd_iommu_irq_ops.prepare() == 0)
>>   		remap_ops = &amd_iommu_irq_ops;
>> -	else if (IS_ENABLED(CONFIG_HYPERV_IOMMU) &&
>> +	else if (IS_ENABLED(CONFIG_HYPERV) &&
>>   		 hyperv_irq_remap_ops.prepare() == 0)
>>   		remap_ops = &hyperv_irq_remap_ops;
>>   	else

RE: [PATCH V3 01/11] iommu/hyperv: Rename hyperv-iommu.c to hyperv-irq.c

[Michael Kelley]

From: Jacob Pan <jacob.pan@linux.microsoft.com> Sent: Tuesday, May 12, 2026 4:46 PM
> 
> Hi Mukesh,
> 
> On Mon, 11 May 2026 19:02:49 -0700
> Mukesh R <mrathor@linux.microsoft.com> wrote:
> 
> > This file actually implements irq remapping, so rename to more
> > appropriate hyperv-irq.c. A new file to implement hyperv iommu will
> > be introduced later.  Also, it should not be tied to HYPERV_IOMMU,
> > but to CONFIG_HYPERV and IRQ_REMAP. The file already has #ifdef
> > CONFIG_IRQ_REMAP.
> >
> > Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
> > Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
> > ---
> >  MAINTAINERS                                    | 2 +-
> >  drivers/iommu/Makefile                         | 2 +-
> >  drivers/iommu/{hyperv-iommu.c => hyperv-irq.c} | 6 +++---
>
> Given that we have multiple Hyper-V IOMMU-related files — this renamed
> hyperv-irq.c, the existing hyperv-iommu code, iommu-root (this
> series) and the recently posted guest pvIOMMU driver — should we create
> a drivers/iommu/hyperv/ directory to consolidate them?

Patch 1/4 in the guest pvIOMMU driver [1] that was recently posted by
Yu Zhang does as you suggest.

Michael

[1] https://lore.kernel.org/linux-hyperv/20260511162408.1180069-1-zhangyu1@linux.microsoft.com/

> 
> >  drivers/iommu/irq_remapping.c                  | 2 +-
> >  4 files changed, 6 insertions(+), 6 deletions(-)
> >  rename drivers/iommu/{hyperv-iommu.c => hyperv-irq.c} (99%)
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index d1cc0e12fe1f..f803a6a38fee 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -11914,7 +11914,7 @@ F:	drivers/clocksource/hyperv_timer.c
> >  F:	drivers/hid/hid-hyperv.c
> >  F:	drivers/hv/
> >  F:	drivers/input/serio/hyperv-keyboard.c
> > -F:	drivers/iommu/hyperv-iommu.c
> > +F:	drivers/iommu/hyperv-irq.c
> >  F:	drivers/net/ethernet/microsoft/
> >  F:	drivers/net/hyperv/
> >  F:	drivers/pci/controller/pci-hyperv-intf.c
> > diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
> > index 0275821f4ef9..335ea77cced6 100644
> > --- a/drivers/iommu/Makefile
> > +++ b/drivers/iommu/Makefile
> > @@ -30,7 +30,7 @@ obj-$(CONFIG_TEGRA_IOMMU_SMMU) += tegra-smmu.o
> >  obj-$(CONFIG_EXYNOS_IOMMU) += exynos-iommu.o
> >  obj-$(CONFIG_FSL_PAMU) += fsl_pamu.o fsl_pamu_domain.o
> >  obj-$(CONFIG_S390_IOMMU) += s390-iommu.o
> > -obj-$(CONFIG_HYPERV_IOMMU) += hyperv-iommu.o
> > +obj-$(CONFIG_HYPERV) += hyperv-irq.o
> >  obj-$(CONFIG_VIRTIO_IOMMU) += virtio-iommu.o
> >  obj-$(CONFIG_IOMMU_SVA) += iommu-sva.o
> >  obj-$(CONFIG_IOMMU_IOPF) += io-pgfault.o
> > diff --git a/drivers/iommu/hyperv-iommu.c b/drivers/iommu/hyperv-irq.c
> > similarity index 99%
> > rename from drivers/iommu/hyperv-iommu.c
> > rename to drivers/iommu/hyperv-irq.c
> > index 479103261ae6..d11076f906fb 100644
> > --- a/drivers/iommu/hyperv-iommu.c
> > +++ b/drivers/iommu/hyperv-irq.c
> > @@ -8,6 +8,8 @@
> >   * Author : Lan Tianyu <Tianyu.Lan@microsoft.com>
> >   */
> >
> > +#ifdef CONFIG_IRQ_REMAP
> > +
> >  #include <linux/types.h>
> >  #include <linux/interrupt.h>
> >  #include <linux/irq.h>
> > @@ -24,8 +26,6 @@
> >
> >  #include "irq_remapping.h"
> >
> > -#ifdef CONFIG_IRQ_REMAP
> > -
> >  /*
> >   * According 82093AA IO-APIC spec , IO APIC has a 24-entry Interrupt
> >   * Redirection Table. Hyper-V exposes one single IO-APIC and so
> > define @@ -331,4 +331,4 @@ static const struct irq_domain_ops
> > hyperv_root_ir_domain_ops = { .free = hyperv_root_irq_remapping_free,
> >  };
> >
> > -#endif
> > +#endif  /* CONFIG_IRQ_REMAP */
> > diff --git a/drivers/iommu/irq_remapping.c
> > b/drivers/iommu/irq_remapping.c index c2443659812a..41bf65e4ea88
> > 100644 --- a/drivers/iommu/irq_remapping.c
> > +++ b/drivers/iommu/irq_remapping.c
> > @@ -108,7 +108,7 @@ int __init irq_remapping_prepare(void)
> >  	else if (IS_ENABLED(CONFIG_AMD_IOMMU) &&
> >  		 amd_iommu_irq_ops.prepare() == 0)
> >  		remap_ops = &amd_iommu_irq_ops;
> > -	else if (IS_ENABLED(CONFIG_HYPERV_IOMMU) &&
> > +	else if (IS_ENABLED(CONFIG_HYPERV) &&
> >  		 hyperv_irq_remap_ops.prepare() == 0)
> >  		remap_ops = &hyperv_irq_remap_ops;
> >  	else
> 

[PATCH V3 02/11] x86/hyperv: Cosmetic changes in irqdomain.c for readability

[Mukesh R]

Make cosmetic changes:
 o Rename struct pci_dev *dev to *pdev since there are cases of
   struct device *dev in the file and all over the kernel
 o Rename hv_build_pci_dev_id to hv_build_devid_type_pci in anticipation
   of building different types of device IDs
 o Fix checkpatch.pl issues with return and extraneous printk
 o Replace spaces with tabs
 o Rename struct hv_devid *xxx to struct hv_devid *hv_devid given code
   paths involve many types of device IDs
 o Fix indentation in a large if block by using goto.

There are no functional changes.

Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
---
 arch/x86/hyperv/irqdomain.c | 198 +++++++++++++++++++-----------------
 1 file changed, 104 insertions(+), 94 deletions(-)

diff --git a/arch/x86/hyperv/irqdomain.c b/arch/x86/hyperv/irqdomain.c
index 365e364268d9..b3ad50a874dc 100644
--- a/arch/x86/hyperv/irqdomain.c
+++ b/arch/x86/hyperv/irqdomain.c
@@ -1,5 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0
-
 /*
  * Irqdomain for Linux to run as the root partition on Microsoft Hypervisor.
  *
@@ -14,8 +13,8 @@
 #include <linux/irqchip/irq-msi-lib.h>
 #include <asm/mshyperv.h>
 
-static int hv_map_interrupt(union hv_device_id device_id, bool level,
-		int cpu, int vector, struct hv_interrupt_entry *entry)
+static int hv_map_interrupt(union hv_device_id hv_devid, bool level,
+		int cpu, int vector, struct hv_interrupt_entry *ret_entry)
 {
 	struct hv_input_map_device_interrupt *input;
 	struct hv_output_map_device_interrupt *output;
@@ -32,7 +31,7 @@ static int hv_map_interrupt(union hv_device_id device_id, bool level,
 	intr_desc = &input->interrupt_descriptor;
 	memset(input, 0, sizeof(*input));
 	input->partition_id = hv_current_partition_id;
-	input->device_id = device_id.as_uint64;
+	input->device_id = hv_devid.as_uint64;
 	intr_desc->interrupt_type = HV_X64_INTERRUPT_TYPE_FIXED;
 	intr_desc->vector_count = 1;
 	intr_desc->target.vector = vector;
@@ -44,7 +43,7 @@ static int hv_map_interrupt(union hv_device_id device_id, bool level,
 
 	intr_desc->target.vp_set.valid_bank_mask = 0;
 	intr_desc->target.vp_set.format = HV_GENERIC_SET_SPARSE_4K;
-	nr_bank = cpumask_to_vpset(&(intr_desc->target.vp_set), cpumask_of(cpu));
+	nr_bank = cpumask_to_vpset(&intr_desc->target.vp_set, cpumask_of(cpu));
 	if (nr_bank < 0) {
 		local_irq_restore(flags);
 		pr_err("%s: unable to generate VP set\n", __func__);
@@ -61,7 +60,7 @@ static int hv_map_interrupt(union hv_device_id device_id, bool level,
 
 	status = hv_do_rep_hypercall(HVCALL_MAP_DEVICE_INTERRUPT, 0, var_size,
 			input, output);
-	*entry = output->interrupt_entry;
+	*ret_entry = output->interrupt_entry;
 
 	local_irq_restore(flags);
 
@@ -71,21 +70,19 @@ static int hv_map_interrupt(union hv_device_id device_id, bool level,
 	return hv_result_to_errno(status);
 }
 
-static int hv_unmap_interrupt(u64 id, struct hv_interrupt_entry *old_entry)
+static int hv_unmap_interrupt(u64 id, struct hv_interrupt_entry *irq_entry)
 {
 	unsigned long flags;
 	struct hv_input_unmap_device_interrupt *input;
-	struct hv_interrupt_entry *intr_entry;
 	u64 status;
 
 	local_irq_save(flags);
 	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
 
 	memset(input, 0, sizeof(*input));
-	intr_entry = &input->interrupt_entry;
 	input->partition_id = hv_current_partition_id;
 	input->device_id = id;
-	*intr_entry = *old_entry;
+	input->interrupt_entry = *irq_entry;
 
 	status = hv_do_hypercall(HVCALL_UNMAP_DEVICE_INTERRUPT, input, NULL);
 	local_irq_restore(flags);
@@ -115,67 +112,71 @@ static int get_rid_cb(struct pci_dev *pdev, u16 alias, void *data)
 	return 0;
 }
 
-static union hv_device_id hv_build_pci_dev_id(struct pci_dev *dev)
+static union hv_device_id hv_build_devid_type_pci(struct pci_dev *pdev)
 {
-	union hv_device_id dev_id;
+	int pos;
+	union hv_device_id hv_devid;
 	struct rid_data data = {
 		.bridge = NULL,
-		.rid = PCI_DEVID(dev->bus->number, dev->devfn)
+		.rid = PCI_DEVID(pdev->bus->number, pdev->devfn)
 	};
 
-	pci_for_each_dma_alias(dev, get_rid_cb, &data);
+	pci_for_each_dma_alias(pdev, get_rid_cb, &data);
 
-	dev_id.as_uint64 = 0;
-	dev_id.device_type = HV_DEVICE_TYPE_PCI;
-	dev_id.pci.segment = pci_domain_nr(dev->bus);
+	hv_devid.as_uint64 = 0;
+	hv_devid.device_type = HV_DEVICE_TYPE_PCI;
+	hv_devid.pci.segment = pci_domain_nr(pdev->bus);
 
-	dev_id.pci.bdf.bus = PCI_BUS_NUM(data.rid);
-	dev_id.pci.bdf.device = PCI_SLOT(data.rid);
-	dev_id.pci.bdf.function = PCI_FUNC(data.rid);
-	dev_id.pci.source_shadow = HV_SOURCE_SHADOW_NONE;
+	hv_devid.pci.bdf.bus = PCI_BUS_NUM(data.rid);
+	hv_devid.pci.bdf.device = PCI_SLOT(data.rid);
+	hv_devid.pci.bdf.function = PCI_FUNC(data.rid);
+	hv_devid.pci.source_shadow = HV_SOURCE_SHADOW_NONE;
 
-	if (data.bridge) {
-		int pos;
+	if (data.bridge == NULL)
+		goto out;
 
-		/*
-		 * Microsoft Hypervisor requires a bus range when the bridge is
-		 * running in PCI-X mode.
-		 *
-		 * To distinguish conventional vs PCI-X bridge, we can check
-		 * the bridge's PCI-X Secondary Status Register, Secondary Bus
-		 * Mode and Frequency bits. See PCI Express to PCI/PCI-X Bridge
-		 * Specification Revision 1.0 5.2.2.1.3.
-		 *
-		 * Value zero means it is in conventional mode, otherwise it is
-		 * in PCI-X mode.
-		 */
+	/*
+	 * Microsoft Hypervisor requires a bus range when the bridge is
+	 * running in PCI-X mode.
+	 *
+	 * To distinguish conventional vs PCI-X bridge, we can check
+	 * the bridge's PCI-X Secondary Status Register, Secondary Bus
+	 * Mode and Frequency bits. See PCI Express to PCI/PCI-X Bridge
+	 * Specification Revision 1.0 5.2.2.1.3.
+	 *
+	 * Value zero means it is in conventional mode, otherwise it is
+	 * in PCI-X mode.
+	 */
 
-		pos = pci_find_capability(data.bridge, PCI_CAP_ID_PCIX);
-		if (pos) {
-			u16 status;
+	pos = pci_find_capability(data.bridge, PCI_CAP_ID_PCIX);
+	if (pos) {
+		u16 status;
 
-			pci_read_config_word(data.bridge, pos +
-					PCI_X_BRIDGE_SSTATUS, &status);
+		pci_read_config_word(data.bridge, pos + PCI_X_BRIDGE_SSTATUS,
+				     &status);
 
-			if (status & PCI_X_SSTATUS_FREQ) {
-				/* Non-zero, PCI-X mode */
-				u8 sec_bus, sub_bus;
+		if (status & PCI_X_SSTATUS_FREQ) {
+			/* Non-zero, PCI-X mode */
+			u8 sec_bus, sub_bus;
 
-				dev_id.pci.source_shadow = HV_SOURCE_SHADOW_BRIDGE_BUS_RANGE;
+			hv_devid.pci.source_shadow =
+					     HV_SOURCE_SHADOW_BRIDGE_BUS_RANGE;
 
-				pci_read_config_byte(data.bridge, PCI_SECONDARY_BUS, &sec_bus);
-				dev_id.pci.shadow_bus_range.secondary_bus = sec_bus;
-				pci_read_config_byte(data.bridge, PCI_SUBORDINATE_BUS, &sub_bus);
-				dev_id.pci.shadow_bus_range.subordinate_bus = sub_bus;
-			}
+			pci_read_config_byte(data.bridge, PCI_SECONDARY_BUS,
+					     &sec_bus);
+			hv_devid.pci.shadow_bus_range.secondary_bus = sec_bus;
+			pci_read_config_byte(data.bridge, PCI_SUBORDINATE_BUS,
+					     &sub_bus);
+			hv_devid.pci.shadow_bus_range.subordinate_bus = sub_bus;
 		}
 	}
 
-	return dev_id;
+out:
+	return hv_devid;
 }
 
-/**
- * hv_map_msi_interrupt() - "Map" the MSI IRQ in the hypervisor.
+/*
+ * hv_map_msi_interrupt() - Map the MSI IRQ in the hypervisor.
  * @data:      Describes the IRQ
  * @out_entry: Hypervisor (MSI) interrupt entry (can be NULL)
  *
@@ -188,22 +189,23 @@ int hv_map_msi_interrupt(struct irq_data *data,
 {
 	struct irq_cfg *cfg = irqd_cfg(data);
 	struct hv_interrupt_entry dummy;
-	union hv_device_id device_id;
+	union hv_device_id hv_devid;
 	struct msi_desc *msidesc;
-	struct pci_dev *dev;
+	struct pci_dev *pdev;
 	int cpu;
 
 	msidesc = irq_data_get_msi_desc(data);
-	dev = msi_desc_to_pci_dev(msidesc);
-	device_id = hv_build_pci_dev_id(dev);
+	pdev = msi_desc_to_pci_dev(msidesc);
+	hv_devid = hv_build_devid_type_pci(pdev);
 	cpu = cpumask_first(irq_data_get_effective_affinity_mask(data));
 
-	return hv_map_interrupt(device_id, false, cpu, cfg->vector,
+	return hv_map_interrupt(hv_devid, false, cpu, cfg->vector,
 				out_entry ? out_entry : &dummy);
 }
 EXPORT_SYMBOL_GPL(hv_map_msi_interrupt);
 
-static inline void entry_to_msi_msg(struct hv_interrupt_entry *entry, struct msi_msg *msg)
+static void entry_to_msi_msg(struct hv_interrupt_entry *entry,
+			     struct msi_msg *msg)
 {
 	/* High address is always 0 */
 	msg->address_hi = 0;
@@ -211,17 +213,19 @@ static inline void entry_to_msi_msg(struct hv_interrupt_entry *entry, struct msi
 	msg->data = entry->msi_entry.data.as_uint32;
 }
 
-static int hv_unmap_msi_interrupt(struct pci_dev *dev, struct hv_interrupt_entry *old_entry);
+static int hv_unmap_msi_interrupt(struct pci_dev *pdev,
+				  struct hv_interrupt_entry *irq_entry);
+
 static void hv_irq_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 {
 	struct hv_interrupt_entry *stored_entry;
 	struct irq_cfg *cfg = irqd_cfg(data);
 	struct msi_desc *msidesc;
-	struct pci_dev *dev;
+	struct pci_dev *pdev;
 	int ret;
 
 	msidesc = irq_data_get_msi_desc(data);
-	dev = msi_desc_to_pci_dev(msidesc);
+	pdev = msi_desc_to_pci_dev(msidesc);
 
 	if (!cfg) {
 		pr_debug("%s: cfg is NULL", __func__);
@@ -240,7 +244,7 @@ static void hv_irq_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 		stored_entry = data->chip_data;
 		data->chip_data = NULL;
 
-		ret = hv_unmap_msi_interrupt(dev, stored_entry);
+		ret = hv_unmap_msi_interrupt(pdev, stored_entry);
 
 		kfree(stored_entry);
 
@@ -249,10 +253,8 @@ static void hv_irq_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 	}
 
 	stored_entry = kzalloc_obj(*stored_entry, GFP_ATOMIC);
-	if (!stored_entry) {
-		pr_debug("%s: failed to allocate chip data\n", __func__);
+	if (!stored_entry)
 		return;
-	}
 
 	ret = hv_map_msi_interrupt(data, stored_entry);
 	if (ret) {
@@ -262,18 +264,21 @@ static void hv_irq_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 
 	data->chip_data = stored_entry;
 	entry_to_msi_msg(data->chip_data, msg);
-
-	return;
 }
 
-static int hv_unmap_msi_interrupt(struct pci_dev *dev, struct hv_interrupt_entry *old_entry)
+static int hv_unmap_msi_interrupt(struct pci_dev *pdev,
+				  struct hv_interrupt_entry *irq_entry)
 {
-	return hv_unmap_interrupt(hv_build_pci_dev_id(dev).as_uint64, old_entry);
+	union hv_device_id hv_devid;
+
+	hv_devid = hv_build_devid_type_pci(pdev);
+	return hv_unmap_interrupt(hv_devid.as_uint64, irq_entry);
 }
 
-static void hv_teardown_msi_irq(struct pci_dev *dev, struct irq_data *irqd)
+/* NB: during map, hv_interrupt_entry is saved via data->chip_data */
+static void hv_teardown_msi_irq(struct pci_dev *pdev, struct irq_data *irqd)
 {
-	struct hv_interrupt_entry old_entry;
+	struct hv_interrupt_entry irq_entry;
 	struct msi_msg msg;
 
 	if (!irqd->chip_data) {
@@ -281,13 +286,13 @@ static void hv_teardown_msi_irq(struct pci_dev *dev, struct irq_data *irqd)
 		return;
 	}
 
-	old_entry = *(struct hv_interrupt_entry *)irqd->chip_data;
-	entry_to_msi_msg(&old_entry, &msg);
+	irq_entry = *(struct hv_interrupt_entry *)irqd->chip_data;
+	entry_to_msi_msg(&irq_entry, &msg);
 
 	kfree(irqd->chip_data);
 	irqd->chip_data = NULL;
 
-	(void)hv_unmap_msi_interrupt(dev, &old_entry);
+	(void)hv_unmap_msi_interrupt(pdev, &irq_entry);
 }
 
 /*
@@ -302,7 +307,8 @@ static struct irq_chip hv_pci_msi_controller = {
 };
 
 static bool hv_init_dev_msi_info(struct device *dev, struct irq_domain *domain,
-				 struct irq_domain *real_parent, struct msi_domain_info *info)
+				 struct irq_domain *real_parent,
+				 struct msi_domain_info *info)
 {
 	struct irq_chip *chip = info->chip;
 
@@ -317,7 +323,8 @@ static bool hv_init_dev_msi_info(struct device *dev, struct irq_domain *domain,
 }
 
 #define HV_MSI_FLAGS_SUPPORTED	(MSI_GENERIC_FLAGS_MASK | MSI_FLAG_PCI_MSIX)
-#define HV_MSI_FLAGS_REQUIRED	(MSI_FLAG_USE_DEF_DOM_OPS | MSI_FLAG_USE_DEF_CHIP_OPS)
+#define HV_MSI_FLAGS_REQUIRED	(MSI_FLAG_USE_DEF_DOM_OPS |	\
+				 MSI_FLAG_USE_DEF_CHIP_OPS)
 
 static struct msi_parent_ops hv_msi_parent_ops = {
 	.supported_flags	= HV_MSI_FLAGS_SUPPORTED,
@@ -329,14 +336,14 @@ static struct msi_parent_ops hv_msi_parent_ops = {
 	.init_dev_msi_info	= hv_init_dev_msi_info,
 };
 
-static int hv_msi_domain_alloc(struct irq_domain *d, unsigned int virq, unsigned int nr_irqs,
-			       void *arg)
+/* Allocate nr_irqs IRQs for the given irq domain */
+static int hv_msi_domain_alloc(struct irq_domain *d, unsigned int virq,
+			       unsigned int nr_irqs, void *arg)
 {
 	/*
-	 * TODO: The allocation bits of hv_irq_compose_msi_msg(), i.e. everything except
-	 * entry_to_msi_msg() should be in here.
+	 * TODO: The allocation bits of hv_irq_compose_msi_msg(), i.e.
+	 *	 everything except entry_to_msi_msg() should be in here.
 	 */
-
 	int ret;
 
 	ret = irq_domain_alloc_irqs_parent(d, virq, nr_irqs, arg);
@@ -344,13 +351,15 @@ static int hv_msi_domain_alloc(struct irq_domain *d, unsigned int virq, unsigned
 		return ret;
 
 	for (int i = 0; i < nr_irqs; ++i) {
-		irq_domain_set_info(d, virq + i, 0, &hv_pci_msi_controller, NULL,
-				    handle_edge_irq, NULL, "edge");
+		irq_domain_set_info(d, virq + i, 0, &hv_pci_msi_controller,
+				    NULL, handle_edge_irq, NULL, "edge");
 	}
+
 	return 0;
 }
 
-static void hv_msi_domain_free(struct irq_domain *d, unsigned int virq, unsigned int nr_irqs)
+static void hv_msi_domain_free(struct irq_domain *d, unsigned int virq,
+			       unsigned int nr_irqs)
 {
 	for (int i = 0; i < nr_irqs; ++i) {
 		struct irq_data *irqd = irq_domain_get_irq_data(d, virq);
@@ -362,6 +371,7 @@ static void hv_msi_domain_free(struct irq_domain *d, unsigned int virq, unsigned
 
 		hv_teardown_msi_irq(to_pci_dev(desc->dev), irqd);
 	}
+
 	irq_domain_free_irqs_top(d, virq, nr_irqs);
 }
 
