[RFC PATCH V3 0/4] x86/Hyper-V: Add AMD Secure AVIC for Hyper-V platform

[RFC PATCH V3 0/4] x86/Hyper-V: Add AMD Secure AVIC for Hyper-V platform

[Tianyu Lan]

From: Tianyu Lan <tiala@microsoft.com>

Secure AVIC is a new hardware feature in the AMD64
architecture to allow SEV-SNP guests to prevent the
hypervisor from generating unexpected interrupts to
a vCPU or otherwise violate architectural assumptions
around APIC behavior.

Each vCPU has a guest-allocated APIC backing page of
size 4K, which maintains APIC state for that vCPU.
APIC backing page's ALLOWED_IRR field indicates the
interrupt vectors which the guest allows the hypervisor
to send.

This patchset is to enable the feature for Hyper-V
platform. Patch "Drivers: hv: Allow vmbus message
synic interrupt injected from Hyper-V" is to expose
new fucntion hv_enable_coco_interrupt() and device
driver and arch code may update AVIC backing page
ALLOWED_IRR field to allow Hyper-V inject associated
vector.

This patchset is based on the AMD patchset "AMD: Add
Secure AVIC Guest Support"
https://lkml.org/lkml/2025/6/10/1579

Change since v2:
       - Add hv_enable_coco_interrupt() as wrapper
        of apic_update_vector()
       - Re-work change logs

Change since v1:
       - Remove the check of Secure AVIC when set APIC backing page
       - Use apic_update_vector() instead of exposing new interface
       from Secure AVIC driver to update APIC backing page and allow
       associated interrupt to be injected by hypervisor.



Tianyu Lan (4):
  x86/Hyper-V: Not use hv apic driver when Secure AVIC is available
  drivers/hv: Allow vmbus message synic interrupt injected from Hyper-V
  x86/Hyper-V: Not use auto-eoi when Secure AVIC is available
  x86/hyperv: Allow Hyper-V to inject STIMER0 interrupts

 arch/x86/hyperv/hv_apic.c      | 8 ++++++++
 arch/x86/hyperv/hv_init.c      | 7 +++++++
 arch/x86/kernel/cpu/mshyperv.c | 2 ++
 drivers/hv/hv.c                | 2 ++
 drivers/hv/hv_common.c         | 5 +++++
 include/asm-generic/mshyperv.h | 1 +
 6 files changed, 25 insertions(+)

-- 
2.25.1

[RFC PATCH V3 1/4] x86/Hyper-V: Not use hv apic driver when Secure AVIC is available

[Tianyu Lan]

From: Tianyu Lan <tiala@microsoft.com>

When Secure AVIC is available, AMD x2apic Secure
AVIC driver should be selected and return directly
in the hv_apic_init().

Signed-off-by: Tianyu Lan <tiala@microsoft.com>
---
 arch/x86/hyperv/hv_apic.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
index bfde0a3498b9..1c48396e5389 100644
--- a/arch/x86/hyperv/hv_apic.c
+++ b/arch/x86/hyperv/hv_apic.c
@@ -293,6 +293,9 @@ static void hv_send_ipi_self(int vector)
 
 void __init hv_apic_init(void)
 {
+       if (cc_platform_has(CC_ATTR_SNP_SECURE_AVIC))
+               return;
+
 	if (ms_hyperv.hints & HV_X64_CLUSTER_IPI_RECOMMENDED) {
 		pr_info("Hyper-V: Using IPI hypercalls\n");
 		/*
-- 
2.25.1

Re: [RFC PATCH V3 1/4] x86/Hyper-V: Not use hv apic driver when Secure AVIC is available

[kernel test robot]

Hi Tianyu,

[This is a private test report for your RFC patch.]
kernel test robot noticed the following build errors:

[auto build test ERROR on tip/x86/core]
[also build test ERROR on tip/master linus/master tip/auto-latest v6.16-rc7 next-20250724]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Tianyu-Lan/x86-Hyper-V-Not-use-hv-apic-driver-when-Secure-AVIC-is-available/20250724-030630
base:   tip/x86/core
patch link:    https://lore.kernel.org/r/20250723190308.5945-2-ltykernel%40gmail.com
patch subject: [RFC PATCH V3 1/4] x86/Hyper-V: Not use hv apic driver when Secure AVIC is available
config: x86_64-buildonly-randconfig-001-20250724 (https://download.01.org/0day-ci/archive/20250724/202507241708.AeqN6zwQ-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14+deb12u1) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250724/202507241708.AeqN6zwQ-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202507241708.AeqN6zwQ-lkp@intel.com/

All errors (new ones prefixed by >>):

   arch/x86/hyperv/hv_apic.c: In function 'hv_apic_init':
>> arch/x86/hyperv/hv_apic.c:296:28: error: 'CC_ATTR_SNP_SECURE_AVIC' undeclared (first use in this function); did you mean 'CC_ATTR_GUEST_SNP_SECURE_TSC'?
     296 |        if (cc_platform_has(CC_ATTR_SNP_SECURE_AVIC))
         |                            ^~~~~~~~~~~~~~~~~~~~~~~
         |                            CC_ATTR_GUEST_SNP_SECURE_TSC
   arch/x86/hyperv/hv_apic.c:296:28: note: each undeclared identifier is reported only once for each function it appears in


vim +296 arch/x86/hyperv/hv_apic.c

   293	
   294	void __init hv_apic_init(void)
   295	{
 > 296	       if (cc_platform_has(CC_ATTR_SNP_SECURE_AVIC))

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

RE: [RFC PATCH V3 1/4] x86/Hyper-V: Not use hv apic driver when Secure AVIC is available

[Michael Kelley]

From: Tianyu Lan <ltykernel@gmail.com> Sent: Wednesday, July 23, 2025 12:03 PM
> 
> When Secure AVIC is available, AMD x2apic Secure
> AVIC driver should be selected and return directly
> in the hv_apic_init().

For the "RFC Patch v2" version of this patch, I had provided some comments
on the wording for the patch "Subject:" and for the commit message. [1] It
doesn't look like those comments were picked up. The comments
improve the use of English without changing any substantive information,
so I think they should be adopted.

[1] https://lore.kernel.org/linux-hyperv/CAMvTesAscN2MyqJXpcbwcXWC-6-en6U_c03M+2=zcMF0bLv4iw@mail.gmail.com/T/#m893e8cac0314e73ee4626d736c623e640b46ef5d

> 
> Signed-off-by: Tianyu Lan <tiala@microsoft.com>
> ---
>  arch/x86/hyperv/hv_apic.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
> index bfde0a3498b9..1c48396e5389 100644
> --- a/arch/x86/hyperv/hv_apic.c
> +++ b/arch/x86/hyperv/hv_apic.c
> @@ -293,6 +293,9 @@ static void hv_send_ipi_self(int vector)
> 
>  void __init hv_apic_init(void)
>  {
> +       if (cc_platform_has(CC_ATTR_SNP_SECURE_AVIC))
> +               return;

This new code is indented with spaces instead of tabs. checkpatch.pl should
flag that.

> +
>  	if (ms_hyperv.hints & HV_X64_CLUSTER_IPI_RECOMMENDED) {
>  		pr_info("Hyper-V: Using IPI hypercalls\n");
>  		/*
> --
> 2.25.1
> 

Re: [RFC PATCH V3 1/4] x86/Hyper-V: Not use hv apic driver when Secure AVIC is available

[Tianyu Lan]

On Fri, Jul 25, 2025 at 7:33 AM Michael Kelley <mhklinux@outlook.com> wrote:
>
> From: Tianyu Lan <ltykernel@gmail.com> Sent: Wednesday, July 23, 2025 12:03 PM
> >
> > When Secure AVIC is available, AMD x2apic Secure
> > AVIC driver should be selected and return directly
> > in the hv_apic_init().
>
> For the "RFC Patch v2" version of this patch, I had provided some comments
> on the wording for the patch "Subject:" and for the commit message. [1] It
> doesn't look like those comments were picked up. The comments
> improve the use of English without changing any substantive information,
> so I think they should be adopted.
>
> [1] https://lore.kernel.org/linux-hyperv/CAMvTesAscN2MyqJXpcbwcXWC-6-en6U_c03M+2=zcMF0bLv4iw@mail.gmail.com/T/#m893e8cac0314e73ee4626d736c623e640b46ef5d
>

Thanks for the reminder. Will update in the next version.