@@ -394,25 +404,25 @@ struct irq_domain * __init hv_create_pci_msi_domain(void)
 
 int hv_unmap_ioapic_interrupt(int ioapic_id, struct hv_interrupt_entry *entry)
 {
-	union hv_device_id device_id;
+	union hv_device_id hv_devid;
 
-	device_id.as_uint64 = 0;
-	device_id.device_type = HV_DEVICE_TYPE_IOAPIC;
-	device_id.ioapic.ioapic_id = (u8)ioapic_id;
+	hv_devid.as_uint64 = 0;
+	hv_devid.device_type = HV_DEVICE_TYPE_IOAPIC;
+	hv_devid.ioapic.ioapic_id = (u8)ioapic_id;
 
-	return hv_unmap_interrupt(device_id.as_uint64, entry);
+	return hv_unmap_interrupt(hv_devid.as_uint64, entry);
 }
 EXPORT_SYMBOL_GPL(hv_unmap_ioapic_interrupt);
 
 int hv_map_ioapic_interrupt(int ioapic_id, bool level, int cpu, int vector,
 		struct hv_interrupt_entry *entry)
 {
-	union hv_device_id device_id;
+	union hv_device_id hv_devid;
 
-	device_id.as_uint64 = 0;
-	device_id.device_type = HV_DEVICE_TYPE_IOAPIC;
-	device_id.ioapic.ioapic_id = (u8)ioapic_id;
+	hv_devid.as_uint64 = 0;
+	hv_devid.device_type = HV_DEVICE_TYPE_IOAPIC;
+	hv_devid.ioapic.ioapic_id = (u8)ioapic_id;
 
-	return hv_map_interrupt(device_id, level, cpu, vector, entry);
+	return hv_map_interrupt(hv_devid, level, cpu, vector, entry);
 }
 EXPORT_SYMBOL_GPL(hv_map_ioapic_interrupt);
-- 
2.51.2.vfs.0.1

Re: [PATCH V3 02/11] x86/hyperv: Cosmetic changes in irqdomain.c for readability

[Souradeep Chakrabarti]

On Mon, May 11, 2026 at 07:02:50PM -0700, Mukesh R wrote:
> Make cosmetic changes:
>  o Rename struct pci_dev *dev to *pdev since there are cases of
>    struct device *dev in the file and all over the kernel
>  o Rename hv_build_pci_dev_id to hv_build_devid_type_pci in anticipation
>    of building different types of device IDs
>  o Fix checkpatch.pl issues with return and extraneous printk
>  o Replace spaces with tabs
>  o Rename struct hv_devid *xxx to struct hv_devid *hv_devid given code
>    paths involve many types of device IDs
>  o Fix indentation in a large if block by using goto.
> 
> There are no functional changes.
> 
> Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
Reviewed-by: Souradeep Chakrabarti <schakrabarti@linux.microsoft.com>
> Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
> ---
>  arch/x86/hyperv/irqdomain.c | 198 +++++++++++++++++++-----------------
>  1 file changed, 104 insertions(+), 94 deletions(-)
> 
> diff --git a/arch/x86/hyperv/irqdomain.c b/arch/x86/hyperv/irqdomain.c
> index 365e364268d9..b3ad50a874dc 100644
> --- a/arch/x86/hyperv/irqdomain.c
> +++ b/arch/x86/hyperv/irqdomain.c
> @@ -1,5 +1,4 @@
>  // SPDX-License-Identifier: GPL-2.0
> -
>  /*
>   * Irqdomain for Linux to run as the root partition on Microsoft Hypervisor.
>   *
> @@ -14,8 +13,8 @@
>  #include <linux/irqchip/irq-msi-lib.h>
>  #include <asm/mshyperv.h>
>  
> -static int hv_map_interrupt(union hv_device_id device_id, bool level,
> -		int cpu, int vector, struct hv_interrupt_entry *entry)
> +static int hv_map_interrupt(union hv_device_id hv_devid, bool level,
> +		int cpu, int vector, struct hv_interrupt_entry *ret_entry)
>  {
>  	struct hv_input_map_device_interrupt *input;
>  	struct hv_output_map_device_interrupt *output;
> @@ -32,7 +31,7 @@ static int hv_map_interrupt(union hv_device_id device_id, bool level,
>  	intr_desc = &input->interrupt_descriptor;
>  	memset(input, 0, sizeof(*input));
>  	input->partition_id = hv_current_partition_id;
> -	input->device_id = device_id.as_uint64;
> +	input->device_id = hv_devid.as_uint64;
>  	intr_desc->interrupt_type = HV_X64_INTERRUPT_TYPE_FIXED;
>  	intr_desc->vector_count = 1;
>  	intr_desc->target.vector = vector;
> @@ -44,7 +43,7 @@ static int hv_map_interrupt(union hv_device_id device_id, bool level,
>  
>  	intr_desc->target.vp_set.valid_bank_mask = 0;
>  	intr_desc->target.vp_set.format = HV_GENERIC_SET_SPARSE_4K;
> -	nr_bank = cpumask_to_vpset(&(intr_desc->target.vp_set), cpumask_of(cpu));
> +	nr_bank = cpumask_to_vpset(&intr_desc->target.vp_set, cpumask_of(cpu));
>  	if (nr_bank < 0) {
>  		local_irq_restore(flags);
>  		pr_err("%s: unable to generate VP set\n", __func__);
> @@ -61,7 +60,7 @@ static int hv_map_interrupt(union hv_device_id device_id, bool level,
>  
>  	status = hv_do_rep_hypercall(HVCALL_MAP_DEVICE_INTERRUPT, 0, var_size,
>  			input, output);
> -	*entry = output->interrupt_entry;
> +	*ret_entry = output->interrupt_entry;
>  
>  	local_irq_restore(flags);
>  
> @@ -71,21 +70,19 @@ static int hv_map_interrupt(union hv_device_id device_id, bool level,
>  	return hv_result_to_errno(status);
>  }
>  
> -static int hv_unmap_interrupt(u64 id, struct hv_interrupt_entry *old_entry)
> +static int hv_unmap_interrupt(u64 id, struct hv_interrupt_entry *irq_entry)
>  {
>  	unsigned long flags;
>  	struct hv_input_unmap_device_interrupt *input;
> -	struct hv_interrupt_entry *intr_entry;
>  	u64 status;
>  
>  	local_irq_save(flags);
>  	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
>  
>  	memset(input, 0, sizeof(*input));
> -	intr_entry = &input->interrupt_entry;
>  	input->partition_id = hv_current_partition_id;
>  	input->device_id = id;
> -	*intr_entry = *old_entry;
> +	input->interrupt_entry = *irq_entry;
>  
>  	status = hv_do_hypercall(HVCALL_UNMAP_DEVICE_INTERRUPT, input, NULL);
>  	local_irq_restore(flags);
> @@ -115,67 +112,71 @@ static int get_rid_cb(struct pci_dev *pdev, u16 alias, void *data)
>  	return 0;
>  }
>  
> -static union hv_device_id hv_build_pci_dev_id(struct pci_dev *dev)
> +static union hv_device_id hv_build_devid_type_pci(struct pci_dev *pdev)
>  {
> -	union hv_device_id dev_id;
> +	int pos;
> +	union hv_device_id hv_devid;
>  	struct rid_data data = {
>  		.bridge = NULL,
> -		.rid = PCI_DEVID(dev->bus->number, dev->devfn)
> +		.rid = PCI_DEVID(pdev->bus->number, pdev->devfn)
>  	};
>  
> -	pci_for_each_dma_alias(dev, get_rid_cb, &data);
> +	pci_for_each_dma_alias(pdev, get_rid_cb, &data);
>  
> -	dev_id.as_uint64 = 0;
> -	dev_id.device_type = HV_DEVICE_TYPE_PCI;
> -	dev_id.pci.segment = pci_domain_nr(dev->bus);
> +	hv_devid.as_uint64 = 0;
> +	hv_devid.device_type = HV_DEVICE_TYPE_PCI;
> +	hv_devid.pci.segment = pci_domain_nr(pdev->bus);
>  
> -	dev_id.pci.bdf.bus = PCI_BUS_NUM(data.rid);
> -	dev_id.pci.bdf.device = PCI_SLOT(data.rid);
> -	dev_id.pci.bdf.function = PCI_FUNC(data.rid);
> -	dev_id.pci.source_shadow = HV_SOURCE_SHADOW_NONE;
> +	hv_devid.pci.bdf.bus = PCI_BUS_NUM(data.rid);
> +	hv_devid.pci.bdf.device = PCI_SLOT(data.rid);
> +	hv_devid.pci.bdf.function = PCI_FUNC(data.rid);
> +	hv_devid.pci.source_shadow = HV_SOURCE_SHADOW_NONE;
>  
> -	if (data.bridge) {
> -		int pos;
> +	if (data.bridge == NULL)
> +		goto out;
>  
> -		/*
> -		 * Microsoft Hypervisor requires a bus range when the bridge is
> -		 * running in PCI-X mode.
> -		 *
> -		 * To distinguish conventional vs PCI-X bridge, we can check
> -		 * the bridge's PCI-X Secondary Status Register, Secondary Bus
> -		 * Mode and Frequency bits. See PCI Express to PCI/PCI-X Bridge
> -		 * Specification Revision 1.0 5.2.2.1.3.
> -		 *
> -		 * Value zero means it is in conventional mode, otherwise it is
> -		 * in PCI-X mode.
> -		 */
> +	/*
> +	 * Microsoft Hypervisor requires a bus range when the bridge is
> +	 * running in PCI-X mode.
> +	 *
> +	 * To distinguish conventional vs PCI-X bridge, we can check
> +	 * the bridge's PCI-X Secondary Status Register, Secondary Bus
> +	 * Mode and Frequency bits. See PCI Express to PCI/PCI-X Bridge
> +	 * Specification Revision 1.0 5.2.2.1.3.
> +	 *
> +	 * Value zero means it is in conventional mode, otherwise it is
> +	 * in PCI-X mode.
> +	 */
>  
> -		pos = pci_find_capability(data.bridge, PCI_CAP_ID_PCIX);
> -		if (pos) {
> -			u16 status;
> +	pos = pci_find_capability(data.bridge, PCI_CAP_ID_PCIX);
> +	if (pos) {
> +		u16 status;
>  
> -			pci_read_config_word(data.bridge, pos +
> -					PCI_X_BRIDGE_SSTATUS, &status);
> +		pci_read_config_word(data.bridge, pos + PCI_X_BRIDGE_SSTATUS,
> +				     &status);
>  
> -			if (status & PCI_X_SSTATUS_FREQ) {
> -				/* Non-zero, PCI-X mode */
> -				u8 sec_bus, sub_bus;
> +		if (status & PCI_X_SSTATUS_FREQ) {
> +			/* Non-zero, PCI-X mode */
> +			u8 sec_bus, sub_bus;
>  
> -				dev_id.pci.source_shadow = HV_SOURCE_SHADOW_BRIDGE_BUS_RANGE;
> +			hv_devid.pci.source_shadow =
> +					     HV_SOURCE_SHADOW_BRIDGE_BUS_RANGE;
>  
> -				pci_read_config_byte(data.bridge, PCI_SECONDARY_BUS, &sec_bus);
> -				dev_id.pci.shadow_bus_range.secondary_bus = sec_bus;
> -				pci_read_config_byte(data.bridge, PCI_SUBORDINATE_BUS, &sub_bus);
> -				dev_id.pci.shadow_bus_range.subordinate_bus = sub_bus;
> -			}
> +			pci_read_config_byte(data.bridge, PCI_SECONDARY_BUS,
> +					     &sec_bus);
> +			hv_devid.pci.shadow_bus_range.secondary_bus = sec_bus;
> +			pci_read_config_byte(data.bridge, PCI_SUBORDINATE_BUS,
> +					     &sub_bus);
> +			hv_devid.pci.shadow_bus_range.subordinate_bus = sub_bus;
>  		}
>  	}
>  
> -	return dev_id;
> +out:
> +	return hv_devid;
>  }
>  
> -/**
> - * hv_map_msi_interrupt() - "Map" the MSI IRQ in the hypervisor.
> +/*
> + * hv_map_msi_interrupt() - Map the MSI IRQ in the hypervisor.
>   * @data:      Describes the IRQ
>   * @out_entry: Hypervisor (MSI) interrupt entry (can be NULL)
>   *
> @@ -188,22 +189,23 @@ int hv_map_msi_interrupt(struct irq_data *data,
>  {
>  	struct irq_cfg *cfg = irqd_cfg(data);
>  	struct hv_interrupt_entry dummy;
> -	union hv_device_id device_id;
> +	union hv_device_id hv_devid;
>  	struct msi_desc *msidesc;
> -	struct pci_dev *dev;
> +	struct pci_dev *pdev;
>  	int cpu;
>  
>  	msidesc = irq_data_get_msi_desc(data);
> -	dev = msi_desc_to_pci_dev(msidesc);
> -	device_id = hv_build_pci_dev_id(dev);
> +	pdev = msi_desc_to_pci_dev(msidesc);
> +	hv_devid = hv_build_devid_type_pci(pdev);
>  	cpu = cpumask_first(irq_data_get_effective_affinity_mask(data));
>  
> -	return hv_map_interrupt(device_id, false, cpu, cfg->vector,
> +	return hv_map_interrupt(hv_devid, false, cpu, cfg->vector,
>  				out_entry ? out_entry : &dummy);
>  }
>  EXPORT_SYMBOL_GPL(hv_map_msi_interrupt);
>  
> -static inline void entry_to_msi_msg(struct hv_interrupt_entry *entry, struct msi_msg *msg)
> +static void entry_to_msi_msg(struct hv_interrupt_entry *entry,
> +			     struct msi_msg *msg)
>  {
>  	/* High address is always 0 */
>  	msg->address_hi = 0;
> @@ -211,17 +213,19 @@ static inline void entry_to_msi_msg(struct hv_interrupt_entry *entry, struct msi
>  	msg->data = entry->msi_entry.data.as_uint32;
>  }
>  
> -static int hv_unmap_msi_interrupt(struct pci_dev *dev, struct hv_interrupt_entry *old_entry);
> +static int hv_unmap_msi_interrupt(struct pci_dev *pdev,
> +				  struct hv_interrupt_entry *irq_entry);
> +
>  static void hv_irq_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
>  {
>  	struct hv_interrupt_entry *stored_entry;
>  	struct irq_cfg *cfg = irqd_cfg(data);
>  	struct msi_desc *msidesc;
> -	struct pci_dev *dev;
> +	struct pci_dev *pdev;
>  	int ret;
>  
>  	msidesc = irq_data_get_msi_desc(data);
> -	dev = msi_desc_to_pci_dev(msidesc);
> +	pdev = msi_desc_to_pci_dev(msidesc);
>  
>  	if (!cfg) {
>  		pr_debug("%s: cfg is NULL", __func__);
> @@ -240,7 +244,7 @@ static void hv_irq_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
>  		stored_entry = data->chip_data;
>  		data->chip_data = NULL;
>  
> -		ret = hv_unmap_msi_interrupt(dev, stored_entry);
> +		ret = hv_unmap_msi_interrupt(pdev, stored_entry);
>  
>  		kfree(stored_entry);
>  
> @@ -249,10 +253,8 @@ static void hv_irq_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
>  	}
>  
>  	stored_entry = kzalloc_obj(*stored_entry, GFP_ATOMIC);
> -	if (!stored_entry) {
> -		pr_debug("%s: failed to allocate chip data\n", __func__);
> +	if (!stored_entry)
>  		return;
> -	}
>  
>  	ret = hv_map_msi_interrupt(data, stored_entry);
>  	if (ret) {
> @@ -262,18 +264,21 @@ static void hv_irq_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
>  
>  	data->chip_data = stored_entry;
>  	entry_to_msi_msg(data->chip_data, msg);
> -
> -	return;
>  }
>  
> -static int hv_unmap_msi_interrupt(struct pci_dev *dev, struct hv_interrupt_entry *old_entry)
> +static int hv_unmap_msi_interrupt(struct pci_dev *pdev,
> +				  struct hv_interrupt_entry *irq_entry)
>  {
> -	return hv_unmap_interrupt(hv_build_pci_dev_id(dev).as_uint64, old_entry);
> +	union hv_device_id hv_devid;
> +
> +	hv_devid = hv_build_devid_type_pci(pdev);
> +	return hv_unmap_interrupt(hv_devid.as_uint64, irq_entry);
>  }
>  
> -static void hv_teardown_msi_irq(struct pci_dev *dev, struct irq_data *irqd)
> +/* NB: during map, hv_interrupt_entry is saved via data->chip_data */
> +static void hv_teardown_msi_irq(struct pci_dev *pdev, struct irq_data *irqd)
>  {
> -	struct hv_interrupt_entry old_entry;
> +	struct hv_interrupt_entry irq_entry;
>  	struct msi_msg msg;
>  
>  	if (!irqd->chip_data) {
> @@ -281,13 +286,13 @@ static void hv_teardown_msi_irq(struct pci_dev *dev, struct irq_data *irqd)
>  		return;
>  	}
>  
> -	old_entry = *(struct hv_interrupt_entry *)irqd->chip_data;
> -	entry_to_msi_msg(&old_entry, &msg);
> +	irq_entry = *(struct hv_interrupt_entry *)irqd->chip_data;
> +	entry_to_msi_msg(&irq_entry, &msg);
>  
>  	kfree(irqd->chip_data);
>  	irqd->chip_data = NULL;
>  
> -	(void)hv_unmap_msi_interrupt(dev, &old_entry);
> +	(void)hv_unmap_msi_interrupt(pdev, &irq_entry);
>  }
>  
>  /*
> @@ -302,7 +307,8 @@ static struct irq_chip hv_pci_msi_controller = {
>  };
>  
>  static bool hv_init_dev_msi_info(struct device *dev, struct irq_domain *domain,
> -				 struct irq_domain *real_parent, struct msi_domain_info *info)
> +				 struct irq_domain *real_parent,
> +				 struct msi_domain_info *info)
>  {
>  	struct irq_chip *chip = info->chip;
>  
> @@ -317,7 +323,8 @@ static bool hv_init_dev_msi_info(struct device *dev, struct irq_domain *domain,
>  }
>  
>  #define HV_MSI_FLAGS_SUPPORTED	(MSI_GENERIC_FLAGS_MASK | MSI_FLAG_PCI_MSIX)
> -#define HV_MSI_FLAGS_REQUIRED	(MSI_FLAG_USE_DEF_DOM_OPS | MSI_FLAG_USE_DEF_CHIP_OPS)
> +#define HV_MSI_FLAGS_REQUIRED	(MSI_FLAG_USE_DEF_DOM_OPS |	\
> +				 MSI_FLAG_USE_DEF_CHIP_OPS)
>  
>  static struct msi_parent_ops hv_msi_parent_ops = {
>  	.supported_flags	= HV_MSI_FLAGS_SUPPORTED,
> @@ -329,14 +336,14 @@ static struct msi_parent_ops hv_msi_parent_ops = {
>  	.init_dev_msi_info	= hv_init_dev_msi_info,
>  };
>  
> -static int hv_msi_domain_alloc(struct irq_domain *d, unsigned int virq, unsigned int nr_irqs,
> -			       void *arg)
> +/* Allocate nr_irqs IRQs for the given irq domain */
> +static int hv_msi_domain_alloc(struct irq_domain *d, unsigned int virq,
> +			       unsigned int nr_irqs, void *arg)
>  {
>  	/*
> -	 * TODO: The allocation bits of hv_irq_compose_msi_msg(), i.e. everything except
> -	 * entry_to_msi_msg() should be in here.
> +	 * TODO: The allocation bits of hv_irq_compose_msi_msg(), i.e.
> +	 *	 everything except entry_to_msi_msg() should be in here.
>  	 */
> -
>  	int ret;
>  
>  	ret = irq_domain_alloc_irqs_parent(d, virq, nr_irqs, arg);
> @@ -344,13 +351,15 @@ static int hv_msi_domain_alloc(struct irq_domain *d, unsigned int virq, unsigned
>  		return ret;
>  
>  	for (int i = 0; i < nr_irqs; ++i) {
> -		irq_domain_set_info(d, virq + i, 0, &hv_pci_msi_controller, NULL,
> -				    handle_edge_irq, NULL, "edge");
> +		irq_domain_set_info(d, virq + i, 0, &hv_pci_msi_controller,
> +				    NULL, handle_edge_irq, NULL, "edge");
>  	}
> +
>  	return 0;
>  }
>  
> -static void hv_msi_domain_free(struct irq_domain *d, unsigned int virq, unsigned int nr_irqs)
> +static void hv_msi_domain_free(struct irq_domain *d, unsigned int virq,
> +			       unsigned int nr_irqs)
>  {
>  	for (int i = 0; i < nr_irqs; ++i) {
>  		struct irq_data *irqd = irq_domain_get_irq_data(d, virq);
> @@ -362,6 +371,7 @@ static void hv_msi_domain_free(struct irq_domain *d, unsigned int virq, unsigned
>  
>  		hv_teardown_msi_irq(to_pci_dev(desc->dev), irqd);
>  	}
> +
>  	irq_domain_free_irqs_top(d, virq, nr_irqs);
>  }
>  
> @@ -394,25 +404,25 @@ struct irq_domain * __init hv_create_pci_msi_domain(void)
>  
>  int hv_unmap_ioapic_interrupt(int ioapic_id, struct hv_interrupt_entry *entry)
>  {
> -	union hv_device_id device_id;
> +	union hv_device_id hv_devid;
>  
> -	device_id.as_uint64 = 0;
> -	device_id.device_type = HV_DEVICE_TYPE_IOAPIC;
> -	device_id.ioapic.ioapic_id = (u8)ioapic_id;
> +	hv_devid.as_uint64 = 0;
> +	hv_devid.device_type = HV_DEVICE_TYPE_IOAPIC;
> +	hv_devid.ioapic.ioapic_id = (u8)ioapic_id;
>  
> -	return hv_unmap_interrupt(device_id.as_uint64, entry);
> +	return hv_unmap_interrupt(hv_devid.as_uint64, entry);
>  }
>  EXPORT_SYMBOL_GPL(hv_unmap_ioapic_interrupt);
>  
>  int hv_map_ioapic_interrupt(int ioapic_id, bool level, int cpu, int vector,
>  		struct hv_interrupt_entry *entry)
>  {
> -	union hv_device_id device_id;
> +	union hv_device_id hv_devid;
>  
> -	device_id.as_uint64 = 0;
> -	device_id.device_type = HV_DEVICE_TYPE_IOAPIC;
> -	device_id.ioapic.ioapic_id = (u8)ioapic_id;
> +	hv_devid.as_uint64 = 0;
> +	hv_devid.device_type = HV_DEVICE_TYPE_IOAPIC;
> +	hv_devid.ioapic.ioapic_id = (u8)ioapic_id;
>  
> -	return hv_map_interrupt(device_id, level, cpu, vector, entry);
> +	return hv_map_interrupt(hv_devid, level, cpu, vector, entry);
>  }
>  EXPORT_SYMBOL_GPL(hv_map_ioapic_interrupt);
> -- 
> 2.51.2.vfs.0.1
> 

Re: [PATCH V3 02/11] x86/hyperv: Cosmetic changes in irqdomain.c for readability

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider:
- [High] Resource leak in `hv_msi_domain_free()` when freeing multiple IRQs.
- [High] Uninitialized memory write to hardware MSI registers in `hv_irq_compose_msi_msg()` error paths.
- [High] Invalid hardware state read in `hv_build_devid_type_pci()` for Type 0 PCI-X leaf devices.
--

commit 8c84576bf69ec6b4d58407408095bf71a9940bf2
Author: Mukesh R <mrathor@linux.microsoft.com>

x86/hyperv: Cosmetic changes in irqdomain.c for readability

Make cosmetic changes such as renaming variables for consistency, fixing
checkpatch warnings, updating indentation, and replacing spaces with tabs.

> diff --git a/arch/x86/hyperv/irqdomain.c b/arch/x86/hyperv/irqdomain.c
> --- a/arch/x86/hyperv/irqdomain.c
> +++ b/arch/x86/hyperv/irqdomain.c
[ ... ]
> @@ -115,67 +112,71 @@ static int get_rid_cb(struct pci_dev *pdev, u16 alias, void *data)
>  	return 0;
>  }
>  
> -static union hv_device_id hv_build_pci_dev_id(struct pci_dev *dev)
> +static union hv_device_id hv_build_devid_type_pci(struct pci_dev *pdev)
>  {
[ ... ]
> -	if (data.bridge) {
> -		int pos;
> +	if (data.bridge == NULL)
> +		goto out;
>  
> -		/*
> -		 * Microsoft Hypervisor requires a bus range when the bridge is
> -		 * running in PCI-X mode.
[ ... ]
> -		pos = pci_find_capability(data.bridge, PCI_CAP_ID_PCIX);
> -		if (pos) {
> -			u16 status;
> +	pos = pci_find_capability(data.bridge, PCI_CAP_ID_PCIX);
> +	if (pos) {
> +		u16 status;

If the leaf device is on the root bus, data.bridge will point to the leaf
device itself (a Type 0 device) after pci_for_each_dma_alias() completes.
Does this code incorrectly assume data.bridge is always a Type 1 bridge?

If it evaluates a Type 0 device here, reading PCI_X_BRIDGE_SSTATUS aliases
the Type 0 Command register. This could cause the code to read standard
Type 1 PCI_SECONDARY_BUS and PCI_SUBORDINATE_BUS offsets (which fall into
the middle of BAR2 for a Type 0 device), sending arbitrary BAR values as
shadow bus ranges to the hypervisor.

[ ... ]
> @@ -249,10 +253,8 @@ static void hv_irq_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
>  	}
>  
>  	stored_entry = kzalloc_obj(*stored_entry, GFP_ATOMIC);
> -	if (!stored_entry) {
> -		pr_debug("%s: failed to allocate chip data\n", __func__);
> +	if (!stored_entry)
>  		return;
> -	}

If kzalloc_obj() or hv_map_msi_interrupt() fails, this returns early
without populating the struct msi_msg *msg parameter.

Since callers (like msi_domain_activate() or irq_chip_compose_msi_msg())
allocate msg on the stack and cannot check for errors due to the void
return type, does this result in uninitialized stack memory being blindly
written to the hardware MSI registers?

[ ... ]
> @@ -344,13 +351,15 @@ static int hv_msi_domain_alloc(struct irq_domain *d, unsigned int virq, unsigned
>  		return ret;
>  
>  	for (int i = 0; i < nr_irqs; ++i) {
> -		irq_domain_set_info(d, virq + i, 0, &hv_pci_msi_controller, NULL,
> -				    handle_edge_irq, NULL, "edge");
> +		irq_domain_set_info(d, virq + i, 0, &hv_pci_msi_controller,
> +				    NULL, handle_edge_irq, NULL, "edge");
>  	}
> +
>  	return 0;
>  }
>  
> -static void hv_msi_domain_free(struct irq_domain *d, unsigned int virq, unsigned int nr_irqs)
> +static void hv_msi_domain_free(struct irq_domain *d, unsigned int virq,
> +			       unsigned int nr_irqs)
>  {
>  	for (int i = 0; i < nr_irqs; ++i) {
>  		struct irq_data *irqd = irq_domain_get_irq_data(d, virq);

Does this loop leak chip_data and leave IRQs mapped in the hypervisor for
the remaining nr_irqs - 1 IRQs?

It appears to call irq_domain_get_irq_data() using the base virq on every
iteration instead of virq + i, causing hv_teardown_msi_irq() to be
repeatedly invoked on the first IRQ only.

> @@ -362,6 +371,7 @@ static void hv_msi_domain_free(struct irq_domain *d, unsigned int virq, unsigned
>  
>  		hv_teardown_msi_irq(to_pci_dev(desc->dev), irqd);
>  	}
> +
>  	irq_domain_free_irqs_top(d, virq, nr_irqs);
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260512020259.1678627-1-mrathor@linux.microsoft.com?part=2

[PATCH V3 03/11] mshv: Provide a way to get partition ID if running in a VMM process

[Mukesh R]

Many PCI passthru related hypercalls require partition ID of the target
guest. Guests are actually managed by MSHV driver and the partition ID
is only maintained there. Add a field in the partition struct in MSHV
driver to save the tgid of the VMM process creating the partition, and
add a function there to retrieve partition ID if the current process is
a VMM process.

Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
---
 drivers/hv/mshv_root.h         |  1 +
 drivers/hv/mshv_root_main.c    | 22 ++++++++++++++++++++++
 include/asm-generic/mshyperv.h |  5 +++++
 3 files changed, 28 insertions(+)

diff --git a/drivers/hv/mshv_root.h b/drivers/hv/mshv_root.h
index 1f086dcb7aa1..a85c24dcc701 100644
--- a/drivers/hv/mshv_root.h
+++ b/drivers/hv/mshv_root.h
@@ -138,6 +138,7 @@ struct mshv_partition {
 
 	struct mshv_girq_routing_table __rcu *pt_girq_tbl;
 	u64 isolation_type;
+	pid_t pt_vmm_tgid;
 	bool import_completed;
 	bool pt_initialized;
 #if IS_ENABLED(CONFIG_DEBUG_FS)
diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
index bd1359eb58dd..02c107458be9 100644
--- a/drivers/hv/mshv_root_main.c
+++ b/drivers/hv/mshv_root_main.c
@@ -1908,6 +1908,27 @@ mshv_partition_release(struct inode *inode, struct file *filp)
 	return 0;
 }
 
+/* Given a process tgid, return partition id if it is a VMM process */
+u64 mshv_current_partid(void)
+{
+	struct mshv_partition *pt;
+	int i;
+	u64 ret_ptid = HV_PARTITION_ID_INVALID;
+
+	rcu_read_lock();
+
+	hash_for_each_rcu(mshv_root.pt_htable, i, pt, pt_hnode) {
+		if (pt->pt_vmm_tgid == current->tgid) {
+			ret_ptid = pt->pt_id;
+			break;
+		}
+	}
+
+	rcu_read_unlock();
+	return ret_ptid;
+}
+EXPORT_SYMBOL_GPL(mshv_current_partid);
+
 static int
 add_partition(struct mshv_partition *partition)
 {
@@ -2073,6 +2094,7 @@ mshv_ioctl_create_partition(void __user *user_arg, struct device *module_dev)
 		goto cleanup_irq_srcu;
 
 	partition->pt_id = pt_id;
+	partition->pt_vmm_tgid = current->tgid;
 
 	ret = add_partition(partition);
 	if (ret)
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index bf601d67cecb..e8cbc4e3f7ad 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -350,6 +350,7 @@ int hv_call_add_logical_proc(int node, u32 lp_index, u32 acpi_id);
 int hv_call_notify_all_processors_started(void);
 bool hv_lp_exists(u32 lp_index);
 int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u32 flags);
+u64 mshv_current_partid(void);
 
 #else /* CONFIG_MSHV_ROOT */
 static inline bool hv_root_partition(void) { return false; }
@@ -380,6 +381,10 @@ static inline int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u3
 {
 	return -EOPNOTSUPP;
 }
+static inline u64 mshv_current_partid(void)
+{
+	return HV_PARTITION_ID_INVALID;
+}
 #endif /* CONFIG_MSHV_ROOT */
 
 static inline int hv_deposit_memory(u64 partition_id, u64 status)
-- 
2.51.2.vfs.0.1

Re: [PATCH V3 03/11] mshv: Provide a way to get partition ID if running in a VMM process

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider:
- [High] Tying VM partition IDs to process TGIDs (`current->tgid`) is an architectural flaw causing isolation breakage and security risks.
- [High] `mshv_current_partid()` returns a raw partition ID without taking a reference, creating a TOCTOU vulnerability.
- [High] Pre-existing Use-After-Free in `destroy_partition()` due to RCU-001 violation during VP teardown.
--

commit 528e38745b2ae16c0fd8ad4876d893d1b1fea027
Author: Mukesh R <mrathor@linux.microsoft.com>

mshv: Provide a way to get partition ID if running in a VMM process

This commit introduces mshv_current_partid() to allow retrieving the
partition id for the current vmm process. It adds a pt_vmm_tgid field
to the mshv_partition struct and sets it during partition creation.
The partition id is found by iterating the global hash table.

> diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
> index bd1359eb58dd4..02c107458be90 100644
> --- a/drivers/hv/mshv_root_main.c
> +++ b/drivers/hv/mshv_root_main.c
> @@ -1908,6 +1908,27 @@ mshv_partition_release(struct inode *inode, struct file *filp)
>  	return 0;
>  }
>  
> +/* Given a process tgid, return partition id if it is a VMM process */
> +u64 mshv_current_partid(void)
> +{
> +	struct mshv_partition *pt;
> +	int i;
> +	u64 ret_ptid = HV_PARTITION_ID_INVALID;
> +
> +	rcu_read_lock();
> +
> +	hash_for_each_rcu(mshv_root.pt_htable, i, pt, pt_hnode) {
> +		if (pt->pt_vmm_tgid == current->tgid) {

Is tying the partition id to the process tgid safe?

Since a single vmm process can create multiple partitions, this loop returns
the first partition matching the tgid. This could result in pci passthrough
operations being misrouted to the wrong partition if a process manages
multiple virtual machines.

Also, since the partition's lifecycle is tied to an anonymous file descriptor,
passing the fd to another process and exiting would break
mshv_current_partid() for the new process.

Additionally, if the operating system recycles the old tgid, an unrelated
process might gain access to the partition id.

Should explicit file descriptor tracking be used instead of global process
ids?

> +			ret_ptid = pt->pt_id;
> +			break;
> +		}
> +	}
> +
> +	rcu_read_unlock();
> +	return ret_ptid;

Does returning a raw partition id without taking a reference create a race
condition?

After rcu_read_unlock() is called and the pt_id is returned, a concurrent
thread in the vmm could close the partition's file descriptor, causing the
partition to be deleted in the hypervisor.

If the hypervisor recycles the pt_id for a newly created partition belonging
to a completely different process, the pending iommu attachment or pci
passthrough hypercall will use the stale pt_id.

Can this allow the vmm to inadvertently attach its devices to an unrelated
partition?

> +}

This isn't a regression in this patch, but looking at the partition lifecycle
code, does destroy_partition() have a use-after-free?

destroy_partition() frees the virtual processor structures (kfree(vp))
before calling remove_partition(partition), which removes the partition
from the rcu-protected global hash table (pt_htable) and calls
synchronize_rcu().

Because the partition remains visible to rcu readers during the teardown loop,
can an interrupt handler (e.g., in mshv_synic.c) call mshv_partition_find(),
successfully retrieve the partition, and read
vp = partition->pt_vp_array[vp_index]?

If this happens concurrently with or immediately after kfree(vp), the
interrupt handler would access freed memory.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260512020259.1678627-1-mrathor@linux.microsoft.com?part=3

[PATCH V3 04/11] mshv: Declarations and definitions for VFIO-MSHV bridge device

[Mukesh R]

Add data structs needed by the subsequent patch that introduces a new
module to implement VFIO-MSHV pseudo device.

Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
---
 drivers/hv/mshv_root.h    | 19 +++++++++++++++++++
 include/uapi/linux/mshv.h | 30 ++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+)

diff --git a/drivers/hv/mshv_root.h b/drivers/hv/mshv_root.h
index a85c24dcc701..b9880d0bdc4d 100644
--- a/drivers/hv/mshv_root.h
+++ b/drivers/hv/mshv_root.h
@@ -227,6 +227,25 @@ struct port_table_info {
 	};
 };
 
+struct mshv_device {
+	const struct mshv_device_ops *device_ops;
+	struct mshv_partition *device_pt;
+	void *device_private;
+	struct hlist_node device_ptnode;
+};
+
+struct mshv_device_ops {
+	const char *device_name;
+	long (*device_create)(struct mshv_device *dev);
+	void (*device_release)(struct mshv_device *dev);
+	long (*device_set_attr)(struct mshv_device *dev,
+				struct mshv_device_attr *attr);
+	long (*device_has_attr)(struct mshv_device *dev,
+				struct mshv_device_attr *attr);
+};
+
+extern struct mshv_device_ops mshv_vfio_device_ops;
+
 int mshv_update_routing_table(struct mshv_partition *partition,
 			      const struct mshv_user_irq_entry *entries,
 			      unsigned int numents);
diff --git a/include/uapi/linux/mshv.h b/include/uapi/linux/mshv.h
index 32ff92b6342b..be6fe3ee8707 100644
--- a/include/uapi/linux/mshv.h
+++ b/include/uapi/linux/mshv.h
@@ -404,4 +404,34 @@ struct mshv_sint_mask {
 /* hv_hvcall device */
 #define MSHV_HVCALL_SETUP        _IOW(MSHV_IOCTL, 0x1E, struct mshv_vtl_hvcall_setup)
 #define MSHV_HVCALL              _IOWR(MSHV_IOCTL, 0x1F, struct mshv_vtl_hvcall)
+
+/* Device passhthru */
+#define MSHV_CREATE_DEVICE_TEST		1
+
+enum {
+	MSHV_DEV_TYPE_VFIO,
+	MSHV_DEV_TYPE_MAX,
+};
+
+struct mshv_create_device {
+	__u32	type;	     /* in: MSHV_DEV_TYPE_xxx */
+	__u32	fd;	     /* out: device handle */
+	__u32	flags;	     /* in: MSHV_CREATE_DEVICE_xxx */
+};
+
+#define MSHV_DEV_VFIO_FILE      1
+#define MSHV_DEV_VFIO_FILE_ADD	1
+#define MSHV_DEV_VFIO_FILE_DEL	2
+
+struct mshv_device_attr {
+	__u32	flags;		/* no flags currently defined */
+	__u32	group;		/* device-defined */
+	__u64	attr;		/* group-defined */
+	__u64	addr;		/* userspace address of attr data */
+};
+
+/* Device fds created with MSHV_CREATE_DEVICE */
+#define MSHV_SET_DEVICE_ATTR	_IOW(MSHV_IOCTL, 0x00, struct mshv_device_attr)
+#define MSHV_HAS_DEVICE_ATTR	_IOW(MSHV_IOCTL, 0x01, struct mshv_device_attr)
+
 #endif
-- 
2.51.2.vfs.0.1

Re: [PATCH V3 04/11] mshv: Declarations and definitions for VFIO-MSHV bridge device

[Souradeep Chakrabarti]

On Mon, May 11, 2026 at 07:02:52PM -0700, Mukesh R wrote:
> Add data structs needed by the subsequent patch that introduces a new
> module to implement VFIO-MSHV pseudo device.
> 
Reviewed-by: Souradeep Chakrabarti <schakrabarti@linux.microsoft.com>
> Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
> ---
>  drivers/hv/mshv_root.h    | 19 +++++++++++++++++++
>  include/uapi/linux/mshv.h | 30 ++++++++++++++++++++++++++++++
>  2 files changed, 49 insertions(+)
> 
> diff --git a/drivers/hv/mshv_root.h b/drivers/hv/mshv_root.h
> index a85c24dcc701..b9880d0bdc4d 100644
> --- a/drivers/hv/mshv_root.h
> +++ b/drivers/hv/mshv_root.h
> @@ -227,6 +227,25 @@ struct port_table_info {
>  	};
>  };
>  
> +struct mshv_device {
> +	const struct mshv_device_ops *device_ops;
> +	struct mshv_partition *device_pt;
> +	void *device_private;
> +	struct hlist_node device_ptnode;
> +};
> +
> +struct mshv_device_ops {
> +	const char *device_name;
> +	long (*device_create)(struct mshv_device *dev);
> +	void (*device_release)(struct mshv_device *dev);
> +	long (*device_set_attr)(struct mshv_device *dev,
> +				struct mshv_device_attr *attr);
> +	long (*device_has_attr)(struct mshv_device *dev,
> +				struct mshv_device_attr *attr);
> +};
> +
> +extern struct mshv_device_ops mshv_vfio_device_ops;
> +
>  int mshv_update_routing_table(struct mshv_partition *partition,
>  			      const struct mshv_user_irq_entry *entries,
>  			      unsigned int numents);
> diff --git a/include/uapi/linux/mshv.h b/include/uapi/linux/mshv.h
> index 32ff92b6342b..be6fe3ee8707 100644
> --- a/include/uapi/linux/mshv.h
> +++ b/include/uapi/linux/mshv.h
> @@ -404,4 +404,34 @@ struct mshv_sint_mask {
>  /* hv_hvcall device */
>  #define MSHV_HVCALL_SETUP        _IOW(MSHV_IOCTL, 0x1E, struct mshv_vtl_hvcall_setup)
>  #define MSHV_HVCALL              _IOWR(MSHV_IOCTL, 0x1F, struct mshv_vtl_hvcall)
> +
> +/* Device passhthru */
> +#define MSHV_CREATE_DEVICE_TEST		1
> +
> +enum {
> +	MSHV_DEV_TYPE_VFIO,
> +	MSHV_DEV_TYPE_MAX,
> +};
> +
> +struct mshv_create_device {
> +	__u32	type;	     /* in: MSHV_DEV_TYPE_xxx */
> +	__u32	fd;	     /* out: device handle */
> +	__u32	flags;	     /* in: MSHV_CREATE_DEVICE_xxx */
> +};
> +
> +#define MSHV_DEV_VFIO_FILE      1
> +#define MSHV_DEV_VFIO_FILE_ADD	1
> +#define MSHV_DEV_VFIO_FILE_DEL	2
> +
> +struct mshv_device_attr {
> +	__u32	flags;		/* no flags currently defined */
> +	__u32	group;		/* device-defined */
> +	__u64	attr;		/* group-defined */
> +	__u64	addr;		/* userspace address of attr data */
> +};
> +
> +/* Device fds created with MSHV_CREATE_DEVICE */
> +#define MSHV_SET_DEVICE_ATTR	_IOW(MSHV_IOCTL, 0x00, struct mshv_device_attr)
> +#define MSHV_HAS_DEVICE_ATTR	_IOW(MSHV_IOCTL, 0x01, struct mshv_device_attr)
> +
>  #endif
> -- 
> 2.51.2.vfs.0.1
> 

[PATCH V3 05/11] mshv: Implement mshv bridge device for VFIO

[Mukesh R]

Add a new file to implement VFIO-MSHV bridge pseudo device. These
functions are called in the VFIO framework, and credits to kvm/vfio.c
as this file was adapted from it.

Co-developed-by: Wei Liu <wei.liu@kernel.org>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
---
 drivers/hv/Makefile       |   3 +-
 drivers/hv/mshv_vfio.c    | 211 ++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/mshv.h |   1 +
 3 files changed, 214 insertions(+), 1 deletion(-)
 create mode 100644 drivers/hv/mshv_vfio.c

diff --git a/drivers/hv/Makefile b/drivers/hv/Makefile
index 888a748cc7cb..9ab6fc254c38 100644
--- a/drivers/hv/Makefile
+++ b/drivers/hv/Makefile
@@ -14,7 +14,8 @@ hv_vmbus-y := vmbus_drv.o \
 hv_vmbus-$(CONFIG_HYPERV_TESTING)	+= hv_debugfs.o
 hv_utils-y := hv_util.o hv_kvp.o hv_snapshot.o hv_utils_transport.o
 mshv_root-y := mshv_root_main.o mshv_synic.o mshv_eventfd.o mshv_irq.o \
-	       mshv_root_hv_call.o mshv_portid_table.o mshv_regions.o
+	       mshv_root_hv_call.o mshv_portid_table.o mshv_regions.o  \
+               mshv_vfio.o
 mshv_root-$(CONFIG_DEBUG_FS) += mshv_debugfs.o
 mshv_root-$(CONFIG_TRACEPOINTS) += mshv_trace.o
 mshv_vtl-y := mshv_vtl_main.o
diff --git a/drivers/hv/mshv_vfio.c b/drivers/hv/mshv_vfio.c
new file mode 100644
index 000000000000..00a97920e25b
--- /dev/null
+++ b/drivers/hv/mshv_vfio.c
@@ -0,0 +1,211 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * VFIO-MSHV bridge pseudo device
+ *
+ * Heavily inspired by the VFIO-KVM bridge pseudo device.
+ */
+#include <linux/errno.h>
+#include <linux/file.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/vfio.h>
+#include <asm/mshyperv.h>
+
+#include "mshv.h"
+#include "mshv_root.h"
+
+struct mshv_vfio_file {
+	struct list_head node;
+	struct file *file;	/* list of struct mshv_vfio_file */
+};
+
+struct mshv_vfio {
+	struct list_head file_list;
+	struct mutex lock;
+};
+
+static bool mshv_vfio_file_is_valid(struct file *file)
+{
+	bool (*fn)(struct file *file);
+	bool ret;
+
+	fn = symbol_get(vfio_file_is_valid);
+	if (!fn)
+		return false;
+
+	ret = fn(file);
+
+	symbol_put(vfio_file_is_valid);
+
+	return ret;
+}
+
+static long mshv_vfio_file_add(struct mshv_device *mshvdev, unsigned int fd)
+{
+	struct mshv_vfio *mshv_vfio = mshvdev->device_private;
+	struct mshv_vfio_file *mvf;
+	struct file *filp;
+	long ret = 0;
+
+	filp = fget(fd);
+	if (!filp)
+		return -EBADF;
+
+	/* Ensure the FD is a vfio FD. */
+	if (!mshv_vfio_file_is_valid(filp)) {
+		ret = -EINVAL;
+		goto out_fput;
+	}
+
+	mutex_lock(&mshv_vfio->lock);
+
+	list_for_each_entry(mvf, &mshv_vfio->file_list, node) {
+		if (mvf->file == filp) {
+			ret = -EEXIST;
+			goto out_unlock;
+		}
+	}
+
+	mvf = kzalloc(sizeof(*mvf), GFP_KERNEL_ACCOUNT);
+	if (!mvf) {
+		ret = -ENOMEM;
+		goto out_unlock;
+	}
+
+	mvf->file = get_file(filp);
+	list_add_tail(&mvf->node, &mshv_vfio->file_list);
+
+out_unlock:
+	mutex_unlock(&mshv_vfio->lock);
+out_fput:
+	fput(filp);
+	return ret;
+}
+
+static long mshv_vfio_file_del(struct mshv_device *mshvdev, unsigned int fd)
+{
+	struct mshv_vfio *mshv_vfio = mshvdev->device_private;
+	struct mshv_vfio_file *mvf;
+	long ret;
+
+	CLASS(fd, f)(fd);
+
+	if (fd_empty(f))
+		return -EBADF;
+
+	ret = -ENOENT;
+	mutex_lock(&mshv_vfio->lock);
+
+	list_for_each_entry(mvf, &mshv_vfio->file_list, node) {
+		if (mvf->file != fd_file(f))
+			continue;
+
+		list_del(&mvf->node);
+		fput(mvf->file);
+		kfree(mvf);
+		ret = 0;
+		break;
+	}
+
+	mutex_unlock(&mshv_vfio->lock);
+	return ret;
+}
+
+static long mshv_vfio_set_file(struct mshv_device *mshvdev, long attr,
+			      void __user *arg)
+{
+	int32_t __user *argp = arg;
+	int32_t fd;
+
+	switch (attr) {
+	case MSHV_DEV_VFIO_FILE_ADD:
+		if (get_user(fd, argp))
+			return -EFAULT;
+		return mshv_vfio_file_add(mshvdev, fd);
+
+	case MSHV_DEV_VFIO_FILE_DEL:
+		if (get_user(fd, argp))
+			return -EFAULT;
+		return mshv_vfio_file_del(mshvdev, fd);
+	}
+
+	return -ENXIO;
+}
+
+static long mshv_vfio_set_attr(struct mshv_device *mshvdev,
+			      struct mshv_device_attr *attr)
+{
+	switch (attr->group) {
+	case MSHV_DEV_VFIO_FILE:
+		return mshv_vfio_set_file(mshvdev, attr->attr,
+					  u64_to_user_ptr(attr->addr));
+	}
+
+	return -ENXIO;
+}
+
+static long mshv_vfio_has_attr(struct mshv_device *mshvdev,
+			      struct mshv_device_attr *attr)
+{
+	switch (attr->group) {
+	case MSHV_DEV_VFIO_FILE:
+		switch (attr->attr) {
+		case MSHV_DEV_VFIO_FILE_ADD:
+		case MSHV_DEV_VFIO_FILE_DEL:
+			return 0;
+		}
+
+		break;
+	}
+
+	return -ENXIO;
+}
+
+static long mshv_vfio_create_device(struct mshv_device *mshvdev)
+{
+	struct mshv_device *tmp;
+	struct mshv_vfio *mshv_vfio;
+
+	/* Only one VFIO "device" per VM */
+	hlist_for_each_entry(tmp, &mshvdev->device_pt->pt_devices,
+			     device_ptnode)
+		if (tmp->device_ops == &mshv_vfio_device_ops)
+			return -EBUSY;
+
+	mshv_vfio = kzalloc(sizeof(*mshv_vfio), GFP_KERNEL_ACCOUNT);
+	if (mshv_vfio == NULL)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&mshv_vfio->file_list);
+	mutex_init(&mshv_vfio->lock);
+
+	mshvdev->device_private = mshv_vfio;
+
+	return 0;
+}
+
+/* This is called from mshv_device_fop_release() */
+static void mshv_vfio_release_device(struct mshv_device *mshvdev)
+{
+	struct mshv_vfio *mv = mshvdev->device_private;
+	struct mshv_vfio_file *mvf, *tmp;
+
+	list_for_each_entry_safe(mvf, tmp, &mv->file_list, node) {
+		fput(mvf->file);
+		list_del(&mvf->node);
+		kfree(mvf);
+	}
+
+	kfree(mv);
+	kfree(mshvdev);
+}
+
+struct mshv_device_ops mshv_vfio_device_ops = {
+	.device_name = "mshv-vfio",
+	.device_create = mshv_vfio_create_device,
+	.device_release = mshv_vfio_release_device,
+	.device_set_attr = mshv_vfio_set_attr,
+	.device_has_attr = mshv_vfio_has_attr,
+};
diff --git a/include/uapi/linux/mshv.h b/include/uapi/linux/mshv.h
index be6fe3ee8707..b038a79786d2 100644
--- a/include/uapi/linux/mshv.h
+++ b/include/uapi/linux/mshv.h
@@ -254,6 +254,7 @@ struct mshv_root_hvcall {
 #define MSHV_GET_GPAP_ACCESS_BITMAP	_IOWR(MSHV_IOCTL, 0x06, struct mshv_gpap_access_bitmap)
 /* Generic hypercall */
 #define MSHV_ROOT_HVCALL		_IOWR(MSHV_IOCTL, 0x07, struct mshv_root_hvcall)
+#define MSHV_CREATE_DEVICE             _IOWR(MSHV_IOCTL, 0x08, struct mshv_create_device)
 