Thanks.

[RFC PATCH V3 2/4] Drivers: hv: Allow vmbus message synic interrupt injected from Hyper-V

[Tianyu Lan]

From: Tianyu Lan <tiala@microsoft.com>

When Secure AVIC is enabled, VMBus driver should
call x2apic Secure AVIC interface to allow Hyper-V
to inject VMBus message interrupt.

Signed-off-by: Tianyu Lan <tiala@microsoft.com>
---
Change since v3
       - Add hv_enable_coco_interrupt() as wrapper
       of apic_update_vector()

 arch/x86/hyperv/hv_apic.c      | 5 +++++
 drivers/hv/hv.c                | 2 ++
 drivers/hv/hv_common.c         | 5 +++++
 include/asm-generic/mshyperv.h | 1 +
 4 files changed, 13 insertions(+)

diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
index 1c48396e5389..dd6829440ea2 100644
--- a/arch/x86/hyperv/hv_apic.c
+++ b/arch/x86/hyperv/hv_apic.c
@@ -53,6 +53,11 @@ static void hv_apic_icr_write(u32 low, u32 id)
 	wrmsrq(HV_X64_MSR_ICR, reg_val);
 }
 
+void hv_enable_coco_interrupt(unsigned int cpu, unsigned int vector, bool set)
+{
+	apic_update_vector(cpu, vector, set);
+}
+
 static u32 hv_apic_read(u32 reg)
 {
 	u32 reg_val, hi;
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 308c8f279df8..2aafe8946e5b 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -20,6 +20,7 @@
 #include <linux/interrupt.h>
 #include <clocksource/hyperv_timer.h>
 #include <asm/mshyperv.h>
+#include <asm/apic.h>
 #include <linux/set_memory.h>
 #include "hyperv_vmbus.h"
 
@@ -310,6 +311,7 @@ void hv_synic_enable_regs(unsigned int cpu)
 	if (vmbus_irq != -1)
 		enable_percpu_irq(vmbus_irq, 0);
 	shared_sint.as_uint64 = hv_get_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT);
+	hv_enable_coco_interrupt(cpu, vmbus_interrupt, true);
 
 	shared_sint.vector = vmbus_interrupt;
 	shared_sint.masked = false;
diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index 49898d10faff..0f024ab3d360 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -716,6 +716,11 @@ u64 __weak hv_tdx_hypercall(u64 control, u64 param1, u64 param2)
 }
 EXPORT_SYMBOL_GPL(hv_tdx_hypercall);
 
+void __weak hv_enable_coco_interrupt(unsigned int cpu, unsigned int vector, bool set)
+{
+}
+EXPORT_SYMBOL_GPL(hv_enable_coco_interrupt);
+
 void hv_identify_partition_type(void)
 {
 	/* Assume guest role */
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index a729b77983fa..7907c9878369 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -333,6 +333,7 @@ bool hv_is_isolation_supported(void);
 bool hv_isolation_type_snp(void);
 u64 hv_ghcb_hypercall(u64 control, void *input, void *output, u32 input_size);
 u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2);
+void hv_enable_coco_interrupt(unsigned int cpu, unsigned int vector, bool set);
 void hyperv_cleanup(void);
 bool hv_query_ext_cap(u64 cap_query);
 void hv_setup_dma_ops(struct device *dev, bool coherent);
-- 
2.25.1

Re: [RFC PATCH V3 2/4] Drivers: hv: Allow vmbus message synic interrupt injected from Hyper-V

[kernel test robot]

Hi Tianyu,

[This is a private test report for your RFC patch.]
kernel test robot noticed the following build errors:

[auto build test ERROR on tip/x86/core]
[also build test ERROR on tip/master linus/master v6.16-rc7 next-20250724]
[cannot apply to tip/auto-latest]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Tianyu-Lan/x86-Hyper-V-Not-use-hv-apic-driver-when-Secure-AVIC-is-available/20250724-030630
base:   tip/x86/core
patch link:    https://lore.kernel.org/r/20250723190308.5945-3-ltykernel%40gmail.com
patch subject: [RFC PATCH V3 2/4] Drivers: hv: Allow vmbus message synic interrupt injected from Hyper-V
config: x86_64-buildonly-randconfig-001-20250724 (https://download.01.org/0day-ci/archive/20250724/202507241811.sZa8qahb-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14+deb12u1) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250724/202507241811.sZa8qahb-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202507241811.sZa8qahb-lkp@intel.com/

All errors (new ones prefixed by >>):

   arch/x86/hyperv/hv_apic.c: In function 'hv_enable_coco_interrupt':
>> arch/x86/hyperv/hv_apic.c:58:9: error: implicit declaration of function 'apic_update_vector'; did you mean 'lapic_update_tsc_freq'? [-Werror=implicit-function-declaration]
      58 |         apic_update_vector(cpu, vector, set);
         |         ^~~~~~~~~~~~~~~~~~
         |         lapic_update_tsc_freq
   arch/x86/hyperv/hv_apic.c: In function 'hv_apic_init':
   arch/x86/hyperv/hv_apic.c:301:28: error: 'CC_ATTR_SNP_SECURE_AVIC' undeclared (first use in this function); did you mean 'CC_ATTR_GUEST_SNP_SECURE_TSC'?
     301 |        if (cc_platform_has(CC_ATTR_SNP_SECURE_AVIC))
         |                            ^~~~~~~~~~~~~~~~~~~~~~~
         |                            CC_ATTR_GUEST_SNP_SECURE_TSC
   arch/x86/hyperv/hv_apic.c:301:28: note: each undeclared identifier is reported only once for each function it appears in
   cc1: some warnings being treated as errors


vim +58 arch/x86/hyperv/hv_apic.c

    55	
    56	void hv_enable_coco_interrupt(unsigned int cpu, unsigned int vector, bool set)
    57	{
  > 58		apic_update_vector(cpu, vector, set);
    59	}
    60	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

RE: [RFC PATCH V3 2/4] Drivers: hv: Allow vmbus message synic interrupt injected from Hyper-V

[Michael Kelley]

From: Tianyu Lan <ltykernel@gmail.com> Sent: Wednesday, July 23, 2025 12:03 PM
> 
> When Secure AVIC is enabled, VMBus driver should
> call x2apic Secure AVIC interface to allow Hyper-V
> to inject VMBus message interrupt.
> 
> Signed-off-by: Tianyu Lan <tiala@microsoft.com>
> ---
> Change since v3
>        - Add hv_enable_coco_interrupt() as wrapper
>        of apic_update_vector()
> 
>  arch/x86/hyperv/hv_apic.c      | 5 +++++
>  drivers/hv/hv.c                | 2 ++
>  drivers/hv/hv_common.c         | 5 +++++
>  include/asm-generic/mshyperv.h | 1 +
>  4 files changed, 13 insertions(+)
> 
> diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
> index 1c48396e5389..dd6829440ea2 100644
> --- a/arch/x86/hyperv/hv_apic.c
> +++ b/arch/x86/hyperv/hv_apic.c
> @@ -53,6 +53,11 @@ static void hv_apic_icr_write(u32 low, u32 id)
>  	wrmsrq(HV_X64_MSR_ICR, reg_val);
>  }
> 
> +void hv_enable_coco_interrupt(unsigned int cpu, unsigned int vector, bool set)
> +{
> +	apic_update_vector(cpu, vector, set);
> +}
> +
>  static u32 hv_apic_read(u32 reg)
>  {
>  	u32 reg_val, hi;
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index 308c8f279df8..2aafe8946e5b 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -20,6 +20,7 @@
>  #include <linux/interrupt.h>
>  #include <clocksource/hyperv_timer.h>
>  #include <asm/mshyperv.h>
> +#include <asm/apic.h>

This #include is no longer needed since apic_update_vector()
isn't being called directly. And the file doesn't exist on arm64,
so it would create a compile error on arm64.