 /*
  ********************************
-- 
2.51.2.vfs.0.1

Re: [PATCH V3 05/11] mshv: Implement mshv bridge device for VFIO

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [High] Unprotected access to `pt_devices` list and missing lockdep assertion.
- [Low] The `mshv_vfio_device_ops` structure is missing the `const` qualifier.
--

commit 96ab470ecc51b095ed8b1538e4abdf37d030b039
Author: Mukesh R <mrathor@linux.microsoft.com>
Subject: mshv: Implement mshv bridge device for VFIO

This commit introduces a new VFIO-MSHV bridge pseudo device file, adapted
from KVM's VFIO bridge. It provides the necessary device operations to link
VFIO files with an MSHV partition.

> diff --git a/drivers/hv/mshv_vfio.c b/drivers/hv/mshv_vfio.c
> new file mode 100644
> index 0000000000000..00a97920e25ba
> --- /dev/null
> +++ b/drivers/hv/mshv_vfio.c
[ ... ]
> +static long mshv_vfio_create_device(struct mshv_device *mshvdev)
> +{
> +	struct mshv_device *tmp;
> +	struct mshv_vfio *mshv_vfio;
> +
> +	/* Only one VFIO "device" per VM */
> +	hlist_for_each_entry(tmp, &mshvdev->device_pt->pt_devices,
> +			     device_ptnode)
> +		if (tmp->device_ops == &mshv_vfio_device_ops)
> +			return -EBUSY;

Are we missing a lockdep assertion here to ensure the partition lock is held?

Since this iterates over the pt_devices list to enforce a singleton device,
could concurrent ioctl calls bypass this check and corrupt the hlist if the
caller doesn't acquire the lock?

[ ... ]

> +struct mshv_device_ops mshv_vfio_device_ops = {
> +	.device_name = "mshv-vfio",
> +	.device_create = mshv_vfio_create_device,
> +	.device_release = mshv_vfio_release_device,
> +	.device_set_attr = mshv_vfio_set_attr,
> +	.device_has_attr = mshv_vfio_has_attr,
> +};

Should mshv_vfio_device_ops be declared as const?

The structure consists entirely of function pointers and is never modified
after initialization. Making it const would place it in read-only memory.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260512020259.1678627-1-mrathor@linux.microsoft.com?part=5

[PATCH V3 06/11] mshv: Add ioctl support for MSHV-VFIO bridge device

[Mukesh R]

Add ioctl support for creating MSHV devices for a partition. At
present only VFIO device types are supported, but more could be
added. At a high level, a partition ioctl to create device verifies
it is of type VFIO and does some setup for bridge code in mshv_vfio.c.
Adapted from KVM device ioctls.

Co-developed-by: Wei Liu <wei.liu@kernel.org>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
---
 drivers/hv/mshv_root_main.c | 116 ++++++++++++++++++++++++++++++++++++
 1 file changed, 116 insertions(+)

diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
index 02c107458be9..6ceb5f608589 100644
--- a/drivers/hv/mshv_root_main.c
+++ b/drivers/hv/mshv_root_main.c
@@ -1625,6 +1625,119 @@ mshv_partition_ioctl_initialize(struct mshv_partition *partition)
 	return ret;
 }
 
+static long mshv_device_attr_ioctl(struct mshv_device *mshv_dev, int cmd,
+				   ulong uarg)
+{
+	struct mshv_device_attr attr;
+	const struct mshv_device_ops *devops = mshv_dev->device_ops;
+
+	if (copy_from_user(&attr, (void __user *)uarg, sizeof(attr)))
+		return -EFAULT;
+
+	switch (cmd) {
+	case MSHV_SET_DEVICE_ATTR:
+		if (devops->device_set_attr)
+			return devops->device_set_attr(mshv_dev, &attr);
+		break;
+	case MSHV_HAS_DEVICE_ATTR:
+		if (devops->device_has_attr)
+			return devops->device_has_attr(mshv_dev, &attr);
+		break;
+	}
+
+	return -EPERM;
+}
+
+static long mshv_device_fop_ioctl(struct file *filp, unsigned int cmd,
+				  ulong uarg)
+{
+	struct mshv_device *mshv_dev = filp->private_data;
+
+	switch (cmd) {
+	case MSHV_SET_DEVICE_ATTR:
+	case MSHV_HAS_DEVICE_ATTR:
+		return mshv_device_attr_ioctl(mshv_dev, cmd, uarg);
+	}
+
+	return -ENOTTY;
+}
+
+static int mshv_device_fop_release(struct inode *inode, struct file *filp)
+{
+	struct mshv_device *mshv_dev = filp->private_data;
+	struct mshv_partition *partition = mshv_dev->device_pt;
+
+	if (mshv_dev->device_ops->device_release) {
+		mutex_lock(&partition->pt_mutex);
+		hlist_del(&mshv_dev->device_ptnode);
+		mshv_dev->device_ops->device_release(mshv_dev);
+		mutex_unlock(&partition->pt_mutex);
+	}
+
+	mshv_partition_put(partition);
+	return 0;
+}
+
+static const struct file_operations mshv_device_fops = {
+	.owner = THIS_MODULE,
+	.unlocked_ioctl = mshv_device_fop_ioctl,
+	.release = mshv_device_fop_release,
+};
+
+static long mshv_partition_ioctl_create_device(struct mshv_partition *partition,
+					       void __user *uarg)
+{
+	long rc;
+	struct mshv_create_device devargk;
+	struct mshv_device *mshv_dev;
+	const struct mshv_device_ops *vfio_ops;
+
+	if (copy_from_user(&devargk, uarg, sizeof(devargk)))
+		return -EFAULT;
+
+	/* At present, only VFIO is supported */
+	if (devargk.type != MSHV_DEV_TYPE_VFIO)
+		return -ENODEV;
+
+	if (devargk.flags & MSHV_CREATE_DEVICE_TEST)
+		return 0;
+
+	/* This is freed later by mshv_vfio_release_device() */
+	mshv_dev = kzalloc(sizeof(*mshv_dev), GFP_KERNEL_ACCOUNT);
+	if (mshv_dev == NULL)
+		return -ENOMEM;
+
+	vfio_ops = &mshv_vfio_device_ops;
+	mshv_dev->device_ops = vfio_ops;
+	mshv_dev->device_pt = partition;
+
+	rc = vfio_ops->device_create(mshv_dev);
+	if (rc < 0) {
+		kfree(mshv_dev);
+		return rc;
+	}
+
+	hlist_add_head(&mshv_dev->device_ptnode, &partition->pt_devices);
+
+	mshv_partition_get(partition);
+	rc = anon_inode_getfd(vfio_ops->device_name, &mshv_device_fops,
+			      mshv_dev, O_RDWR | O_CLOEXEC);
+	if (rc < 0)
+		goto undo_out;
+
+	devargk.fd = rc;
+	if (copy_to_user(uarg, &devargk, sizeof(devargk)))
+		return -EFAULT;    /* cleanup in mshv_device_fop_release() */
+
+	return 0;
+
+undo_out:
+	hlist_del(&mshv_dev->device_ptnode);
+	vfio_ops->device_release(mshv_dev);    /* will kfree(mshv_dev) */
+	mshv_partition_put(partition);
+	return rc;
+}
+
 static long
 mshv_partition_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
 {
@@ -1661,6 +1774,9 @@ mshv_partition_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
 	case MSHV_ROOT_HVCALL:
 		ret = mshv_ioctl_passthru_hvcall(partition, true, uarg);
 		break;
+	case MSHV_CREATE_DEVICE:
+		ret = mshv_partition_ioctl_create_device(partition, uarg);
+		break;
 	default:
 		ret = -ENOTTY;
 	}
-- 
2.51.2.vfs.0.1

Re: [PATCH V3 06/11] mshv: Add ioctl support for MSHV-VFIO bridge device

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider:
- [High] FD leak and potential deadlock on copy_to_user() failure after anon_inode_getfd().
- [Medium] Asymmetric memory lifecycle and inconsistent device_release handling.
- [Medium] Missing validation of unknown flags in mshv_partition_ioctl_create_device().
--

commit a0a0db24ca9d194302f458a7afa8a424cc357990
Author: Mukesh R <mrathor@linux.microsoft.com>

mshv: Add ioctl support for MSHV-VFIO bridge device

This commit adds an ioctl for creating MSHV devices for a partition.
Currently only VFIO device types are supported, doing setup for the bridge
code in mshv_vfio.c.

> diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
> index 02c107458be90..6ceb5f608589f 100644
> --- a/drivers/hv/mshv_root_main.c
> +++ b/drivers/hv/mshv_root_main.c

[ ... ]

> @@ -1625,6 +1625,119 @@ mshv_partition_ioctl_initialize(struct mshv_partition *partition)

[ ... ]

> +static int mshv_device_fop_release(struct inode *inode, struct file *filp)
> +{
> +	struct mshv_device *mshv_dev = filp->private_data;
> +	struct mshv_partition *partition = mshv_dev->device_pt;
> +
> +	if (mshv_dev->device_ops->device_release) {
> +		mutex_lock(&partition->pt_mutex);
> +		hlist_del(&mshv_dev->device_ptnode);
> +		mshv_dev->device_ops->device_release(mshv_dev);
> +		mutex_unlock(&partition->pt_mutex);
> +	}

What happens if a future device type does not implement the device_release
callback? It looks like the device would remain indefinitely linked in 
partition->pt_devices while the file descriptor is closed, leading to
list corruption and a memory leak.

Since the device structure is allocated by the core module via kzalloc(),
would it be safer to handle the list removal and generic kfree()
unconditionally in this function?

> +
> +	mshv_partition_put(partition);
> +	return 0;
> +}
> +
> +static const struct file_operations mshv_device_fops = {
> +	.owner = THIS_MODULE,
> +	.unlocked_ioctl = mshv_device_fop_ioctl,
> +	.release = mshv_device_fop_release,
> +};
> +
> +static long mshv_partition_ioctl_create_device(struct mshv_partition *partition,
> +					       void __user *uarg)
> +{
> +	long rc;
> +	struct mshv_create_device devargk;
> +	struct mshv_device *mshv_dev;
> +	const struct mshv_device_ops *vfio_ops;
> +
> +	if (copy_from_user(&devargk, uarg, sizeof(devargk)))
> +		return -EFAULT;
> +
> +	/* At present, only VFIO is supported */
> +	if (devargk.type != MSHV_DEV_TYPE_VFIO)
> +		return -ENODEV;
> +
> +	if (devargk.flags & MSHV_CREATE_DEVICE_TEST)
> +		return 0;

Should we explicitly validate that no undefined flags are set here? 
If a future kernel version introduces new flags for device creation, older 
kernels will silently ignore them and return success instead of -EINVAL, 
breaking forward compatibility.

> +
> +	/* This is freed later by mshv_vfio_release_device() */
> +	mshv_dev = kzalloc(sizeof(*mshv_dev), GFP_KERNEL_ACCOUNT);
> +	if (mshv_dev == NULL)
> +		return -ENOMEM;
> +
> +	vfio_ops = &mshv_vfio_device_ops;
> +	mshv_dev->device_ops = vfio_ops;
> +	mshv_dev->device_pt = partition;
> +
> +	rc = vfio_ops->device_create(mshv_dev);
> +	if (rc < 0) {
> +		kfree(mshv_dev);
> +		return rc;
> +	}
> +
> +	hlist_add_head(&mshv_dev->device_ptnode, &partition->pt_devices);
> +
> +	mshv_partition_get(partition);
> +	rc = anon_inode_getfd(vfio_ops->device_name, &mshv_device_fops,
> +			      mshv_dev, O_RDWR | O_CLOEXEC);
> +	if (rc < 0)
> +		goto undo_out;
> +
> +	devargk.fd = rc;
> +	if (copy_to_user(uarg, &devargk, sizeof(devargk)))
> +		return -EFAULT;    /* cleanup in mshv_device_fop_release() */

Does this sequence leak the file descriptor if copy_to_user() fails?

The anon_inode_getfd() call installs the file descriptor into the process's 
fd table. If the subsequent copy_to_user() fails, the function returns 
-EFAULT, but the user space application never receives the fd number to 
explicitly close it, resulting in a leaked file descriptor.

Additionally, can this trigger a deadlock?

The ioctl is called with partition->pt_mutex held. If a malicious user 
provides a buffer backed by userfaultfd, the copy_to_user() call will 
block, holding the mutex. Concurrently, another thread could find the 
new fd in /proc/self/fd and call close(), which invokes 
mshv_device_fop_release(). That release function unconditionally attempts 
to acquire partition->pt_mutex, resulting in a deadlock.

Would it be better to separate file allocation and installation by using 
get_unused_fd_flags(), anon_inode_getfile(), and only calling fd_install() 
after copy_to_user() succeeds?

> +
> +	return 0;
> +
> +undo_out:
> +	hlist_del(&mshv_dev->device_ptnode);
> +	vfio_ops->device_release(mshv_dev);    /* will kfree(mshv_dev) */

If a future device type does not implement the device_release callback,
could this result in a NULL pointer dereference?

> +	mshv_partition_put(partition);
> +	return rc;
> +}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260512020259.1678627-1-mrathor@linux.microsoft.com?part=6

[PATCH V3 07/11] mshv: Import data structs around device passthru from hyperv headers

[Mukesh R]

Copy/import from Hyper-V public headers, definitions and declarations that
are related to attaching and detaching of device domains, and building
device ids for those purposes.

Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
---
 include/hyperv/hvgdk_mini.h |  11 ++++
 include/hyperv/hvhdk_mini.h | 112 ++++++++++++++++++++++++++++++++++++
 2 files changed, 123 insertions(+)

diff --git a/include/hyperv/hvgdk_mini.h b/include/hyperv/hvgdk_mini.h
index 6a4e8b9d570f..da622fb06440 100644
--- a/include/hyperv/hvgdk_mini.h
+++ b/include/hyperv/hvgdk_mini.h
@@ -326,6 +326,9 @@ union hv_hypervisor_version_info {
 /* stimer Direct Mode is available */
 #define HV_STIMER_DIRECT_MODE_AVAILABLE			BIT(19)
 
+#define HV_DEVICE_DOMAIN_AVAILABLE			BIT(24)
+#define HV_S1_DEVICE_DOMAIN_AVAILABLE			BIT(25)
+
 /*
  * Implementation recommendations. Indicates which behaviors the hypervisor
  * recommends the OS implement for optimal performance.
@@ -475,6 +478,8 @@ union hv_vp_assist_msr_contents {	 /* HV_REGISTER_VP_ASSIST_PAGE */
 #define HVCALL_MAP_DEVICE_INTERRUPT			0x007c
 #define HVCALL_UNMAP_DEVICE_INTERRUPT			0x007d
 #define HVCALL_RETARGET_INTERRUPT			0x007e
+#define HVCALL_ATTACH_DEVICE                            0x0082
+#define HVCALL_DETACH_DEVICE                            0x0083
 #define HVCALL_NOTIFY_PARTITION_EVENT                   0x0087
 #define HVCALL_ENTER_SLEEP_STATE			0x0084
 #define HVCALL_NOTIFY_PORT_RING_EMPTY			0x008b
@@ -486,9 +491,15 @@ union hv_vp_assist_msr_contents {	 /* HV_REGISTER_VP_ASSIST_PAGE */
 #define HVCALL_GET_VP_INDEX_FROM_APIC_ID		0x009a
 #define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE	0x00af
 #define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_LIST	0x00b0
+#define HVCALL_CREATE_DEVICE_DOMAIN                     0x00b1
+#define HVCALL_ATTACH_DEVICE_DOMAIN                     0x00b2
+#define HVCALL_MAP_DEVICE_GPA_PAGES                     0x00b3
+#define HVCALL_UNMAP_DEVICE_GPA_PAGES                   0x00b4
 #define HVCALL_SIGNAL_EVENT_DIRECT			0x00c0
 #define HVCALL_POST_MESSAGE_DIRECT			0x00c1
 #define HVCALL_DISPATCH_VP				0x00c2
+#define HVCALL_DETACH_DEVICE_DOMAIN                     0x00c4
+#define HVCALL_DELETE_DEVICE_DOMAIN                     0x00c5
 #define HVCALL_GET_GPA_PAGES_ACCESS_STATES		0x00c9
 #define HVCALL_ACQUIRE_SPARSE_SPA_PAGE_HOST_ACCESS	0x00d7
 #define HVCALL_RELEASE_SPARSE_SPA_PAGE_HOST_ACCESS	0x00d8
diff --git a/include/hyperv/hvhdk_mini.h b/include/hyperv/hvhdk_mini.h
index b4cb2fa26e9b..60425052a799 100644
--- a/include/hyperv/hvhdk_mini.h
+++ b/include/hyperv/hvhdk_mini.h
@@ -468,6 +468,32 @@ struct hv_send_ipi_ex { /* HV_INPUT_SEND_SYNTHETIC_CLUSTER_IPI_EX */
 	struct hv_vpset vp_set;
 } __packed;
 
+union hv_attdev_flags {		/* HV_ATTACH_DEVICE_FLAGS */
+	struct {
+		u32 logical_id : 1;
+		u32 resvd0 : 1;
+		u32 ats_enabled : 1;
+		u32 virt_func : 1;
+		u32 shared_irq_child : 1;
+		u32 virt_dev : 1;
+		u32 ats_supported : 1;
+		u32 small_irt : 1;
+		u32 resvd : 24;
+	} __packed;
+	u32 as_uint32;
+};
+
+union hv_dev_pci_caps {		/* HV_DEVICE_PCI_CAPABILITIES */
+	struct {
+		u32 max_pasid_width : 5;
+		u32 invalidate_qdepth : 5;
+		u32 global_inval : 1;
+		u32 prg_response_req : 1;
+		u32 resvd : 20;
+	} __packed;
+	u32 as_uint32;
+};
+
 typedef u16 hv_pci_rid;		/* HV_PCI_RID */
 typedef u16 hv_pci_segment;	/* HV_PCI_SEGMENT */
 typedef u64 hv_logical_device_id;
@@ -547,4 +573,90 @@ union hv_device_id {		/* HV_DEVICE_ID */
 	} acpi;
 } __packed;
 
+struct hv_input_attach_device {         /* HV_INPUT_ATTACH_DEVICE */
+	u64 partition_id;
+	union hv_device_id device_id;
+	union hv_attdev_flags attdev_flags;
+	u8  attdev_vtl;
+	u8  rsvd0;
+	u16 rsvd1;
+	u64 logical_devid;
+	union hv_dev_pci_caps dev_pcicaps;
+	u16 pf_pci_rid;
+	u16 resvd2;
+} __packed;
+
+struct hv_input_detach_device {		/* HV_INPUT_DETACH_DEVICE */
+	u64 partition_id;
+	u64 logical_devid;
+} __packed;
+
+
+/* 3 domain types: stage 1, stage 2, and SOC */
+#define HV_DEVICE_DOMAIN_TYPE_S2  0 /* HV_DEVICE_DOMAIN_ID_TYPE_S2 */
+#define HV_DEVICE_DOMAIN_TYPE_S1  1 /* HV_DEVICE_DOMAIN_ID_TYPE_S1 */
+#define HV_DEVICE_DOMAIN_TYPE_SOC 2 /* HV_DEVICE_DOMAIN_ID_TYPE_SOC */
+
+/* ID for stage 2 default domain and NULL domain */
+#define HV_DEVICE_DOMAIN_ID_S2_DEFAULT 0
+#define HV_DEVICE_DOMAIN_ID_S2_NULL    0xFFFFFFFFULL
+
+union hv_device_domain_id {
+	u64 as_uint64;
+	struct {
+		u32 type : 4;
+		u32 reserved : 28;
+		u32 id;
+	};
+} __packed;
+
+struct hv_input_device_domain { /* HV_INPUT_DEVICE_DOMAIN */
+	u64 partition_id;
+	union hv_input_vtl owner_vtl;
+	u8 padding[7];
+	union hv_device_domain_id domain_id;
+} __packed;
+
+union hv_create_device_domain_flags {	/* HV_CREATE_DEVICE_DOMAIN_FLAGS */
+	u32 as_uint32;
+	struct {
+		u32 forward_progress_required : 1;
+		u32 inherit_owning_vtl : 1;
+		u32 reserved : 30;
+	} __packed;
+} __packed;
+
+struct hv_input_create_device_domain {	/* HV_INPUT_CREATE_DEVICE_DOMAIN */
+	struct hv_input_device_domain device_domain;
+	union hv_create_device_domain_flags create_device_domain_flags;
+} __packed;
+
+struct hv_input_delete_device_domain {	/* HV_INPUT_DELETE_DEVICE_DOMAIN */
+	struct hv_input_device_domain device_domain;
+} __packed;
+
+struct hv_input_attach_device_domain {	/* HV_INPUT_ATTACH_DEVICE_DOMAIN */
+	struct hv_input_device_domain device_domain;
+	union hv_device_id device_id;
+} __packed;
+
+struct hv_input_detach_device_domain {	/* HV_INPUT_DETACH_DEVICE_DOMAIN */
+	u64 partition_id;
+	union hv_device_id device_id;
+} __packed;
+
+struct hv_input_map_device_gpa_pages {	/* HV_INPUT_MAP_DEVICE_GPA_PAGES */
+	struct hv_input_device_domain device_domain;
+	union hv_input_vtl target_vtl;
+	u8 padding[3];
+	u32 map_flags;
+	u64 target_device_va_base;
+	u64 gpa_page_list[];
+} __packed;
+
+struct hv_input_unmap_device_gpa_pages {  /* HV_INPUT_UNMAP_DEVICE_GPA_PAGES */
+	struct hv_input_device_domain device_domain;
+	u64 target_device_va_base;
+} __packed;
+
 #endif /* _HV_HVHDK_MINI_H */
-- 
2.51.2.vfs.0.1

[PATCH V3 08/11] PCI: hv: VMBus and PCI device IDs for PCI passthru

[Mukesh R]

On Hyper-V, most hypercalls related to PCI passthru to map/unmap regions,
interrupts, etc need a device ID as a parameter. This device ID refers
to that specific device during the lifetime of passthru.