Before submitting, I always do a test compile on arm64 with
my patches so that errors like this are caught beforehand! :-)

>  #include <linux/set_memory.h>
>  #include "hyperv_vmbus.h"
> 
> @@ -310,6 +311,7 @@ void hv_synic_enable_regs(unsigned int cpu)
>  	if (vmbus_irq != -1)
>  		enable_percpu_irq(vmbus_irq, 0);
>  	shared_sint.as_uint64 = hv_get_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT);
> +	hv_enable_coco_interrupt(cpu, vmbus_interrupt, true);

In the "RFC Patch v2" version of this patch, I had asked about whether
the interrupt should be disabled in hv_synic_disable_regs(), so there is
symmetry. [1] I see that in Patch 4 of this series, you are disabling the
STIMER0 interrupt when a CPU goes offline. If disabling vmbus_interrupt
causes a problem, I'm curious about the details.

[1] https://lore.kernel.org/linux-hyperv/CAMvTesAscN2MyqJXpcbwcXWC-6-en6U_c03M+2=zcMF0bLv4iw@mail.gmail.com/T/#m5e7ac9ba9a9b9c9b17dd503291338d21b3c43e7e

> 
>  	shared_sint.vector = vmbus_interrupt;
>  	shared_sint.masked = false;
> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> index 49898d10faff..0f024ab3d360 100644
> --- a/drivers/hv/hv_common.c
> +++ b/drivers/hv/hv_common.c
> @@ -716,6 +716,11 @@ u64 __weak hv_tdx_hypercall(u64 control, u64 param1, u64 param2)
>  }
>  EXPORT_SYMBOL_GPL(hv_tdx_hypercall);
> 
> +void __weak hv_enable_coco_interrupt(unsigned int cpu, unsigned int vector, bool set)
> +{
> +}
> +EXPORT_SYMBOL_GPL(hv_enable_coco_interrupt);
> +
>  void hv_identify_partition_type(void)
>  {
>  	/* Assume guest role */
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index a729b77983fa..7907c9878369 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -333,6 +333,7 @@ bool hv_is_isolation_supported(void);
>  bool hv_isolation_type_snp(void);
>  u64 hv_ghcb_hypercall(u64 control, void *input, void *output, u32 input_size);
>  u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2);
> +void hv_enable_coco_interrupt(unsigned int cpu, unsigned int vector, bool set);
>  void hyperv_cleanup(void);
>  bool hv_query_ext_cap(u64 cap_query);
>  void hv_setup_dma_ops(struct device *dev, bool coherent);
> --
> 2.25.1
> 

Re: [RFC PATCH V3 2/4] Drivers: hv: Allow vmbus message synic interrupt injected from Hyper-V

[Tianyu Lan]