An L1VH VM only contains VMBus based devices. A device ID for a VMBus
device is slightly different in that it uses the hv_pcibus_device info
for building it to make sure it matches exactly what the hypervisor
expects. This VMBus based device ID is needed when attaching devices in
an L1VH based guest VM. Add a function to build and export it. Before
building it, a check is done to make sure the device is a valid VMBus
device.

In remaining cases, PCI device ID is used. So, also make PCI device ID
build function hv_build_devid_type_pci() public.

Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
---
 arch/x86/hyperv/irqdomain.c         |  9 +++++----
 arch/x86/include/asm/mshyperv.h     |  6 ++++++
 drivers/pci/controller/pci-hyperv.c | 24 ++++++++++++++++++++++++
 include/asm-generic/mshyperv.h      | 11 +++++++++++
 4 files changed, 46 insertions(+), 4 deletions(-)

diff --git a/arch/x86/hyperv/irqdomain.c b/arch/x86/hyperv/irqdomain.c
index b3ad50a874dc..8780573a4332 100644
--- a/arch/x86/hyperv/irqdomain.c
+++ b/arch/x86/hyperv/irqdomain.c
@@ -112,7 +112,7 @@ static int get_rid_cb(struct pci_dev *pdev, u16 alias, void *data)
 	return 0;
 }
 
-static union hv_device_id hv_build_devid_type_pci(struct pci_dev *pdev)
+u64 hv_build_devid_type_pci(struct pci_dev *pdev)
 {
 	int pos;
 	union hv_device_id hv_devid;
@@ -172,8 +172,9 @@ static union hv_device_id hv_build_devid_type_pci(struct pci_dev *pdev)
 	}
 
 out:
-	return hv_devid;
+	return hv_devid.as_uint64;
 }
+EXPORT_SYMBOL_GPL(hv_build_devid_type_pci);
 
 /*
  * hv_map_msi_interrupt() - Map the MSI IRQ in the hypervisor.
@@ -196,7 +197,7 @@ int hv_map_msi_interrupt(struct irq_data *data,
 
 	msidesc = irq_data_get_msi_desc(data);
 	pdev = msi_desc_to_pci_dev(msidesc);
-	hv_devid = hv_build_devid_type_pci(pdev);
+	hv_devid.as_uint64 = hv_build_devid_type_pci(pdev);
 	cpu = cpumask_first(irq_data_get_effective_affinity_mask(data));
 
 	return hv_map_interrupt(hv_devid, false, cpu, cfg->vector,
@@ -271,7 +272,7 @@ static int hv_unmap_msi_interrupt(struct pci_dev *pdev,
 {
 	union hv_device_id hv_devid;
 
-	hv_devid = hv_build_devid_type_pci(pdev);
+	hv_devid.as_uint64 = hv_build_devid_type_pci(pdev);
 	return hv_unmap_interrupt(hv_devid.as_uint64, irq_entry);
 }
 
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index f64393e853ee..2ef34001f8d3 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -248,6 +248,12 @@ void hv_crash_asm_end(void);
 static inline void hv_root_crash_init(void) {}
 #endif  /* CONFIG_MSHV_ROOT && CONFIG_CRASH_DUMP */
 
+#if IS_ENABLED(CONFIG_HYPERV_IOMMU)
+u64 hv_build_devid_type_pci(struct pci_dev *pdev);
+#else
+static inline u64 hv_build_devid_type_pci(struct pci_dev *pdev) { return 0; }
+#endif /* IS_ENABLED(CONFIG_HYPERV_IOMMU) */
+
 #else /* CONFIG_HYPERV */
 static inline void hyperv_init(void) {}
 static inline void hyperv_setup_mmu_ops(void) {}
diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index cfc8fa403dad..50d793ca8f31 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -573,6 +573,7 @@ struct hv_pci_compl {
 };
 
 static void hv_pci_onchannelcallback(void *context);
+static bool hv_vmbus_pci_device(struct pci_bus *pbus);
 
 #ifdef CONFIG_X86
 #define DELIVERY_MODE		APIC_DELIVERY_MODE_FIXED
@@ -1005,6 +1006,24 @@ static struct irq_domain *hv_pci_get_root_domain(void)
 static void hv_arch_irq_unmask(struct irq_data *data) { }
 #endif /* CONFIG_ARM64 */
 
+u64 hv_pci_vmbus_device_id(struct pci_dev *pdev)
+{
+	struct hv_pcibus_device *hbus;
+	struct pci_bus *pbus = pdev->bus;
+
+	if (!hv_vmbus_pci_device(pbus))
+		return 0;
+
+	hbus = container_of(pbus->sysdata, struct hv_pcibus_device, sysdata);
+
+	return	(hbus->hdev->dev_instance.b[5] << 24) |
+		(hbus->hdev->dev_instance.b[4] << 16) |
+		(hbus->hdev->dev_instance.b[7] << 8) |
+		(hbus->hdev->dev_instance.b[6] & 0xf8) |
+		PCI_FUNC(pdev->devfn);
+}
+EXPORT_SYMBOL_GPL(hv_pci_vmbus_device_id);
+
 /**
  * hv_pci_generic_compl() - Invoked for a completion packet
  * @context:		Set up by the sender of the packet.
@@ -1403,6 +1422,11 @@ static struct pci_ops hv_pcifront_ops = {
 	.write = hv_pcifront_write_config,
 };
 
+static bool hv_vmbus_pci_device(struct pci_bus *pbus)
+{
+	return pbus->ops == &hv_pcifront_ops;
+}
+
 /*
  * Paravirtual backchannel
  *
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index e8cbc4e3f7ad..25ac7ca0fd8b 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -204,6 +204,9 @@ extern u64 (*hv_read_reference_counter)(void);
 /* Sentinel value for an uninitialized entry in hv_vp_index array */
 #define VP_INVAL	U32_MAX
 
+/* Forward declarations */
+struct pci_dev;
+
 int __init hv_common_init(void);
 void __init hv_get_partition_id(void);
 void __init hv_common_free(void);
@@ -316,6 +319,14 @@ void hv_para_set_synic_register(unsigned int reg, u64 val);
 void hyperv_cleanup(void);
 bool hv_query_ext_cap(u64 cap_query);
 void hv_setup_dma_ops(struct device *dev, bool coherent);
+
+#if IS_ENABLED(CONFIG_PCI_HYPERV)
+u64 hv_pci_vmbus_device_id(struct pci_dev *pdev);
+#else
+static inline u64 hv_pci_vmbus_device_id(struct pci_dev *pdev)
+{ return 0; }
+#endif /* IS_ENABLED(CONFIG_PCI_HYPERV) */
+
 #else /* CONFIG_HYPERV */
 static inline void hv_identify_partition_type(void) {}
 static inline bool hv_is_hyperv_initialized(void) { return false; }
-- 
2.51.2.vfs.0.1

Re: [PATCH V3 08/11] PCI: hv: VMBus and PCI device IDs for PCI passthru

[Bjorn Helgaas]

On Mon, May 11, 2026 at 07:02:56PM -0700, Mukesh R wrote:
> On Hyper-V, most hypercalls related to PCI passthru to map/unmap regions,
> interrupts, etc need a device ID as a parameter. This device ID refers
> to that specific device during the lifetime of passthru.
> 
> An L1VH VM only contains VMBus based devices. A device ID for a VMBus
> device is slightly different in that it uses the hv_pcibus_device info
> for building it to make sure it matches exactly what the hypervisor
> expects. This VMBus based device ID is needed when attaching devices in
> an L1VH based guest VM. Add a function to build and export it. Before
> building it, a check is done to make sure the device is a valid VMBus
> device.
> 
> In remaining cases, PCI device ID is used. So, also make PCI device ID
> build function hv_build_devid_type_pci() public.

The subject line should start with a verb to help say what this patch
does.  I guess it's something about adding a function to build the
device IDs expected by the hypervisor?  Would be good to include the
function name too, e.g., something like this:

  PCI: hv: Add foo() to build hypervisor device IDs

Re: [PATCH V3 08/11] PCI: hv: VMBus and PCI device IDs for PCI passthru

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] Conflicting declarations and missing `#ifdef` guards for `hv_build_devid_type_pci()` cause build failures under certain Kconfig combinations.
--

commit 086da02227f217e959d3022c592e1b8698814d5b
Author: Mukesh R <mrathor@linux.microsoft.com>

PCI: hv: VMBus and PCI device IDs for PCI passthru

This commit introduces functions to build and export VMBus and PCI device
IDs for use with Hyper-V PCI passthru. It exposes hv_build_devid_type_pci()
and adds hv_pci_vmbus_device_id() to generate the device IDs expected by
the hypervisor.

> diff --git a/arch/x86/hyperv/irqdomain.c b/arch/x86/hyperv/irqdomain.c
> index b3ad50a874dca..8780573a43326 100644
> --- a/arch/x86/hyperv/irqdomain.c
> +++ b/arch/x86/hyperv/irqdomain.c
> @@ -112,7 +112,7 @@ static int get_rid_cb(struct pci_dev *pdev, u16 alias, void *data)
>  	return 0;
>  }
>  
> -static union hv_device_id hv_build_devid_type_pci(struct pci_dev *pdev)
> +u64 hv_build_devid_type_pci(struct pci_dev *pdev)
>  {
>  	int pos;
[ ... ]
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index f64393e853ee3..2ef34001f8d31 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
[ ... ]
> @@ -248,6 +248,12 @@ void hv_crash_asm_end(void);
>  static inline void hv_root_crash_init(void) {}
>  #endif  /* CONFIG_MSHV_ROOT && CONFIG_CRASH_DUMP */
>  
> +#if IS_ENABLED(CONFIG_HYPERV_IOMMU)
> +u64 hv_build_devid_type_pci(struct pci_dev *pdev);
> +#else
> +static inline u64 hv_build_devid_type_pci(struct pci_dev *pdev) { return 0; }
> +#endif /* IS_ENABLED(CONFIG_HYPERV_IOMMU) */

Will this cause build failures under certain Kconfig combinations?

If CONFIG_PCI_MSI=y and CONFIG_HYPERV_IOMMU=n, arch/x86/hyperv/irqdomain.c
provides a non-static definition of hv_build_devid_type_pci(), but this
header provides a static inline definition, which leads to a redefinition
error.

Conversely, if CONFIG_PCI_MSI=n and CONFIG_HYPERV_IOMMU=y, this header
declares the function, but it is never defined because irqdomain.c is not
compiled, resulting in linker errors.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260512020259.1678627-1-mrathor@linux.microsoft.com?part=8

Re: [PATCH V3 08/11] PCI: hv: VMBus and PCI device IDs for PCI passthru

[Souradeep Chakrabarti]

On Mon, May 11, 2026 at 07:02:56PM -0700, Mukesh R wrote:
> On Hyper-V, most hypercalls related to PCI passthru to map/unmap regions,
> interrupts, etc need a device ID as a parameter. This device ID refers
> to that specific device during the lifetime of passthru.
> 
> An L1VH VM only contains VMBus based devices. A device ID for a VMBus
> device is slightly different in that it uses the hv_pcibus_device info
> for building it to make sure it matches exactly what the hypervisor
> expects. This VMBus based device ID is needed when attaching devices in
> an L1VH based guest VM. Add a function to build and export it. Before
> building it, a check is done to make sure the device is a valid VMBus
> device.
> 
> In remaining cases, PCI device ID is used. So, also make PCI device ID
> build function hv_build_devid_type_pci() public.
>
Reviewed-by: Souradeep Chakrabarti <schakrabarti@microsoft.com>
> Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
> ---
>  arch/x86/hyperv/irqdomain.c         |  9 +++++----
>  arch/x86/include/asm/mshyperv.h     |  6 ++++++
>  drivers/pci/controller/pci-hyperv.c | 24 ++++++++++++++++++++++++
>  include/asm-generic/mshyperv.h      | 11 +++++++++++
>  4 files changed, 46 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/hyperv/irqdomain.c b/arch/x86/hyperv/irqdomain.c
> index b3ad50a874dc..8780573a4332 100644
> --- a/arch/x86/hyperv/irqdomain.c
> +++ b/arch/x86/hyperv/irqdomain.c
> @@ -112,7 +112,7 @@ static int get_rid_cb(struct pci_dev *pdev, u16 alias, void *data)
>  	return 0;
>  }
>  
> -static union hv_device_id hv_build_devid_type_pci(struct pci_dev *pdev)
> +u64 hv_build_devid_type_pci(struct pci_dev *pdev)
>  {
>  	int pos;
>  	union hv_device_id hv_devid;
> @@ -172,8 +172,9 @@ static union hv_device_id hv_build_devid_type_pci(struct pci_dev *pdev)
>  	}
>  
>  out:
> -	return hv_devid;
> +	return hv_devid.as_uint64;
>  }
> +EXPORT_SYMBOL_GPL(hv_build_devid_type_pci);
>  
>  /*
>   * hv_map_msi_interrupt() - Map the MSI IRQ in the hypervisor.
> @@ -196,7 +197,7 @@ int hv_map_msi_interrupt(struct irq_data *data,
>  
>  	msidesc = irq_data_get_msi_desc(data);
>  	pdev = msi_desc_to_pci_dev(msidesc);
> -	hv_devid = hv_build_devid_type_pci(pdev);
> +	hv_devid.as_uint64 = hv_build_devid_type_pci(pdev);
>  	cpu = cpumask_first(irq_data_get_effective_affinity_mask(data));
>  
>  	return hv_map_interrupt(hv_devid, false, cpu, cfg->vector,
> @@ -271,7 +272,7 @@ static int hv_unmap_msi_interrupt(struct pci_dev *pdev,
>  {
>  	union hv_device_id hv_devid;
>  
> -	hv_devid = hv_build_devid_type_pci(pdev);
> +	hv_devid.as_uint64 = hv_build_devid_type_pci(pdev);
>  	return hv_unmap_interrupt(hv_devid.as_uint64, irq_entry);
>  }
>  
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index f64393e853ee..2ef34001f8d3 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -248,6 +248,12 @@ void hv_crash_asm_end(void);
>  static inline void hv_root_crash_init(void) {}
>  #endif  /* CONFIG_MSHV_ROOT && CONFIG_CRASH_DUMP */
>  
> +#if IS_ENABLED(CONFIG_HYPERV_IOMMU)
> +u64 hv_build_devid_type_pci(struct pci_dev *pdev);
> +#else
> +static inline u64 hv_build_devid_type_pci(struct pci_dev *pdev) { return 0; }
> +#endif /* IS_ENABLED(CONFIG_HYPERV_IOMMU) */
> +
>  #else /* CONFIG_HYPERV */
>  static inline void hyperv_init(void) {}
>  static inline void hyperv_setup_mmu_ops(void) {}
> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> index cfc8fa403dad..50d793ca8f31 100644
> --- a/drivers/pci/controller/pci-hyperv.c
> +++ b/drivers/pci/controller/pci-hyperv.c
> @@ -573,6 +573,7 @@ struct hv_pci_compl {
>  };
>  
>  static void hv_pci_onchannelcallback(void *context);
> +static bool hv_vmbus_pci_device(struct pci_bus *pbus);
>  
>  #ifdef CONFIG_X86
>  #define DELIVERY_MODE		APIC_DELIVERY_MODE_FIXED
> @@ -1005,6 +1006,24 @@ static struct irq_domain *hv_pci_get_root_domain(void)
>  static void hv_arch_irq_unmask(struct irq_data *data) { }
>  #endif /* CONFIG_ARM64 */
>  
> +u64 hv_pci_vmbus_device_id(struct pci_dev *pdev)
> +{
> +	struct hv_pcibus_device *hbus;
> +	struct pci_bus *pbus = pdev->bus;
> +
> +	if (!hv_vmbus_pci_device(pbus))
> +		return 0;
> +
> +	hbus = container_of(pbus->sysdata, struct hv_pcibus_device, sysdata);
> +
> +	return	(hbus->hdev->dev_instance.b[5] << 24) |
> +		(hbus->hdev->dev_instance.b[4] << 16) |
> +		(hbus->hdev->dev_instance.b[7] << 8) |
> +		(hbus->hdev->dev_instance.b[6] & 0xf8) |
> +		PCI_FUNC(pdev->devfn);
> +}
> +EXPORT_SYMBOL_GPL(hv_pci_vmbus_device_id);
> +
>  /**
>   * hv_pci_generic_compl() - Invoked for a completion packet
>   * @context:		Set up by the sender of the packet.
> @@ -1403,6 +1422,11 @@ static struct pci_ops hv_pcifront_ops = {
>  	.write = hv_pcifront_write_config,
>  };
>  
> +static bool hv_vmbus_pci_device(struct pci_bus *pbus)
> +{
> +	return pbus->ops == &hv_pcifront_ops;
> +}
> +
>  /*
>   * Paravirtual backchannel
>   *
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index e8cbc4e3f7ad..25ac7ca0fd8b 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -204,6 +204,9 @@ extern u64 (*hv_read_reference_counter)(void);
>  /* Sentinel value for an uninitialized entry in hv_vp_index array */
>  #define VP_INVAL	U32_MAX
>  
> +/* Forward declarations */
> +struct pci_dev;
> +
>  int __init hv_common_init(void);
>  void __init hv_get_partition_id(void);
>  void __init hv_common_free(void);
> @@ -316,6 +319,14 @@ void hv_para_set_synic_register(unsigned int reg, u64 val);
>  void hyperv_cleanup(void);
>  bool hv_query_ext_cap(u64 cap_query);
>  void hv_setup_dma_ops(struct device *dev, bool coherent);
> +
> +#if IS_ENABLED(CONFIG_PCI_HYPERV)
> +u64 hv_pci_vmbus_device_id(struct pci_dev *pdev);
> +#else
> +static inline u64 hv_pci_vmbus_device_id(struct pci_dev *pdev)
> +{ return 0; }
> +#endif /* IS_ENABLED(CONFIG_PCI_HYPERV) */
> +
>  #else /* CONFIG_HYPERV */
>  static inline void hv_identify_partition_type(void) {}
>  static inline bool hv_is_hyperv_initialized(void) { return false; }
> -- 
> 2.51.2.vfs.0.1
> 

Re: [PATCH V3 08/11] PCI: hv: VMBus and PCI device IDs for PCI passthru

[Souradeep Chakrabarti]

On Wed, May 13, 2026 at 08:08:37AM -0700, Souradeep Chakrabarti wrote:
> On Mon, May 11, 2026 at 07:02:56PM -0700, Mukesh R wrote:
> > On Hyper-V, most hypercalls related to PCI passthru to map/unmap regions,
> > interrupts, etc need a device ID as a parameter. This device ID refers
> > to that specific device during the lifetime of passthru.
> > 
> > An L1VH VM only contains VMBus based devices. A device ID for a VMBus
> > device is slightly different in that it uses the hv_pcibus_device info
> > for building it to make sure it matches exactly what the hypervisor
> > expects. This VMBus based device ID is needed when attaching devices in
> > an L1VH based guest VM. Add a function to build and export it. Before
> > building it, a check is done to make sure the device is a valid VMBus
> > device.
> > 
> > In remaining cases, PCI device ID is used. So, also make PCI device ID
> > build function hv_build_devid_type_pci() public.
> >
Reviewed-by: Souradeep Chakrabarti <schakrabarti@linux.microsoft.com>
> Reviewed-by: Souradeep Chakrabarti <schakrabarti@microsoft.com>
> > Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
> > ---
> >  arch/x86/hyperv/irqdomain.c         |  9 +++++----
> >  arch/x86/include/asm/mshyperv.h     |  6 ++++++
> >  drivers/pci/controller/pci-hyperv.c | 24 ++++++++++++++++++++++++
> >  include/asm-generic/mshyperv.h      | 11 +++++++++++
> >  4 files changed, 46 insertions(+), 4 deletions(-)
> > 
> > diff --git a/arch/x86/hyperv/irqdomain.c b/arch/x86/hyperv/irqdomain.c
> > index b3ad50a874dc..8780573a4332 100644
> > --- a/arch/x86/hyperv/irqdomain.c
> > +++ b/arch/x86/hyperv/irqdomain.c
> > @@ -112,7 +112,7 @@ static int get_rid_cb(struct pci_dev *pdev, u16 alias, void *data)
> >  	return 0;
> >  }
> >  
> > -static union hv_device_id hv_build_devid_type_pci(struct pci_dev *pdev)
> > +u64 hv_build_devid_type_pci(struct pci_dev *pdev)
> >  {
> >  	int pos;
> >  	union hv_device_id hv_devid;
> > @@ -172,8 +172,9 @@ static union hv_device_id hv_build_devid_type_pci(struct pci_dev *pdev)
> >  	}
> >  
> >  out:
> > -	return hv_devid;
> > +	return hv_devid.as_uint64;
> >  }
> > +EXPORT_SYMBOL_GPL(hv_build_devid_type_pci);
> >  
> >  /*
> >   * hv_map_msi_interrupt() - Map the MSI IRQ in the hypervisor.
> > @@ -196,7 +197,7 @@ int hv_map_msi_interrupt(struct irq_data *data,
> >  
> >  	msidesc = irq_data_get_msi_desc(data);
> >  	pdev = msi_desc_to_pci_dev(msidesc);
> > -	hv_devid = hv_build_devid_type_pci(pdev);
> > +	hv_devid.as_uint64 = hv_build_devid_type_pci(pdev);
> >  	cpu = cpumask_first(irq_data_get_effective_affinity_mask(data));
> >  
> >  	return hv_map_interrupt(hv_devid, false, cpu, cfg->vector,
> > @@ -271,7 +272,7 @@ static int hv_unmap_msi_interrupt(struct pci_dev *pdev,
> >  {
> >  	union hv_device_id hv_devid;
> >  
> > -	hv_devid = hv_build_devid_type_pci(pdev);
> > +	hv_devid.as_uint64 = hv_build_devid_type_pci(pdev);
> >  	return hv_unmap_interrupt(hv_devid.as_uint64, irq_entry);
> >  }
> >  
> > diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> > index f64393e853ee..2ef34001f8d3 100644
> > --- a/arch/x86/include/asm/mshyperv.h
> > +++ b/arch/x86/include/asm/mshyperv.h
> > @@ -248,6 +248,12 @@ void hv_crash_asm_end(void);
> >  static inline void hv_root_crash_init(void) {}
> >  #endif  /* CONFIG_MSHV_ROOT && CONFIG_CRASH_DUMP */
> >  
> > +#if IS_ENABLED(CONFIG_HYPERV_IOMMU)
> > +u64 hv_build_devid_type_pci(struct pci_dev *pdev);
> > +#else
> > +static inline u64 hv_build_devid_type_pci(struct pci_dev *pdev) { return 0; }
> > +#endif /* IS_ENABLED(CONFIG_HYPERV_IOMMU) */
> > +
> >  #else /* CONFIG_HYPERV */
> >  static inline void hyperv_init(void) {}
> >  static inline void hyperv_setup_mmu_ops(void) {}
> > diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> > index cfc8fa403dad..50d793ca8f31 100644
> > --- a/drivers/pci/controller/pci-hyperv.c
> > +++ b/drivers/pci/controller/pci-hyperv.c
> > @@ -573,6 +573,7 @@ struct hv_pci_compl {
> >  };
> >  
> >  static void hv_pci_onchannelcallback(void *context);
> > +static bool hv_vmbus_pci_device(struct pci_bus *pbus);
> >  
> >  #ifdef CONFIG_X86
> >  #define DELIVERY_MODE		APIC_DELIVERY_MODE_FIXED
> > @@ -1005,6 +1006,24 @@ static struct irq_domain *hv_pci_get_root_domain(void)
> >  static void hv_arch_irq_unmask(struct irq_data *data) { }
> >  #endif /* CONFIG_ARM64 */
> >  
> > +u64 hv_pci_vmbus_device_id(struct pci_dev *pdev)
> > +{
> > +	struct hv_pcibus_device *hbus;
> > +	struct pci_bus *pbus = pdev->bus;
> > +
> > +	if (!hv_vmbus_pci_device(pbus))
> > +		return 0;
> > +
> > +	hbus = container_of(pbus->sysdata, struct hv_pcibus_device, sysdata);
> > +
> > +	return	(hbus->hdev->dev_instance.b[5] << 24) |
> > +		(hbus->hdev->dev_instance.b[4] << 16) |
> > +		(hbus->hdev->dev_instance.b[7] << 8) |
> > +		(hbus->hdev->dev_instance.b[6] & 0xf8) |
> > +		PCI_FUNC(pdev->devfn);
> > +}
> > +EXPORT_SYMBOL_GPL(hv_pci_vmbus_device_id);
> > +
> >  /**
> >   * hv_pci_generic_compl() - Invoked for a completion packet
> >   * @context:		Set up by the sender of the packet.
> > @@ -1403,6 +1422,11 @@ static struct pci_ops hv_pcifront_ops = {
> >  	.write = hv_pcifront_write_config,
> >  };
> >  
> > +static bool hv_vmbus_pci_device(struct pci_bus *pbus)
> > +{
> > +	return pbus->ops == &hv_pcifront_ops;
> > +}
> > +
> >  /*
> >   * Paravirtual backchannel
> >   *
> > diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> > index e8cbc4e3f7ad..25ac7ca0fd8b 100644
> > --- a/include/asm-generic/mshyperv.h
> > +++ b/include/asm-generic/mshyperv.h
> > @@ -204,6 +204,9 @@ extern u64 (*hv_read_reference_counter)(void);
> >  /* Sentinel value for an uninitialized entry in hv_vp_index array */
> >  #define VP_INVAL	U32_MAX
> >  
> > +/* Forward declarations */
> > +struct pci_dev;
> > +
> >  int __init hv_common_init(void);
> >  void __init hv_get_partition_id(void);
> >  void __init hv_common_free(void);
> > @@ -316,6 +319,14 @@ void hv_para_set_synic_register(unsigned int reg, u64 val);
> >  void hyperv_cleanup(void);
> >  bool hv_query_ext_cap(u64 cap_query);
> >  void hv_setup_dma_ops(struct device *dev, bool coherent);
> > +
> > +#if IS_ENABLED(CONFIG_PCI_HYPERV)
> > +u64 hv_pci_vmbus_device_id(struct pci_dev *pdev);
> > +#else
> > +static inline u64 hv_pci_vmbus_device_id(struct pci_dev *pdev)
> > +{ return 0; }
> > +#endif /* IS_ENABLED(CONFIG_PCI_HYPERV) */
> > +
> >  #else /* CONFIG_HYPERV */
> >  static inline void hv_identify_partition_type(void) {}
> >  static inline bool hv_is_hyperv_initialized(void) { return false; }
> > -- 
> > 2.51.2.vfs.0.1
> > 

[PATCH V3 09/11] x86/hyperv: Implement Hyper-V virtual IOMMU

[Mukesh R]

Add a new file to implement management of device domains, mapping and
unmapping of IOMMU memory, and other iommu_ops to fit within the VFIO
framework for PCI passthru on Hyper-V running Linux as baremetal root
or L1VH root. This also implements direct attach mechanism (see below),
a special feature of Hyper-V for PCI passthru, and it is also made to
work within the VFIO framework.

At a high level, during boot the hypervisor creates a default identity
domain and attaches all devices to it. This nicely maps to Linux IOMMU
subsystem IOMMU_DOMAIN_IDENTITY domain. As a result, Linux does not
need to explicitly ask Hyper-V to attach devices and do maps/unmaps
during boot. As mentioned previously, Hyper-V supports two ways to do
PCI passthru:

  1. Device Domain (aka Domain Attach): root must create a device domain
     in the hypervisor, and do map/unmap hypercalls for mapping and
     unmapping guest RAM for DMA. All hypervisor communications use
     device ID of type PCI for identifying and referencing the device.

  2. Direct Attach: the hypervisor will simply use the guest's HW
     page table for mappings, thus the root need not map/unmap guest
     memory for DMA. As such, direct attach passthru setup during guest
     boot is extremely fast. A direct attached device must always be
     referenced via logical device ID and not via the PCI device ID.

At present, L1VH root only supports direct attaches. Also direct attach is
default in non-L1VH cases because there are some significant performance
issues with domain attach implementations currently for guests with higher
RAM (say more than 8GB), and that unfortunately cannot be addressed in
the short term.

Co-developed-by: Wei Liu <wei.liu@kernel.org>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
---
 MAINTAINERS                       |   1 +
 arch/x86/kernel/pci-dma.c         |   2 +
 drivers/iommu/Kconfig             |   5 +-
 drivers/iommu/Makefile            |   1 +
 drivers/iommu/hyperv-iommu-root.c | 918 ++++++++++++++++++++++++++++++
 include/asm-generic/mshyperv.h    |  17 +
 include/linux/hyperv.h            |   6 +
 7 files changed, 947 insertions(+), 3 deletions(-)
 create mode 100644 drivers/iommu/hyperv-iommu-root.c

diff --git a/MAINTAINERS b/MAINTAINERS
index f803a6a38fee..8ae040b89a56 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11914,6 +11914,7 @@ F:	drivers/clocksource/hyperv_timer.c
 F:	drivers/hid/hid-hyperv.c
 F:	drivers/hv/
 F:	drivers/input/serio/hyperv-keyboard.c
+F:	drivers/iommu/hyperv-iommu-root.c
 F:	drivers/iommu/hyperv-irq.c
 F:	drivers/net/ethernet/microsoft/
 F:	drivers/net/hyperv/
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 6267363e0189..cfeee6505e17 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -8,6 +8,7 @@
 #include <linux/gfp.h>
 #include <linux/pci.h>
 #include <linux/amd-iommu.h>
+#include <linux/hyperv.h>
 
 #include <asm/proto.h>
 #include <asm/dma.h>
@@ -105,6 +106,7 @@ void __init pci_iommu_alloc(void)
 	gart_iommu_hole_init();
 	amd_iommu_detect();
 	detect_intel_iommu();
+	hv_iommu_detect();
 	swiotlb_init(x86_swiotlb_enable, x86_swiotlb_flags);
 }
 
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index f86262b11416..7909cf4373a6 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -352,13 +352,12 @@ config MTK_IOMMU_V1
 	  if unsure, say N here.
 
 config HYPERV_IOMMU
-	bool "Hyper-V IRQ Handling"
+	bool "Hyper-V IOMMU Unit"
 	depends on HYPERV && X86
 	select IOMMU_API
 	default HYPERV
 	help
-	  Stub IOMMU driver to handle IRQs to support Hyper-V Linux
-	  guest and root partitions.
+	  Hyper-V pseudo IOMMU unit.
 