On Fri, Jul 25, 2025 at 7:34 AM Michael Kelley <mhklinux@outlook.com> wrote:
>
> From: Tianyu Lan <ltykernel@gmail.com> Sent: Wednesday, July 23, 2025 12:03 PM
> >
> > When Secure AVIC is enabled, VMBus driver should
> > call x2apic Secure AVIC interface to allow Hyper-V
> > to inject VMBus message interrupt.
> >
> > Signed-off-by: Tianyu Lan <tiala@microsoft.com>
> > ---
> > Change since v3
> >        - Add hv_enable_coco_interrupt() as wrapper
> >        of apic_update_vector()
> >
> >  arch/x86/hyperv/hv_apic.c      | 5 +++++
> >  drivers/hv/hv.c                | 2 ++
> >  drivers/hv/hv_common.c         | 5 +++++
> >  include/asm-generic/mshyperv.h | 1 +
> >  4 files changed, 13 insertions(+)
> >
> > diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
> > index 1c48396e5389..dd6829440ea2 100644
> > --- a/arch/x86/hyperv/hv_apic.c
> > +++ b/arch/x86/hyperv/hv_apic.c
> > @@ -53,6 +53,11 @@ static void hv_apic_icr_write(u32 low, u32 id)
> >       wrmsrq(HV_X64_MSR_ICR, reg_val);
> >  }
> >
> > +void hv_enable_coco_interrupt(unsigned int cpu, unsigned int vector, bool set)
> > +{
> > +     apic_update_vector(cpu, vector, set);
> > +}
> > +
> >  static u32 hv_apic_read(u32 reg)
> >  {
> >       u32 reg_val, hi;
> > diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> > index 308c8f279df8..2aafe8946e5b 100644
> > --- a/drivers/hv/hv.c
> > +++ b/drivers/hv/hv.c
> > @@ -20,6 +20,7 @@
> >  #include <linux/interrupt.h>
> >  #include <clocksource/hyperv_timer.h>
> >  #include <asm/mshyperv.h>
> > +#include <asm/apic.h>
>
> This #include is no longer needed since apic_update_vector()
> isn't being called directly. And the file doesn't exist on arm64,
> so it would create a compile error on arm64.
>
> Before submitting, I always do a test compile on arm64 with
> my patches so that errors like this are caught beforehand! :-)

Yes, good suggestion and will add compilation test on ARM64.
before sending out. Thanks.
>
> >  #include <linux/set_memory.h>
> >  #include "hyperv_vmbus.h"
> >
> > @@ -310,6 +311,7 @@ void hv_synic_enable_regs(unsigned int cpu)
> >       if (vmbus_irq != -1)
> >               enable_percpu_irq(vmbus_irq, 0);
> >       shared_sint.as_uint64 = hv_get_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT);
> > +     hv_enable_coco_interrupt(cpu, vmbus_interrupt, true);
>
> In the "RFC Patch v2" version of this patch, I had asked about whether
> the interrupt should be disabled in hv_synic_disable_regs(), so there is
> symmetry. [1] I see that in Patch 4 of this series, you are disabling the
> STIMER0 interrupt when a CPU goes offline. If disabling vmbus_interrupt
> causes a problem, I'm curious about the details.
>
Yes, that makes sense and will add it.
>
> >
> >       shared_sint.vector = vmbus_interrupt;
> >       shared_sint.masked = false;
> > diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> > index 49898d10faff..0f024ab3d360 100644
> > --- a/drivers/hv/hv_common.c
> > +++ b/drivers/hv/hv_common.c
> > @@ -716,6 +716,11 @@ u64 __weak hv_tdx_hypercall(u64 control, u64 param1, u64 param2)
> >  }
> >  EXPORT_SYMBOL_GPL(hv_tdx_hypercall);
> >
> > +void __weak hv_enable_coco_interrupt(unsigned int cpu, unsigned int vector, bool set)
> > +{
> > +}
> > +EXPORT_SYMBOL_GPL(hv_enable_coco_interrupt);
> > +
> >  void hv_identify_partition_type(void)
> >  {
> >       /* Assume guest role */
> > diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> > index a729b77983fa..7907c9878369 100644
> > --- a/include/asm-generic/mshyperv.h
> > +++ b/include/asm-generic/mshyperv.h
> > @@ -333,6 +333,7 @@ bool hv_is_isolation_supported(void);
> >  bool hv_isolation_type_snp(void);
> >  u64 hv_ghcb_hypercall(u64 control, void *input, void *output, u32 input_size);
> >  u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2);
> > +void hv_enable_coco_interrupt(unsigned int cpu, unsigned int vector, bool set);
> >  void hyperv_cleanup(void);
> >  bool hv_query_ext_cap(u64 cap_query);
> >  void hv_setup_dma_ops(struct device *dev, bool coherent);
> > --
> > 2.25.1
> >
>


-- 
Thanks
Tianyu Lan

[RFC PATCH V3 3/4] x86/Hyper-V: Don't use auto-eoi when Secure AVIC is available

[Tianyu Lan]

From: Tianyu Lan <tiala@microsoft.com>

Hyper-V doesn't support auto-eoi with Secure AVIC.
So set the HV_DEPRECATING_AEOI_RECOMMENDED flag
to force writing the EIO register after handling an interrupt.