 config VIRTIO_IOMMU
 	tristate "Virtio IOMMU driver"
diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
index 335ea77cced6..296fbc6ca829 100644
--- a/drivers/iommu/Makefile
+++ b/drivers/iommu/Makefile
@@ -31,6 +31,7 @@ obj-$(CONFIG_EXYNOS_IOMMU) += exynos-iommu.o
 obj-$(CONFIG_FSL_PAMU) += fsl_pamu.o fsl_pamu_domain.o
 obj-$(CONFIG_S390_IOMMU) += s390-iommu.o
 obj-$(CONFIG_HYPERV) += hyperv-irq.o
+obj-$(CONFIG_HYPERV_IOMMU) += hyperv-iommu-root.o
 obj-$(CONFIG_VIRTIO_IOMMU) += virtio-iommu.o
 obj-$(CONFIG_IOMMU_SVA) += iommu-sva.o
 obj-$(CONFIG_IOMMU_IOPF) += io-pgfault.o
diff --git a/drivers/iommu/hyperv-iommu-root.c b/drivers/iommu/hyperv-iommu-root.c
new file mode 100644
index 000000000000..a2e0f6cc78e6
--- /dev/null
+++ b/drivers/iommu/hyperv-iommu-root.c
@@ -0,0 +1,918 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Hyper-V root vIOMMU driver.
+ * Copyright (C) 2026, Microsoft, Inc.
+ */
+
+#include <linux/pci.h>
+#include <linux/dma-map-ops.h>
+#include <linux/interval_tree.h>
+#include <linux/hyperv.h>
+#include "dma-iommu.h"
+#include <asm/iommu.h>
+#include <asm/mshyperv.h>
+
+/* We will not claim these PCI devices, eg hypervisor needs it for debugger */
+static char *pci_devs_to_skip;
+static int __init hv_iommu_setup_skip(char *str)
+{
+	pci_devs_to_skip = str;
+
+	return 0;
+}
+/* hv_iommu_skip=(SSSS:BB:DD.F)(SSSS:BB:DD.F) */
+__setup("hv_iommu_skip=", hv_iommu_setup_skip);
+
+bool hv_no_attdev;	 /* disable direct device attach for passthru */
+EXPORT_SYMBOL_GPL(hv_no_attdev);
+static int __init setup_hv_no_attdev(char *str)
+{
+	hv_no_attdev = true;
+	return 0;
+}
+__setup("hv_no_attdev", setup_hv_no_attdev);
+
+/* Iommu device that we export to the world. HyperV supports max of one */
+static struct iommu_device hv_virt_iommu;
+
+struct hv_domain {
+	struct iommu_domain iommu_dom;
+	u32 domid_num;			      /* as opposed to domain_id.type */
+	bool attached_dom;		      /* is this direct attached dom? */
+	u64 partid;			      /* partition id */
+	spinlock_t mappings_lock;	      /* protects mappings_tree */
+	struct rb_root_cached mappings_tree;  /* iova to pa lookup tree */
+};
+
+#define to_hv_domain(d) container_of(d, struct hv_domain, iommu_dom)
+
+struct hv_iommu_mapping {
+	phys_addr_t paddr;
+	struct interval_tree_node iova;
+	u32 flags;
+};
+
+/*
+ * By default, during boot the hypervisor creates one Stage 2 (S2) default
+ * domain. Stage 2 means that the page table is controlled by the hypervisor.
+ * It has two types:
+ *   S2 default: access to entire root partition memory. This for us easily
+ *		 maps to IOMMU_DOMAIN_IDENTITY in the iommu subsystem, and
+ *		 is called HV_DEVICE_DOMAIN_ID_S2_DEFAULT in the hypervisor.
+ *   S2 NULL: Blocks everything except RMRR
+ *
+ * Device Management:
+ *   There are two ways to manage device attaches to domains:
+ *     1. Domain Attach: A device domain is created in the hypervisor, the
+ *			 device is attached to this domain, and then memory
+ *			 ranges are mapped in the map callbacks.
+ *     2. Direct Attach: No need to create a domain in the hypervisor for direct
+ *			 attached devices. A hypercall is made to tell the
+ *			 hypervisor to attach the device to a guest. There is
+ *			 no need for explicit memory mappings because the
+ *			 hypervisor will just use the guest HW page table.
+ *
+ * Since a direct attach is much faster, it is the default. This can be
+ * changed via hv_no_attdev.
+ *
+ * L1VH: hypervisor only supports direct attach. Also, there is no S2 default
+ *	 in the hypervisor, so no explicit attach to S2 needed.
+ */
+
+/*
+ * Create dummy domains to correspond to hypervisor prebuilt default identity
+ * and null domains (dummy because we do not make hypercalls to create them).
+ */
+static struct hv_domain hv_def_identity_dom;
+static struct hv_domain hv_null_dom;
+
+static bool hv_special_domain(struct hv_domain *hvdom)
+{
+	return hvdom == &hv_def_identity_dom || hvdom == &hv_null_dom;
+}
+
+struct iommu_domain_geometry default_geometry = (struct iommu_domain_geometry) {
+	.aperture_start = 0,
+	.aperture_end = -1UL,
+	.force_aperture = true,
+};
+
+#define HV_IOMMU_PGSIZES SZ_4K  /* for now, to be enhanced */
+
+static u32 unique_id;	      /* unique numeric id of a new domain */
+
+static void hv_iommu_detach_dev(struct hv_domain *hvdom, struct device *dev);
+static size_t hv_iommu_unmap_pages(struct iommu_domain *immdom, ulong iova,
+				   size_t pgsize, size_t pgcount,
+				   struct iommu_iotlb_gather *gather);
+
+/*
+ * If the current thread is a VMM thread, return the partition id of the VM it
+ * is managing, else return HV_PARTITION_ID_INVALID.
+ */
+u64 hv_get_current_partid(void)
+{
+	u64 (*fn)(void);
+	u64 ptid;
+
+	fn = symbol_get(mshv_current_partid);
+	if (!fn)
+		return HV_PARTITION_ID_INVALID;
+
+	ptid = fn();
+	symbol_put(mshv_current_partid);
+
+	return ptid;
+}
+EXPORT_SYMBOL_GPL(hv_get_current_partid);
+
+/* If this is a VMM thread, then this domain is for a guest vm */
+static bool hv_curr_thread_is_vmm(void)
+{
+	return hv_get_current_partid() != HV_PARTITION_ID_INVALID;
+}
+
+/* As opposed to some host app like SPDK etc... */
+static bool hv_dom_owner_is_vmm(struct hv_domain *hvdom)
+{
+	return hvdom && hvdom->partid != HV_PARTITION_ID_INVALID;
+}
+
+static bool hv_iommu_capable(struct device *dev, enum iommu_cap cap)
+{
+	switch (cap) {
+	case IOMMU_CAP_CACHE_COHERENCY:
+		return true;
+	default:
+		return false;
+	}
+}
+
+/*
+ * Check if given pci device is a direct attached device. Caller must have
+ * verified pdev is a valid pci device.
+ */
+bool hv_pcidev_is_attached_dev(struct pci_dev *pdev)
+{
+	struct iommu_domain *iommu_domain;
+	struct hv_domain *hvdom;
+	struct device *dev = &pdev->dev;
+
+	iommu_domain = iommu_get_domain_for_dev(dev);
+	if (iommu_domain) {
+		hvdom = to_hv_domain(iommu_domain);
+		return hvdom->attached_dom;
+	}
+
+	return false;
+}
+EXPORT_SYMBOL_GPL(hv_pcidev_is_attached_dev);
+
+bool hv_pcidev_is_pthru_dev(struct pci_dev *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct hv_domain *hvdom = dev_iommu_priv_get(dev);
+
+	if (hvdom && !hv_special_domain(hvdom))
+		return true;
+
+	return false;
+}
+EXPORT_SYMBOL_GPL(hv_pcidev_is_pthru_dev);
+
+/* Build device id for direct attached devices */
+static u64 hv_build_devid_type_logical(struct pci_dev *pdev)
+{
+	hv_pci_segment segment;
+	union hv_device_id hv_devid;
+	union hv_pci_bdf bdf = {.as_uint16 = 0};
+	u32 rid = PCI_DEVID(pdev->bus->number, pdev->devfn);
+
+	segment = pci_domain_nr(pdev->bus);
+	bdf.bus = PCI_BUS_NUM(rid);
+	bdf.device = PCI_SLOT(rid);
+	bdf.function = PCI_FUNC(rid);
+
+	hv_devid.as_uint64 = 0;
+	hv_devid.device_type = HV_DEVICE_TYPE_LOGICAL;
+	hv_devid.logical.id = (u64)segment << 16 | bdf.as_uint16;
+
+	return hv_devid.as_uint64;
+}
+
+u64 hv_build_devid_oftype(struct pci_dev *pdev, enum hv_device_type type)
+{
+	if (type == HV_DEVICE_TYPE_LOGICAL) {
+		if (hv_l1vh_partition())
+			return hv_pci_vmbus_device_id(pdev);
+		else
+			return hv_build_devid_type_logical(pdev);
+	} else if (type == HV_DEVICE_TYPE_PCI)
+#ifdef CONFIG_X86
+		return hv_build_devid_type_pci(pdev);
+#else
+		return 0;
+#endif
+	return 0;
+}
+EXPORT_SYMBOL_GPL(hv_build_devid_oftype);
+
+/* Create a new device domain in the hypervisor */
+static int hv_iommu_create_hyp_devdom(struct hv_domain *hvdom)
+{
+	u64 status;
+	struct hv_input_device_domain *ddp;
+	struct hv_input_create_device_domain *input;
+	unsigned long flags;
+
+	local_irq_save(flags);
+	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
+	memset(input, 0, sizeof(*input));
+
+	ddp = &input->device_domain;
+	ddp->partition_id = HV_PARTITION_ID_SELF;
+	ddp->domain_id.type = HV_DEVICE_DOMAIN_TYPE_S2;
+	ddp->domain_id.id = hvdom->domid_num;
+
+	input->create_device_domain_flags.forward_progress_required = 1;
+	input->create_device_domain_flags.inherit_owning_vtl = 0;
+
+	status = hv_do_hypercall(HVCALL_CREATE_DEVICE_DOMAIN, input, NULL);
+
+	local_irq_restore(flags);
+
+	if (!hv_result_success(status))
+		hv_status_err(status, "\n");
+
+	return hv_result_to_errno(status);
+}
+
+static struct iommu_domain *hv_iommu_domain_alloc_paging(struct device *dev)
+{
+	struct hv_domain *hvdom;
+	int rc;
+
+	if (hv_l1vh_partition() && !hv_curr_thread_is_vmm()) {
+		pr_err("Hyper-V: l1vh iommu does not support host devices\n");
+		return NULL;
+	}
+
+	hvdom = kzalloc(sizeof(struct hv_domain), GFP_KERNEL);
+	if (hvdom == NULL)
+		return NULL;
+
+	spin_lock_init(&hvdom->mappings_lock);
+	hvdom->mappings_tree = RB_ROOT_CACHED;
+
+	/* Called under iommu group mutex, so single threaded */
+	if (++unique_id == HV_DEVICE_DOMAIN_ID_S2_NULL)   /* ie, UINTMAX */
+		goto out_err;
+
+	hvdom->domid_num = unique_id;
+	hvdom->partid = hv_get_current_partid();
+	hvdom->iommu_dom.geometry = default_geometry;
+	hvdom->iommu_dom.pgsize_bitmap = HV_IOMMU_PGSIZES;
+
+	/* For guests, by default we do direct attaches, so no domain in hyp */
+	if (hv_dom_owner_is_vmm(hvdom) && !hv_no_attdev)
+		hvdom->attached_dom = true;
+	else {
+		rc = hv_iommu_create_hyp_devdom(hvdom);
+		if (rc)
+			goto out_err;
+	}
+
+	return &hvdom->iommu_dom;
+
+out_err:
+	unique_id--;
+	kfree(hvdom);
+	return NULL;
+}
+
+static void hv_iommu_domain_free(struct iommu_domain *immdom)
+{
+	struct hv_domain *hvdom = to_hv_domain(immdom);
+	unsigned long flags;
+	u64 status;
+	struct hv_input_delete_device_domain *input;
+
+	if (hv_special_domain(hvdom))
+		return;
+
+	if (!hv_dom_owner_is_vmm(hvdom) || hv_no_attdev) {
+		struct hv_input_device_domain *ddp;
+
+		local_irq_save(flags);
+		input = *this_cpu_ptr(hyperv_pcpu_input_arg);
+		ddp = &input->device_domain;
+		memset(input, 0, sizeof(*input));
+
+		ddp->partition_id = HV_PARTITION_ID_SELF;
+		ddp->domain_id.type = HV_DEVICE_DOMAIN_TYPE_S2;
+		ddp->domain_id.id = hvdom->domid_num;
+
+		status = hv_do_hypercall(HVCALL_DELETE_DEVICE_DOMAIN, input,
+					 NULL);
+		local_irq_restore(flags);
+
+		if (!hv_result_success(status))
+			hv_status_err(status, "\n");
+	}
+
+	kfree(hvdom);
+}
+
+/*
+ * Attach a device to the default domain, or the null domain, or to a domain
+ * previously created in the hypervisor.
+ */
+static int hv_iommu_att_dev2dom(struct hv_domain *hvdom, struct pci_dev *pdev)
+{
+	unsigned long flags;
+	u64 status;
+	enum hv_device_type dev_type;
+	struct hv_input_attach_device_domain *input;
+
+	local_irq_save(flags);
+	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
+	memset(input, 0, sizeof(*input));
+
+	/* For null domain, hvdom->domid_num == HV_DEVICE_DOMAIN_ID_S2_NULL */
+	input->device_domain.partition_id = HV_PARTITION_ID_SELF;
+	input->device_domain.domain_id.type = HV_DEVICE_DOMAIN_TYPE_S2;
+	input->device_domain.domain_id.id = hvdom->domid_num;
+
+	/* NB: Upon guest shutdown, device is re-attached to the default domain
+	 *     without explicit detach.
+	 */
+	if (hv_l1vh_partition())
+		dev_type = HV_DEVICE_TYPE_LOGICAL;
+	else
+		dev_type = HV_DEVICE_TYPE_PCI;
+
+	input->device_id.as_uint64 = hv_build_devid_oftype(pdev, dev_type);
+
+	status = hv_do_hypercall(HVCALL_ATTACH_DEVICE_DOMAIN, input, NULL);
+	local_irq_restore(flags);
+
+	if (!hv_result_success(status))
+		hv_status_err(status, "\n");
+
+	return hv_result_to_errno(status);
+}
+
+/* Caller must have validated that dev is a valid pci dev */
+static int hv_iommu_direct_attach_device(struct pci_dev *pdev, u64 ptid)
+{
+	struct hv_input_attach_device *input;
+	u64 status;
+	int rc;
+	unsigned long flags;
+	union hv_device_id host_devid;
+	enum hv_device_type dev_type;
+
+	if (ptid == HV_PARTITION_ID_INVALID) {
+		pr_err("Hyper-V: Invalid partition id in direct attach\n");
+		return -EINVAL;
+	}
+
+	if (hv_l1vh_partition())
+		dev_type = HV_DEVICE_TYPE_LOGICAL;
+	else
+		dev_type = HV_DEVICE_TYPE_PCI;
+
+	host_devid.as_uint64 = hv_build_devid_oftype(pdev, dev_type);
+
+	do {
+		local_irq_save(flags);
+		input = *this_cpu_ptr(hyperv_pcpu_input_arg);
+		memset(input, 0, sizeof(*input));
+		input->partition_id = ptid;
+		input->device_id = host_devid;
+
+		/* Hypervisor associates logical_id with this device, and in
+		 * some hypercalls like retarget interrupts, logical_id must be
+		 * used instead of the BDF. It is a required parameter.
+		 */
+		input->attdev_flags.logical_id = 1;
+		input->logical_devid =
+			   hv_build_devid_oftype(pdev, HV_DEVICE_TYPE_LOGICAL);
+
+		status = hv_do_hypercall(HVCALL_ATTACH_DEVICE, input, NULL);
+		local_irq_restore(flags);
+
+		if (hv_result(status) == HV_STATUS_INSUFFICIENT_MEMORY) {
+			rc = hv_call_deposit_pages(NUMA_NO_NODE, ptid, 1);
+			if (rc)
+				break;
+		}
+	} while (hv_result(status) == HV_STATUS_INSUFFICIENT_MEMORY);
+
+	if (!hv_result_success(status))
+		hv_status_err(status, "\n");
+
+	return hv_result_to_errno(status);
+}
+
+/* Attach a device for passthru to guest VMs, host apps like SPDK, etc */
+static int hv_iommu_attach_dev(struct iommu_domain *immdom, struct device *dev,
+			       struct iommu_domain *old)
+{
+	struct pci_dev *pdev;
+	int rc;
+	struct hv_domain *hvdom_new = to_hv_domain(immdom);
+	struct hv_domain *hvdom_prev = to_hv_domain(old);
+
+	/* Only allow PCI devices for now */
+	if (!dev_is_pci(dev))
+		return -EINVAL;
+
+	pdev = to_pci_dev(dev);
+
+	if (hv_l1vh_partition() && !hv_special_domain(hvdom_new) &&
+	    !hvdom_new->attached_dom)
+		return -EINVAL;
+
+	/* VFIO does not do explicit detach calls, hence check first if we need
+	 * to detach first. Also, in case of guest shutdown, it's the VMM
+	 * thread that attaches it back to the hv_def_identity_dom, and
+	 * hvdom_prev will not be null then. It is null during boot.
+	 */
+	if (hvdom_prev)
+		if (!hv_l1vh_partition() || !hv_special_domain(hvdom_prev))
+			hv_iommu_detach_dev(hvdom_prev, dev);
+
+	/* l1vh does not have a default S2 domain in the hypervisor */
+	if (hv_l1vh_partition() && hv_special_domain(hvdom_new)) {
+		dev_iommu_priv_set(dev, hvdom_new);  /* sets "private" field */
+		return 0;
+	}
+
+	if (hvdom_new->attached_dom)
+		rc = hv_iommu_direct_attach_device(pdev, hvdom_new->partid);
+	else
+		rc = hv_iommu_att_dev2dom(hvdom_new, pdev);
+
+	if (rc == 0)
+		dev_iommu_priv_set(dev, hvdom_new);  /* sets "private" field */
+	else
+		dev_iommu_priv_set(dev, NULL);
+
+	return rc;
+}
+
+static void hv_iommu_det_dev_from_guest(struct pci_dev *pdev, u64 ptid)
+{
+	struct hv_input_detach_device *input;
+	u64 status, log_devid;
+	unsigned long flags;
+
+	log_devid = hv_build_devid_oftype(pdev, HV_DEVICE_TYPE_LOGICAL);
+
+	local_irq_save(flags);
+	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
+	memset(input, 0, sizeof(*input));
+
+	input->partition_id = ptid;
+	input->logical_devid = log_devid;
+	status = hv_do_hypercall(HVCALL_DETACH_DEVICE, input, NULL);
+	local_irq_restore(flags);
+
+	if (!hv_result_success(status))
+		hv_status_err(status, "\n");
+}
+
+static void hv_iommu_det_dev_from_dom(struct pci_dev *pdev)
+{
+	u64 status, devid;
+	unsigned long flags;
+	struct hv_input_detach_device_domain *input;
+
+	devid = hv_build_devid_oftype(pdev, HV_DEVICE_TYPE_PCI);
+
+	local_irq_save(flags);
+	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
+	memset(input, 0, sizeof(*input));
+
+	input->partition_id = HV_PARTITION_ID_SELF;
+	input->device_id.as_uint64 = devid;
+	status = hv_do_hypercall(HVCALL_DETACH_DEVICE_DOMAIN, input, NULL);
+	local_irq_restore(flags);
+
+	if (!hv_result_success(status))
+		hv_status_err(status, "\n");
+}
+
+static void hv_iommu_detach_dev(struct hv_domain *hvdom, struct device *dev)
+{
+	struct pci_dev *pdev;
+
+	/* See the attach function, only PCI devices for now */
+	if (!dev_is_pci(dev))
+		return;
+
+	pdev = to_pci_dev(dev);
+
+	if (hvdom->attached_dom)
+		hv_iommu_det_dev_from_guest(pdev, hvdom->partid);
+
+		/* Do not clear attached_dom, hv_iommu_unmap_pages happens
+		 * next.
+		 */
+	else
+		hv_iommu_det_dev_from_dom(pdev);
+}
+
+static int hv_iommu_add_tree_mapping(struct hv_domain *hvdom,
+				     unsigned long iova, phys_addr_t paddr,
+				     size_t size, u32 flags)
+{
+	unsigned long irqflags;
+	struct hv_iommu_mapping *mapping;
+
+	mapping = kzalloc(sizeof(*mapping), GFP_ATOMIC);
+	if (!mapping)
+		return -ENOMEM;
+
+	mapping->paddr = paddr;
+	mapping->iova.start = iova;
+	mapping->iova.last = iova + size - 1;
+	mapping->flags = flags;
+
+	spin_lock_irqsave(&hvdom->mappings_lock, irqflags);
+	interval_tree_insert(&mapping->iova, &hvdom->mappings_tree);
+	spin_unlock_irqrestore(&hvdom->mappings_lock, irqflags);
+
+	return 0;
+}
+
+static size_t hv_iommu_del_tree_mappings(struct hv_domain *hvdom,
+					unsigned long iova, size_t size)
+{
+	unsigned long flags;
+	size_t unmapped = 0;
+	unsigned long last = iova + size - 1;
+	struct hv_iommu_mapping *mapping = NULL;
+	struct interval_tree_node *node, *next;
+
+	spin_lock_irqsave(&hvdom->mappings_lock, flags);
+	next = interval_tree_iter_first(&hvdom->mappings_tree, iova, last);
+	while (next) {
+		node = next;
+		mapping = container_of(node, struct hv_iommu_mapping, iova);
+		next = interval_tree_iter_next(node, iova, last);
+
+		/* Trying to split a mapping? Not supported for now. */
+		if (mapping->iova.start < iova)
+			break;
+
+		unmapped += mapping->iova.last - mapping->iova.start + 1;
+
+		interval_tree_remove(node, &hvdom->mappings_tree);
+		kfree(mapping);
+	}
+	spin_unlock_irqrestore(&hvdom->mappings_lock, flags);
+
+	return unmapped;
+}
+
+/* Return: must return exact status from the hypercall without changes */
+static u64 hv_iommu_map_pgs(struct hv_domain *hvdom,
+			    unsigned long iova, phys_addr_t paddr,
+			    unsigned long npages, u32 map_flags)
+{
+	u64 status;
+	int i;
+	struct hv_input_map_device_gpa_pages *input;
+	unsigned long flags, pfn;
+
+	local_irq_save(flags);
+	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
+	memset(input, 0, sizeof(*input));
+
+	input->device_domain.partition_id = HV_PARTITION_ID_SELF;
+	input->device_domain.domain_id.type = HV_DEVICE_DOMAIN_TYPE_S2;
+	input->device_domain.domain_id.id = hvdom->domid_num;
+	input->map_flags = map_flags;
+	input->target_device_va_base = iova;
+
+	pfn = paddr >> HV_HYP_PAGE_SHIFT;
+	for (i = 0; i < npages; i++, pfn++)
+		input->gpa_page_list[i] = pfn;
+
+	status = hv_do_rep_hypercall(HVCALL_MAP_DEVICE_GPA_PAGES, npages, 0,
+				     input, NULL);
+
+	local_irq_restore(flags);
+	return status;
+}
+
+#define HV_MAP_DEVICE_GPA_BATCH_SIZE   \
+	((HV_HYP_PAGE_SIZE - sizeof(struct hv_input_map_device_gpa_pages)) \
+			/ sizeof(u64))
+
+/*
+ * The core VFIO code loops over memory ranges calling this function with the
+ * largest pgsize from HV_IOMMU_PGSIZES. cond_resched() is in vfio_iommu_map.
+ */
+static int hv_iommu_map_pages(struct iommu_domain *immdom, ulong iova,
+			      phys_addr_t paddr, size_t pgsize, size_t pgcount,
+			      int prot, gfp_t gfp, size_t *mapped)
+{
+	u32 map_flags;
+	int ret;
+	u64 status;
+	unsigned long npages, done = 0;
+	struct hv_domain *hvdom = to_hv_domain(immdom);
+	size_t size = pgsize * pgcount;
+
+	map_flags = HV_MAP_GPA_READABLE;	/* required */
+	map_flags |= prot & IOMMU_WRITE ? HV_MAP_GPA_WRITABLE : 0;
+
+	ret = hv_iommu_add_tree_mapping(hvdom, iova, paddr, size, map_flags);
+	if (ret)
+		return ret;
+
+	if (hvdom->attached_dom) {
+		*mapped = size;
+		return 0;
+	}
+
+	npages = size >> HV_HYP_PAGE_SHIFT;
+	while (done < npages) {
+		ulong completed, remain = npages - done;
+
+		remain = min(remain, HV_MAP_DEVICE_GPA_BATCH_SIZE);
+
+		status = hv_iommu_map_pgs(hvdom, iova, paddr, remain,
+					  map_flags);
+
+		completed = hv_repcomp(status);
+		done = done + completed;
+		iova = iova + (completed << HV_HYP_PAGE_SHIFT);
+		paddr = paddr + (completed << HV_HYP_PAGE_SHIFT);
+
+		if (hv_result(status) == HV_STATUS_INSUFFICIENT_MEMORY) {
+			ret = hv_call_deposit_pages(NUMA_NO_NODE,
+						    hv_current_partition_id,
+						    256);
+			if (ret)
+				break;
+			continue;
+		}
+		if (!hv_result_success(status))
+			break;
+	}
+
+	if (!hv_result_success(status)) {
+		size_t done_size = done << HV_HYP_PAGE_SHIFT;
+
+		hv_status_err(status, "pgs:%lx/%lx iova:%lx\n",
+			      done, npages, iova);
+		/*
+		 * lookup tree has all mappings [0 - size-1]. Below unmap will
+		 * only remove from [0 - done], we need to remove second chunk
+		 * [done+1 - size-1].
+		 */
+		hv_iommu_del_tree_mappings(hvdom, iova, size - done_size);
+		hv_iommu_unmap_pages(immdom, iova - done_size, HV_HYP_PAGE_SIZE,
+				     done, NULL);
+		if (mapped)
+			*mapped = 0;
+	} else
+		if (mapped)
+			*mapped = size;
+
+	return hv_result_to_errno(status);
+}
+
+static size_t hv_iommu_unmap_pages(struct iommu_domain *immdom, ulong iova,
+				   size_t pgsize, size_t pgcount,
+				   struct iommu_iotlb_gather *gather)
+{
+	unsigned long flags, npages;
+	struct hv_input_unmap_device_gpa_pages *input;
+	u64 status;
+	struct hv_domain *hvdom = to_hv_domain(immdom);
+	size_t unmapped, size = pgsize * pgcount;
+
+	unmapped = hv_iommu_del_tree_mappings(hvdom, iova, size);
+	if (unmapped < size)
+		pr_err("%s: could not delete all mappings (%lx:%lx/%lx)\n",
+		       __func__, iova, unmapped, size);
+
+	if (hvdom->attached_dom)
+		return size;
+
+	npages = size >> HV_HYP_PAGE_SHIFT;
+
+	local_irq_save(flags);
+	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
+	memset(input, 0, sizeof(*input));
+
+	input->device_domain.partition_id = HV_PARTITION_ID_SELF;
+	input->device_domain.domain_id.type = HV_DEVICE_DOMAIN_TYPE_S2;
+	input->device_domain.domain_id.id = hvdom->domid_num;
+	input->target_device_va_base = iova;
+
+	status = hv_do_rep_hypercall(HVCALL_UNMAP_DEVICE_GPA_PAGES, npages,
+				     0, input, NULL);
+	local_irq_restore(flags);
+
+	if (!hv_result_success(status))
+		hv_status_err(status, "\n");
+
+	return unmapped;
+}
+
+static phys_addr_t hv_iommu_iova_to_phys(struct iommu_domain *immdom,
+					 dma_addr_t iova)
+{
+	unsigned long flags;
+	struct hv_iommu_mapping *mapping;
+	struct interval_tree_node *node;
+	u64 paddr = 0;
+	struct hv_domain *hvdom = to_hv_domain(immdom);
+
+	spin_lock_irqsave(&hvdom->mappings_lock, flags);
+	node = interval_tree_iter_first(&hvdom->mappings_tree, iova, iova);
+	if (node) {
+		mapping = container_of(node, struct hv_iommu_mapping, iova);
+		paddr = mapping->paddr + (iova - mapping->iova.start);
+	}
+	spin_unlock_irqrestore(&hvdom->mappings_lock, flags);
+
+	return paddr;
+}
+
+/*
+ * Currently, hypervisor does not provide list of devices it is using
+ * dynamically. So use this to allow users to manually specify devices that
+ * should be skipped. (eg. hypervisor debugger using some network device).
+ */
+static struct iommu_device *hv_iommu_probe_device(struct device *dev)
+{
+	if (!dev_is_pci(dev))
+		return ERR_PTR(-ENODEV);
+
+	if (pci_devs_to_skip && *pci_devs_to_skip) {
+		int rc, pos = 0;
+		int parsed;
+		int segment, bus, slot, func;
+		struct pci_dev *pdev = to_pci_dev(dev);
+
+		do {
+			parsed = 0;
+
+			rc = sscanf(pci_devs_to_skip + pos, " (%x:%x:%x.%x) %n",
+				    &segment, &bus, &slot, &func, &parsed);
+			if (rc)
+				break;
+			if (parsed <= 0)
+				break;
+
+			if (pci_domain_nr(pdev->bus) == segment &&
+			    pdev->bus->number == bus &&
+			    PCI_SLOT(pdev->devfn) == slot &&
+			    PCI_FUNC(pdev->devfn) == func) {
+
+				dev_info(dev, "skipped by Hyper-V IOMMU\n");
+				return ERR_PTR(-ENODEV);
+			}
+			pos += parsed;
+
+		} while (pci_devs_to_skip[pos]);
+	}
+
+	/* Device will be explicitly attached to the default domain, so no need
+	 * to do dev_iommu_priv_set() here.
+	 */
+
+	return &hv_virt_iommu;
+}
+
+static void hv_iommu_probe_finalize(struct device *dev)
+{
+	struct iommu_domain *immdom = iommu_get_domain_for_dev(dev);
+
+	if (immdom && immdom->type == IOMMU_DOMAIN_DMA)
+		iommu_setup_dma_ops(dev, immdom);
+	else
+		set_dma_ops(dev, NULL);
+}
+
+static void hv_iommu_release_device(struct device *dev)
+{
+	struct hv_domain *hvdom = dev_iommu_priv_get(dev);
+
+	/* Need to detach device from device domain if necessary. */
+	if (hvdom)
+		hv_iommu_detach_dev(hvdom, dev);
+
+	dev_iommu_priv_set(dev, NULL);
+	set_dma_ops(dev, NULL);
+}
+
+static struct iommu_group *hv_iommu_device_group(struct device *dev)
+{
+	if (dev_is_pci(dev))
+		return pci_device_group(dev);
+	else
+		return generic_device_group(dev);
+}
+
+static int hv_iommu_def_domain_type(struct device *dev)
+{
+	/* The hypervisor always creates this by default during boot */
+	return IOMMU_DOMAIN_IDENTITY;
+}
+
+static struct iommu_ops hv_iommu_ops = {
+	.capable	    = hv_iommu_capable,
+	.domain_alloc_paging	= hv_iommu_domain_alloc_paging,
+	.probe_device	    = hv_iommu_probe_device,
+	.probe_finalize     = hv_iommu_probe_finalize,
+	.release_device     = hv_iommu_release_device,
+	.def_domain_type    = hv_iommu_def_domain_type,
+	.device_group	    = hv_iommu_device_group,
+	.default_domain_ops = &(const struct iommu_domain_ops) {
+		.attach_dev   = hv_iommu_attach_dev,
+		.map_pages    = hv_iommu_map_pages,
+		.unmap_pages  = hv_iommu_unmap_pages,
+		.iova_to_phys = hv_iommu_iova_to_phys,
+		.free	      = hv_iommu_domain_free,
+	},
+	.owner		    = THIS_MODULE,
+	.identity_domain = &hv_def_identity_dom.iommu_dom,
+	.blocked_domain  = &hv_null_dom.iommu_dom,
+};
+
+static const struct iommu_domain_ops hv_special_domain_ops = {
+	.attach_dev = hv_iommu_attach_dev,
+};
+
+static void __init hv_initialize_special_domains(void)
+{
+	hv_def_identity_dom.iommu_dom.type = IOMMU_DOMAIN_IDENTITY;
+	hv_def_identity_dom.iommu_dom.ops = &hv_special_domain_ops;
+	hv_def_identity_dom.iommu_dom.owner = &hv_iommu_ops;
+	hv_def_identity_dom.iommu_dom.geometry = default_geometry;
+	hv_def_identity_dom.domid_num = HV_DEVICE_DOMAIN_ID_S2_DEFAULT; /* 0 */
+
+	hv_null_dom.iommu_dom.type = IOMMU_DOMAIN_BLOCKED;
+	hv_null_dom.iommu_dom.ops = &hv_special_domain_ops;
+	hv_null_dom.iommu_dom.owner = &hv_iommu_ops;
+	hv_null_dom.iommu_dom.geometry = default_geometry;
+	hv_null_dom.domid_num = HV_DEVICE_DOMAIN_ID_S2_NULL;  /* INTMAX */
+}
+
+static int __init hv_iommu_init(void)
+{
+	int ret;
+	struct iommu_device *iommup = &hv_virt_iommu;
+
+	if (!hv_is_hyperv_initialized())
+		return -ENODEV;
+
+	ret = iommu_device_sysfs_add(iommup, NULL, NULL, "%s", "hyperv-iommu");
+	if (ret) {
+		pr_err("Hyper-V: iommu_device_sysfs_add failed: %d\n", ret);
+		return ret;
+	}
+
+	/* This must come before iommu_device_register because the latter calls
+	 * into the hooks.
+	 */
+	hv_initialize_special_domains();
+
+	ret = iommu_device_register(iommup, &hv_iommu_ops, NULL);
+	if (ret) {
+		pr_err("Hyper-V: iommu_device_register failed: %d\n", ret);
+		goto err_sysfs_remove;
+	}
+
+	pr_info("Hyper-V IOMMU initialized\n");
+
+	return 0;
+
+err_sysfs_remove:
+	iommu_device_sysfs_remove(iommup);
+	return ret;
+}
+
+void __init hv_iommu_detect(void)
+{
+	if (no_iommu || iommu_detected)
+		return;
+
+	/* For l1vh, always expose an iommu unit */
+	if (!hv_l1vh_partition())
+		if (!(ms_hyperv.misc_features & HV_DEVICE_DOMAIN_AVAILABLE))
+			return;
+
+	iommu_detected = 1;
+	x86_init.iommu.iommu_init = hv_iommu_init;
+
+	pci_request_acs();
+}
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index 25ac7ca0fd8b..8d5c610da99a 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -327,6 +327,23 @@ static inline u64 hv_pci_vmbus_device_id(struct pci_dev *pdev)
 { return 0; }
 #endif /* IS_ENABLED(CONFIG_PCI_HYPERV) */
 
+#if IS_ENABLED(CONFIG_HYPERV_IOMMU)
+u64 hv_get_current_partid(void);
+bool hv_pcidev_is_attached_dev(struct pci_dev *pdev);
+bool hv_pcidev_is_pthru_dev(struct pci_dev *pdev);
+u64 hv_build_devid_oftype(struct pci_dev *pdev, enum hv_device_type type);
+#else
+static inline bool hv_pcidev_is_attached_dev(struct pci_dev *pdev)
+{ return false; }
+static inline bool hv_pcidev_is_pthru_dev(struct pci_dev *pdev)
+{ return false; }
+static inline u64 hv_build_devid_oftype(struct pci_dev *pdev,
+					enum hv_device_type type)
+{ return 0; }
+static inline u64 hv_get_current_partid(void)
+{ return HV_PARTITION_ID_INVALID; }
+#endif /* IS_ENABLED(CONFIG_HYPERV_IOMMU) */
+
 #else /* CONFIG_HYPERV */
 static inline void hv_identify_partition_type(void) {}
 static inline bool hv_is_hyperv_initialized(void) { return false; }
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 5459e776ec17..6eee1cbf6f23 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -1769,4 +1769,10 @@ static inline unsigned long virt_to_hvpfn(void *addr)
 #define HVPFN_DOWN(x)	((x) >> HV_HYP_PAGE_SHIFT)
 #define page_to_hvpfn(page)	(page_to_pfn(page) * NR_HV_HYP_PAGES_IN_PAGE)
 
+#ifdef CONFIG_HYPERV_IOMMU
+void __init hv_iommu_detect(void);
+#else
+static inline void hv_iommu_detect(void) { }
+#endif /* CONFIG_HYPERV_IOMMU */
+
 #endif /* _HYPERV_H */
-- 
2.51.2.vfs.0.1

Re: [PATCH V3 09/11] x86/hyperv: Implement Hyper-V virtual IOMMU

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 10 potential issue(s) to consider:
- [Critical] `hv_iommu_unmap_pages` makes a rep hypercall but ignores the completion count, leaving pages permanently mapped.
- [Critical] Integer truncation in `hv_iommu_unmap_pages` causes incomplete hardware unmapping.
- [Critical] Global `unique_id` data race leads to IOMMU domain collisions and cross-VM DMA sharing.
- [High] The `sscanf` return value check in `hv_iommu_probe_device` breaks the loop on success instead of failure.
- [High] Partial unmaps corrupt the interval tree state, desynchronizing hardware and software.
- [High] Unsafe interval tree iteration leads to skipped nodes during removal.
- [High] Memory leak of interval tree nodes on domain free.
- [High] Ignoring `gfp` flags causes premature OOM and risks sleeping in atomic context.
- [Medium] Missing NULL check on `mapped` pointer in fast path.
- [Low] The `__setup` handlers violate the API by returning 0.
--

commit 4a3c258bcace1805e7afe537c6eb3e451a6fd030
Author: Mukesh R <mrathor@linux.microsoft.com>

x86/hyperv: Implement Hyper-V virtual IOMMU

Add a new file to implement management of device domains, mapping and
unmapping of IOMMU memory, and other iommu_ops to fit within the VFIO
framework for PCI passthru on Hyper-V running Linux as baremetal root
or L1VH root.

> diff --git a/drivers/iommu/hyperv-iommu-root.c b/drivers/iommu/hyperv-iommu-root.c
> new file mode 100644
> index 0000000000000..a2e0f6cc78e66
> --- /dev/null
> +++ b/drivers/iommu/hyperv-iommu-root.c

[ ... ]

> +static char *pci_devs_to_skip;
> +static int __init hv_iommu_setup_skip(char *str)
> +{
> +	pci_devs_to_skip = str;
> +
> +	return 0;
> +}

Should this return 1 instead of 0? Returning 0 causes the kernel to print an
unknown command line parameters warning and passes the parameters to the init
process.

> +/* hv_iommu_skip=(SSSS:BB:DD.F)(SSSS:BB:DD.F) */
> +__setup("hv_iommu_skip=", hv_iommu_setup_skip);
> +
> +bool hv_no_attdev;	 /* disable direct device attach for passthru */
> +EXPORT_SYMBOL_GPL(hv_no_attdev);
> +static int __init setup_hv_no_attdev(char *str)
> +{
> +	hv_no_attdev = true;
> +	return 0;
> +}

Should this also return 1 instead of 0 to indicate the parameter was handled?

[ ... ]

> +static struct iommu_domain *hv_iommu_domain_alloc_paging(struct device *dev)
> +{
> +	struct hv_domain *hvdom;
> +	int rc;

[ ... ]

> +	/* Called under iommu group mutex, so single threaded */
> +	if (++unique_id == HV_DEVICE_DOMAIN_ID_S2_NULL)   /* ie, UINTMAX */
> +		goto out_err;

Can this increment of unique_id race if called concurrently?

iommu_domain_alloc() can be called by subsystems without holding global or
group locks. If multiple allocations race, it could assign identical domid_num
values to different domains, which might place them in the same S2 domain.

[ ... ]

> +static void hv_iommu_domain_free(struct iommu_domain *immdom)
> +{
> +	struct hv_domain *hvdom = to_hv_domain(immdom);
> +	unsigned long flags;
> +	u64 status;
> +	struct hv_input_delete_device_domain *input;
> +
> +	if (hv_special_domain(hvdom))
> +		return;
> +
> +	if (!hv_dom_owner_is_vmm(hvdom) || hv_no_attdev) {

[ ... ]

> +	}
> +
> +	kfree(hvdom);
> +}

Does this code leak the interval tree nodes?

It looks like the remaining struct hv_iommu_mapping nodes in
hvdom->mappings_tree are not freed before kfree(hvdom).

[ ... ]

> +static int hv_iommu_add_tree_mapping(struct hv_domain *hvdom,
> +				     unsigned long iova, phys_addr_t paddr,
> +				     size_t size, u32 flags)
> +{
> +	unsigned long irqflags;
> +	struct hv_iommu_mapping *mapping;
> +
> +	mapping = kzalloc(sizeof(*mapping), GFP_ATOMIC);

Should this use the gfp flag passed into hv_iommu_map_pages() instead of
GFP_ATOMIC? It might avoid failing prematurely under memory pressure when the
caller can sleep.

[ ... ]

> +static size_t hv_iommu_del_tree_mappings(struct hv_domain *hvdom,
> +					unsigned long iova, size_t size)
> +{
> +	unsigned long flags;
> +	size_t unmapped = 0;
> +	unsigned long last = iova + size - 1;
> +	struct hv_iommu_mapping *mapping = NULL;
> +	struct interval_tree_node *node, *next;
> +
> +	spin_lock_irqsave(&hvdom->mappings_lock, flags);
> +	next = interval_tree_iter_first(&hvdom->mappings_tree, iova, last);
> +	while (next) {
> +		node = next;
> +		mapping = container_of(node, struct hv_iommu_mapping, iova);
> +		next = interval_tree_iter_next(node, iova, last);
> +
> +		/* Trying to split a mapping? Not supported for now. */
> +		if (mapping->iova.start < iova)
> +			break;

Does breaking out early here leave stale mappings in the tree?

If the target region is unmapped in hardware, the tracking node would remain,
causing stale lookups. Also, if unmapping the head of a mapping, is the
entire node deleted even though the tail is still mapped?

> +
> +		unmapped += mapping->iova.last - mapping->iova.start + 1;
> +
> +		interval_tree_remove(node, &hvdom->mappings_tree);

Can erasing the node corrupt the iteration?

Since interval_tree_remove() rebalances the tree and alters parent pointers,
calling interval_tree_iter_next(next) on the next loop iteration might skip
overlapping nodes.

[ ... ]

> +static int hv_iommu_map_pages(struct iommu_domain *immdom, ulong iova,
> +			      phys_addr_t paddr, size_t pgsize, size_t pgcount,
> +			      int prot, gfp_t gfp, size_t *mapped)
> +{
> +	u32 map_flags;
> +	int ret;
> +	u64 status;
> +	unsigned long npages, done = 0;
> +	struct hv_domain *hvdom = to_hv_domain(immdom);
> +	size_t size = pgsize * pgcount;
> +
> +	map_flags = HV_MAP_GPA_READABLE;	/* required */
> +	map_flags |= prot & IOMMU_WRITE ? HV_MAP_GPA_WRITABLE : 0;
> +
> +	ret = hv_iommu_add_tree_mapping(hvdom, iova, paddr, size, map_flags);
> +	if (ret)
> +		return ret;
> +
> +	if (hvdom->attached_dom) {
> +		*mapped = size;
> +		return 0;
> +	}

Is it possible for mapped to be NULL here?

The fast path assigns to *mapped without validating the pointer, while later
in the function there are defensive checks like if (mapped).

[ ... ]

> +		if (hv_result(status) == HV_STATUS_INSUFFICIENT_MEMORY) {
> +			ret = hv_call_deposit_pages(NUMA_NO_NODE,
> +						    hv_current_partition_id,
> +						    256);

Could this trigger a sleeping in atomic context bug?

hv_call_deposit_pages() typically performs sleepable allocations, but the
caller of hv_iommu_map_pages() might have provided a non-sleeping gfp flag
which was not forwarded.

[ ... ]

> +static size_t hv_iommu_unmap_pages(struct iommu_domain *immdom, ulong iova,
> +				   size_t pgsize, size_t pgcount,
> +				   struct iommu_iotlb_gather *gather)
> +{
> +	unsigned long flags, npages;
> +	struct hv_input_unmap_device_gpa_pages *input;
> +	u64 status;
> +	struct hv_domain *hvdom = to_hv_domain(immdom);
> +	size_t unmapped, size = pgsize * pgcount;

[ ... ]

> +	npages = size >> HV_HYP_PAGE_SHIFT;
> +
> +	local_irq_save(flags);
> +	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
> +	memset(input, 0, sizeof(*input));
> +
> +	input->device_domain.partition_id = HV_PARTITION_ID_SELF;
> +	input->device_domain.domain_id.type = HV_DEVICE_DOMAIN_TYPE_S2;
> +	input->device_domain.domain_id.id = hvdom->domid_num;
> +	input->target_device_va_base = iova;
> +
> +	status = hv_do_rep_hypercall(HVCALL_UNMAP_DEVICE_GPA_PAGES, npages,
> +				     0, input, NULL);

Can npages be truncated here?

The hypercall parameter rep_count in hv_do_rep_hypercall() expects a u16.
If npages is >= 65536, it would be silently truncated, causing incomplete
unmapping in the hardware.

Does this also need a loop to handle partial completions?

hv_do_rep_hypercall() might only partially complete. Since the completion count
from hv_repcomp(status) is ignored, remaining pages could be left fully
mapped in the hardware.

[ ... ]

> +static struct iommu_device *hv_iommu_probe_device(struct device *dev)
> +{
> +	if (!dev_is_pci(dev))
> +		return ERR_PTR(-ENODEV);
> +
> +	if (pci_devs_to_skip && *pci_devs_to_skip) {
> +		int rc, pos = 0;
> +		int parsed;
> +		int segment, bus, slot, func;
> +		struct pci_dev *pdev = to_pci_dev(dev);
> +
> +		do {
> +			parsed = 0;
> +
> +			rc = sscanf(pci_devs_to_skip + pos, " (%x:%x:%x.%x) %n",
> +				    &segment, &bus, &slot, &func, &parsed);
> +			if (rc)
> +				break;

Should this check for failure instead of success?

sscanf() returns the number of successfully matched items. If it succeeds, rc
will be 4, causing the loop to break prematurely without checking the parsed
values against the device.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260512020259.1678627-1-mrathor@linux.microsoft.com?part=9

[PATCH V3 10/11] mshv: Populate mmio mappings for PCI passthru

[Mukesh R]

Upon guest access, in case of missing mmio mapping, the hypervisor
generates an unmapped gpa intercept. In this path, lookup the PCI
resource pfn for the guest gpa, and ask the hypervisor to map it
via hypercall. The PCI resource pfn is maintained by the VFIO driver,
and obtained via fixup_user_fault call (similar to KVM).

Also, VFIO no longer puts the mmio pfn in vma->vm_pgoff. So, remove
code that is using it to map mmio space. It is broken and will cause
panic.

Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
---
 drivers/hv/mshv_root_main.c | 113 ++++++++++++++++++++++++++++++------
 1 file changed, 96 insertions(+), 17 deletions(-)

diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
index 6ceb5f608589..a7864463961b 100644
--- a/drivers/hv/mshv_root_main.c
+++ b/drivers/hv/mshv_root_main.c
@@ -46,6 +46,9 @@ MODULE_DESCRIPTION("Microsoft Hyper-V root partition VMM interface /dev/mshv");
 #define HV_VP_COUNTER_ROOT_DISPATCH_THREAD_BLOCKED 95
 #endif
 
+static bool hv_nofull_mmio;	/* don't map entire mmio region upon fault */
+module_param(hv_nofull_mmio, bool, 0644);
+
 struct mshv_root mshv_root;
 
 enum hv_scheduler_type hv_scheduler_type;
@@ -641,6 +644,94 @@ mshv_partition_region_by_gfn_get(struct mshv_partition *p, u64 gfn)
 	return region;
 }
 
+/*
+ * Check if uaddr is for mmio range. If yes, return 0 with mmio_pfn filled in
+ * else just return -errno.
+ */
+static int mshv_chk_get_mmio_start_pfn(u64 uaddr, u64 *mmio_pfnp)
+{
+	struct vm_area_struct *vma;
+	bool is_mmio;
+	struct follow_pfnmap_args pfnmap_args;
+	int rc = -EINVAL;
+
+	mmap_read_lock(current->mm);
+	vma = vma_lookup(current->mm, uaddr);
+	is_mmio = vma ? !!(vma->vm_flags & (VM_IO | VM_PFNMAP)) : 0;
+	if (!is_mmio)
+		goto unlock_mmap_out;
+
+	pfnmap_args.vma = vma;
+	pfnmap_args.address = uaddr;
+
+	rc = follow_pfnmap_start(&pfnmap_args);
+	if (rc) {
+		rc = fixup_user_fault(current->mm, uaddr, FAULT_FLAG_WRITE,
+				      NULL);
+		if (rc)
+			goto unlock_mmap_out;
+
+		rc = follow_pfnmap_start(&pfnmap_args);
+		if (rc)
+			goto unlock_mmap_out;
+	}
+
+	*mmio_pfnp = pfnmap_args.pfn;
+	follow_pfnmap_end(&pfnmap_args);
+
+unlock_mmap_out:
+	mmap_read_unlock(current->mm);
+	return rc;
+}
+
+/*
+ * Check if the unmapped gpa belongs to mmio space. If yes, resolve it.
+ *
+ * Returns: True if valid mmio intercept and handled, else false.
+ */
+static bool mshv_handle_unmapped_gpa(struct mshv_vp *vp)
+{
+	struct hv_message *hvmsg = vp->vp_intercept_msg_page;
+	u64 gfn, uaddr, mmio_spa, numpgs;
+	struct mshv_mem_region *rg;
+	int rc = -EINVAL;
+	struct mshv_partition *pt = vp->vp_partition;
+#if defined(CONFIG_X86_64)
+	struct hv_x64_memory_intercept_message *msg =
+		(struct hv_x64_memory_intercept_message *)hvmsg->u.payload;
+#elif defined(CONFIG_ARM64)
+	struct hv_arm64_memory_intercept_message *msg =
+		(struct hv_arm64_memory_intercept_message *)hvmsg->u.payload;
+#endif
+
+	gfn = msg->guest_physical_address >> HV_HYP_PAGE_SHIFT;
+
+	rg = mshv_partition_region_by_gfn_get(pt, gfn);
+	if (rg == NULL)
+		return false;
+	if (rg->mreg_type != MSHV_REGION_TYPE_MMIO)
+		goto put_rg_out;
+
+	uaddr = rg->start_uaddr + ((gfn - rg->start_gfn) << HV_HYP_PAGE_SHIFT);
+
+	rc = mshv_chk_get_mmio_start_pfn(uaddr, &mmio_spa);
+	if (rc)
+		goto put_rg_out;
+
+	if (!hv_nofull_mmio) {		/* default case */
+		mmio_spa = mmio_spa - (gfn - rg->start_gfn);
+		gfn = rg->start_gfn;
+		numpgs = rg->nr_pages;
+	} else
+		numpgs = 1;
+
+	rc = hv_call_map_mmio_pages(pt->pt_id, gfn, mmio_spa, numpgs);
+
+put_rg_out:
+	mshv_region_put(rg);
+	return rc == 0;
+}
+
 /**
  * mshv_handle_gpa_intercept - Handle GPA (Guest Physical Address) intercepts.
  * @vp: Pointer to the virtual processor structure.
@@ -699,6 +790,8 @@ static bool mshv_handle_gpa_intercept(struct mshv_vp *vp)
 static bool mshv_vp_handle_intercept(struct mshv_vp *vp)
 {
 	switch (vp->vp_intercept_msg_page->header.message_type) {
+	case HVMSG_UNMAPPED_GPA:
+		return mshv_handle_unmapped_gpa(vp);
 	case HVMSG_GPA_INTERCEPT:
 		return mshv_handle_gpa_intercept(vp);
 	}
@@ -1322,16 +1415,8 @@ static int mshv_prepare_pinned_region(struct mshv_mem_region *region)
 }
 
 /*
- * This maps two things: guest RAM and for pci passthru mmio space.
- *
- * mmio:
- *  - vfio overloads vm_pgoff to store the mmio start pfn/spa.
- *  - Two things need to happen for mapping mmio range:
- *	1. mapped in the uaddr so VMM can access it.
- *	2. mapped in the hwpt (gfn <-> mmio phys addr) so guest can access it.
- *
- *   This function takes care of the second. The first one is managed by vfio,
- *   and hence is taken care of via vfio_pci_mmap_fault().
+ * This is called for both user ram and mmio space. The mmio space is not
+ * mapped here, but later during intercept on demand.
  */
 static long
 mshv_map_user_memory(struct mshv_partition *partition,
@@ -1340,7 +1425,6 @@ mshv_map_user_memory(struct mshv_partition *partition,
 	struct mshv_mem_region *region;
 	struct vm_area_struct *vma;
 	bool is_mmio;
-	ulong mmio_pfn;
 	long ret;
 
 	if (mem->flags & BIT(MSHV_SET_MEM_BIT_UNMAP) ||
@@ -1350,7 +1434,6 @@ mshv_map_user_memory(struct mshv_partition *partition,
 	mmap_read_lock(current->mm);
 	vma = vma_lookup(current->mm, mem->userspace_addr);
 	is_mmio = vma ? !!(vma->vm_flags & (VM_IO | VM_PFNMAP)) : 0;
-	mmio_pfn = is_mmio ? vma->vm_pgoff : 0;
 	mmap_read_unlock(current->mm);
 
 	if (!vma)
@@ -1376,11 +1459,7 @@ mshv_map_user_memory(struct mshv_partition *partition,
 					    region->nr_pages,
 					    HV_MAP_GPA_NO_ACCESS, NULL);
 		break;
-	case MSHV_REGION_TYPE_MMIO:
-		ret = hv_call_map_mmio_pages(partition->pt_id,
-					     region->start_gfn,
-					     mmio_pfn,
-					     region->nr_pages);
+	default:
 		break;
 	}
 
-- 
2.51.2.vfs.0.1

Re: [PATCH V3 10/11] mshv: Populate mmio mappings for PCI passthru

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 5 potential issue(s) to consider:
- [Critical] Unvalidated physical memory mapping and integer overflow allow mapping arbitrary host RAM.
- [Critical] Missing MMU notifier registration and TOCTOU race in MMIO fault handling.
- [High] Architecture page size mismatch corrupts physical address mappings on ARM64.
- [High] Hardcoded write permissions bypass host read-only restrictions for MMIO regions.
- [Medium] Uninitialized stack variable `pfnmap_args`.
--

Note: The format of this report is altered to provide a free-form summary of
the findings, rather than using traditional inline diff quotes, to adhere to
recitation restrictions.

commit f5a60b27c18f019e0a418a3f28dcff85e1128ed4
Author: Mukesh R <mrathor@linux.microsoft.com>
Subject: mshv: Populate mmio mappings for PCI passthru

This commit adds support for mapping mmio memory to the guest upon receiving
an unmapped guest physical address intercept. It looks up the physical frame
number from the driver and asks the hypervisor to establish the map.

While reviewing this code, a few questions came up regarding the handling of
the memory mappings.

When the memory region is created from the user memory structure, it appears
only the start address is validated against the virtual memory area. The page
count is taken directly from user input. Later, in the intercept handler, a
signed 32-bit integer is used to loop over the 64-bit page count. If a user
provides an excessively large size, could the loop counter overflow to a
negative value and prematurely terminate the validation loop? Would this
bypass the ram checks and allow mapping arbitrary host memory into the
guest, while also potentially causing a lockup without a scheduling point?

Is there a race condition when fetching the physical frame number? The memory
map read lock is dropped after resolving the address, and the hypercall is
made without holding it. Since there does not seem to be a memory management
unit interval notifier sequence check here, what happens if the host virtual
memory area is unmapped or modified concurrently? Could the guest retain
access to stale or reallocated host memory?

Does the physical frame number calculation work correctly on architectures
with varying page sizes? On arm64, the kernel page size might be 64KB,
meaning the value returned by the pfnmap functions is based on 64KB units.
However, the handler subtracts a 4KB-based offset from it. Will this
result in an incorrect base physical address being passed to the
hypervisor?

Will this logic handle read-only device memory properly? The code
unconditionally requests a write fault resolution and then hardcodes the
writable flag for the hypervisor map call. If userspace maps a read-only
memory region, will the fault fixup fail? If it does succeed, would the
guest be granted write access to a read-only region?

Does the pfnmap arguments structure need zero-initialization? The structure
is declared on the stack and only the virtual memory area and address
fields are explicitly populated. Could uninitialized padding or other
structure members contain stack garbage that might affect the pfnmap
operations?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260512020259.1678627-1-mrathor@linux.microsoft.com?part=10

[PATCH V3 11/11] mshv: Mark mem regions as non-movable upfront if device passthru

[Mukesh R]

If a VM is started with device attached, the mem regions must be marked
non-movable as the device attach hypercall right away allows the use of
SLAT for IOMMU. Marking them non-movable forces mapping of the entire
guest RAM in the SLAT at the time of region creation along with the
region pinned. Also, because a device could be dynamically attached
much later in a VM, create a boot parameter to disable movable pages
that users can set if they anticipate such an action.

Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
---
 drivers/hv/mshv_root.h      |  1 +
 drivers/hv/mshv_root_main.c | 15 ++++++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/hv/mshv_root.h b/drivers/hv/mshv_root.h
index b9880d0bdc4d..d57c26950203 100644
--- a/drivers/hv/mshv_root.h
+++ b/drivers/hv/mshv_root.h
@@ -141,6 +141,7 @@ struct mshv_partition {
 	pid_t pt_vmm_tgid;
 	bool import_completed;
 	bool pt_initialized;
+	bool pt_regions_pinned;
 #if IS_ENABLED(CONFIG_DEBUG_FS)
 	struct dentry *pt_stats_dentry;
 	struct dentry *pt_vp_dentry;
diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
index a7864463961b..ac71534733bd 100644
--- a/drivers/hv/mshv_root_main.c
+++ b/drivers/hv/mshv_root_main.c
@@ -49,6 +49,10 @@ MODULE_DESCRIPTION("Microsoft Hyper-V root partition VMM interface /dev/mshv");
 static bool hv_nofull_mmio;	/* don't map entire mmio region upon fault */
 module_param(hv_nofull_mmio, bool, 0644);
 
+static bool hv_no_movbl_pgs;	/* disable movable pages completely */
+module_param(hv_no_movbl_pgs, bool, 0644);
+MODULE_PARM_DESC(hv_no_movbl_pgs, "If set, don't do movable pages for VMs");
+
 struct mshv_root mshv_root;
 
 enum hv_scheduler_type hv_scheduler_type;
@@ -1303,6 +1307,12 @@ static void mshv_async_hvcall_handler(void *data, u64 *status)
 	*status = partition->async_hypercall_status;
 }
 
+static bool mshv_do_pt_regions_pinned(struct mshv_partition *pt)
+{
+	return pt->pt_regions_pinned || mshv_partition_encrypted(pt) ||
+	       hv_no_movbl_pgs;
+}
+
 /*
  * NB: caller checks and makes sure mem->size is page aligned
  * Returns: 0 with regionpp updated on success, or -errno
@@ -1333,7 +1343,7 @@ static int mshv_partition_create_region(struct mshv_partition *partition,
 
 	if (is_mmio)
 		rg->mreg_type = MSHV_REGION_TYPE_MMIO;
-	else if (mshv_partition_encrypted(partition) ||
+	else if (mshv_do_pt_regions_pinned(partition) ||
 		 !mshv_region_movable_init(rg))
 		rg->mreg_type = MSHV_REGION_TYPE_MEM_PINNED;
 	else
@@ -1808,6 +1818,9 @@ static long mshv_partition_ioctl_create_device(struct mshv_partition *partition,
 	if (copy_to_user(uarg, &devargk, sizeof(devargk)))
 		return -EFAULT;    /* cleanup in mshv_device_fop_release() */
 
+	/* For now, all regions must be pinned if there is device passthru. */
+	partition->pt_regions_pinned = true;
+
 	return 0;
 
 undo_out:
-- 
2.51.2.vfs.0.1

Re: [PATCH V3 11/11] mshv: Mark mem regions as non-movable upfront if device passthru

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider:
- [Critical] Failing `copy_to_user` during device creation bypasses the `pt_regions_pinned` enforcement while leaving the device fully accessible.
- [High] Device creation does not validate or pin pre-existing memory regions, allowing an unsafe mix of movable regions and device passthrough.
- [High] Missing synchronization between device creation and region creation allows concurrent bypass of the pinning constraint.
--

commit add8cd40c15400cf2b19c8993ce14d4b4a7adef6
Author: Mukesh R <mrathor@linux.microsoft.com>

mshv: Mark mem regions as non-movable upfront if device passthru

This commit ensures that if a VM is started with a device attached, its
memory regions are marked as non-movable upfront to allow the use of SLAT
for IOMMU. It also adds a boot parameter to disable movable pages globally.

> diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
> index a7864463961bc..ac71534733bd8 100644
> --- a/drivers/hv/mshv_root_main.c
> +++ b/drivers/hv/mshv_root_main.c

[ ... ]

> @@ -1303,6 +1307,12 @@ static void mshv_async_hvcall_handler(void *data, u64 *status)
>  	*status = partition->async_hypercall_status;
>  }
>  
> +static bool mshv_do_pt_regions_pinned(struct mshv_partition *pt)
> +{
> +	return pt->pt_regions_pinned || mshv_partition_encrypted(pt) ||
> +	       hv_no_movbl_pgs;
> +}

Is there a potential race condition here between device creation and region
creation?

pt->pt_regions_pinned is written in mshv_partition_ioctl_create_device()
without holding any locks. Concurrently, mshv_partition_create_region()
reads this flag via mshv_do_pt_regions_pinned() without synchronization.

If a region is created while a concurrent device creation thread is about to
set pt_regions_pinned to true, could the region incorrectly be instantiated
as movable while a passthrough device is active?

[ ... ]

> @@ -1808,6 +1818,9 @@ static long mshv_partition_ioctl_create_device(struct mshv_partition *partition,
>  	if (copy_to_user(uarg, &devargk, sizeof(devargk)))
>  		return -EFAULT;    /* cleanup in mshv_device_fop_release() */
>  
> +	/* For now, all regions must be pinned if there is device passthru. */
> +	partition->pt_regions_pinned = true;

If the copy_to_user() fails, the function returns early and skips setting
pt_regions_pinned to true. However, anon_inode_getfd() has already installed
the file descriptor in the process's file descriptor table, meaning the
device remains fully accessible. Can this allow userspace to bypass the
pt_regions_pinned enforcement?

Additionally, when a device is attached, this sets pt_regions_pinned to true
for future memory region creations. Does this handle the case where a
partition already has existing memory regions?

If userspace creates movable regions first and then attaches a device, is
there a risk that page migration could cause the device to DMA into incorrect
physical memory?

>  	return 0;
>  
>  undo_out:

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260512020259.1678627-1-mrathor@linux.microsoft.com?part=11