Signed-off-by: Tianyu Lan <tiala@microsoft.com>
---
 arch/x86/kernel/cpu/mshyperv.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index c78f860419d6..8f029650f16c 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -463,6 +463,8 @@ static void __init ms_hyperv_init_platform(void)
 		 ms_hyperv.max_vp_index, ms_hyperv.max_lp_index);
 
 	hv_identify_partition_type();
+	if (cc_platform_has(CC_ATTR_SNP_SECURE_AVIC))
+		ms_hyperv.hints |= HV_DEPRECATING_AEOI_RECOMMENDED;
 
 	if (ms_hyperv.hints & HV_X64_HYPERV_NESTED) {
 		hv_nested = true;
-- 
2.25.1

RE: [RFC PATCH V3 3/4] x86/Hyper-V: Don't use auto-eoi when Secure AVIC is available

[Michael Kelley]

From: Tianyu Lan <ltykernel@gmail.com> Sent: Wednesday, July 23, 2025 12:03 PM
> 

I'm nit-picking, but the patch Subject: line prefix should be "x86/hyperv:"
for consistency with past patches. Note that there's no capitalization
or dash. I know not everyone is consistent on this if you look at the git log
for mshyperv.c, but I try to flag it and encourage consistency.

> Hyper-V doesn't support auto-eoi with Secure AVIC.
> So set the HV_DEPRECATING_AEOI_RECOMMENDED flag
> to force writing the EIO register after handling an interrupt.
> 
> Signed-off-by: Tianyu Lan <tiala@microsoft.com>
> ---
>  arch/x86/kernel/cpu/mshyperv.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index c78f860419d6..8f029650f16c 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -463,6 +463,8 @@ static void __init ms_hyperv_init_platform(void)
>  		 ms_hyperv.max_vp_index, ms_hyperv.max_lp_index);
> 
>  	hv_identify_partition_type();
> +	if (cc_platform_has(CC_ATTR_SNP_SECURE_AVIC))
> +		ms_hyperv.hints |= HV_DEPRECATING_AEOI_RECOMMENDED;
> 
>  	if (ms_hyperv.hints & HV_X64_HYPERV_NESTED) {
>  		hv_nested = true;
> --
> 2.25.1
> 

Re: [RFC PATCH V3 3/4] x86/Hyper-V: Don't use auto-eoi when Secure AVIC is available

[Tianyu Lan]

On Fri, Jul 25, 2025 at 7:34 AM Michael Kelley <mhklinux@outlook.com> wrote:
>
> From: Tianyu Lan <ltykernel@gmail.com> Sent: Wednesday, July 23, 2025 12:03 PM
> >
>
> I'm nit-picking, but the patch Subject: line prefix should be "x86/hyperv:"
> for consistency with past patches. Note that there's no capitalization
> or dash. I know not everyone is consistent on this if you look at the git log
> for mshyperv.c, but I try to flag it and encourage consistency.
>
> > Hyper-V doesn't support auto-eoi with Secure AVIC.
> > So set the HV_DEPRECATING_AEOI_RECOMMENDED flag
> > to force writing the EIO register after handling an interrupt.
> >
> > Signed-off-by: Tianyu Lan <tiala@microsoft.com>
> > ---
> >  arch/x86/kernel/cpu/mshyperv.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> > index c78f860419d6..8f029650f16c 100644
> > --- a/arch/x86/kernel/cpu/mshyperv.c
> > +++ b/arch/x86/kernel/cpu/mshyperv.c
> > @@ -463,6 +463,8 @@ static void __init ms_hyperv_init_platform(void)
> >                ms_hyperv.max_vp_index, ms_hyperv.max_lp_index);
> >
> >       hv_identify_partition_type();
> > +     if (cc_platform_has(CC_ATTR_SNP_SECURE_AVIC))
> > +             ms_hyperv.hints |= HV_DEPRECATING_AEOI_RECOMMENDED;
> >
> >       if (ms_hyperv.hints & HV_X64_HYPERV_NESTED) {
> >               hv_nested = true;
> > --
> > 2.25.1
> >
>

Hi Michael:
  Thanks for your review. Will update.
-- 
Thanks
Tianyu Lan

[RFC PATCH V3 4/4] x86/hyperv: Allow Hyper-V to inject STIMER0 interrupts

[Tianyu Lan]

From: Tianyu Lan <tiala@microsoft.com>

When Secure AVIC is enabled, call Secure AVIC
function to allow Hyper-V to inject STIMER0 interrupt.

Signed-off-by: Tianyu Lan <tiala@microsoft.com>
---
 arch/x86/hyperv/hv_init.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 3d1d3547095a..591338162420 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -132,6 +132,10 @@ static int hv_cpu_init(unsigned int cpu)
 		wrmsrq(HV_X64_MSR_VP_ASSIST_PAGE, msr.as_uint64);
 	}
 
+	/* Allow Hyper-V stimer vector to be injected from Hypervisor. */
+	if (ms_hyperv.misc_features & HV_STIMER_DIRECT_MODE_AVAILABLE)
+		apic_update_vector(cpu, HYPERV_STIMER0_VECTOR, true);
+
 	return hyperv_init_ghcb();
 }
 
@@ -239,6 +243,9 @@ static int hv_cpu_die(unsigned int cpu)
 		*ghcb_va = NULL;
 	}
 
+	if (ms_hyperv.misc_features & HV_STIMER_DIRECT_MODE_AVAILABLE)
+		apic_update_vector(cpu, HYPERV_STIMER0_VECTOR, false);
+
 	hv_common_cpu_die(cpu);
 
 	if (hv_vp_assist_page && hv_vp_assist_page[cpu]) {
-- 
2.25.1

RE: [RFC PATCH V3 4/4] x86/hyperv: Allow Hyper-V to inject STIMER0 interrupts

[Michael Kelley]

From: Tianyu Lan <ltykernel@gmail.com> Sent: Wednesday, July 23, 2025 12:03 PM
> 
> When Secure AVIC is enabled, call Secure AVIC
> function to allow Hyper-V to inject STIMER0 interrupt.
> 
> Signed-off-by: Tianyu Lan <tiala@microsoft.com>
> ---
>  arch/x86/hyperv/hv_init.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 3d1d3547095a..591338162420 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -132,6 +132,10 @@ static int hv_cpu_init(unsigned int cpu)
>  		wrmsrq(HV_X64_MSR_VP_ASSIST_PAGE, msr.as_uint64);
>  	}
> 
> +	/* Allow Hyper-V stimer vector to be injected from Hypervisor. */
> +	if (ms_hyperv.misc_features & HV_STIMER_DIRECT_MODE_AVAILABLE)
> +		apic_update_vector(cpu, HYPERV_STIMER0_VECTOR, true);
> +
>  	return hyperv_init_ghcb();
>  }
> 
> @@ -239,6 +243,9 @@ static int hv_cpu_die(unsigned int cpu)
>  		*ghcb_va = NULL;
>  	}
> 
> +	if (ms_hyperv.misc_features & HV_STIMER_DIRECT_MODE_AVAILABLE)
> +		apic_update_vector(cpu, HYPERV_STIMER0_VECTOR, false);
> +
>  	hv_common_cpu_die(cpu);
> 
>  	if (hv_vp_assist_page && hv_vp_assist_page[cpu]) {
> --
> 2.25.1
> 

Reviewed-by: Michael Kelley <mhklinux@outlook.com>