[RFC PATCH V5 0/4] x86/Hyper-V: Add AMD Secure AVIC for Hyper-V platform

[RFC PATCH V5 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 v4:
        - Change the order to call hv_enable_coco_interrupt()
	  in the hv_synic_enable/disable_regs().
	- Update commit title "Drivers/hv:" to "Drivers: hv:"

Change since v3:
        - Disable VMBus Message interrupt via hv_enable_
          coco_interrupt() in the hv_synic_disable_regs().
        - Fix coding style issue and update change log.

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/hyperv: Don't use hv apic driver when Secure AVIC is available
  Drivers: hv: Allow vmbus message synic interrupt injected from Hyper-V
  x86/hyperv: Don't 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                | 7 ++++++-
 drivers/hv/hv_common.c         | 5 +++++
 include/asm-generic/mshyperv.h | 1 +
 6 files changed, 29 insertions(+), 1 deletion(-)

-- 
2.25.1

[RFC PATCH V5 1/4] x86/hyperv: Don't use hv apic driver when Secure AVIC is available

[Tianyu Lan]

From: Tianyu Lan <tiala@microsoft.com>

When Secure AVIC is available, the AMD x2apic Secure
AVIC driver will be selected. In that case, have hv_apic_init()
return immediately without doing anything.

Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Tianyu Lan <tiala@microsoft.com>
---
Change since RFC V3:
       - Update Change log and fix coding style issue.
---
 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..e669053b637d 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 V5 1/4] x86/hyperv: Don't use hv apic driver when Secure AVIC is available

[Neeraj Upadhyay]

On 8/4/2025 11:35 PM, Tianyu Lan wrote:
> From: Tianyu Lan <tiala@microsoft.com>
> 
> When Secure AVIC is available, the AMD x2apic Secure
> AVIC driver will be selected. In that case, have hv_apic_init()
> return immediately without doing anything.
> 
> Reviewed-by: Michael Kelley <mhklinux@outlook.com>
> Signed-off-by: Tianyu Lan <tiala@microsoft.com>
> ---


Do you need to include linux/cc_platform.h ?

Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>


- Neeraj

[RFC PATCH V5 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.

Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Tianyu Lan <tiala@microsoft.com>
---
Change since RFC V4:
        - Change the order to call hv_enable_coco_interrupt()
	  in the hv_synic_enable/disable_regs().
	- Update commit title "Drivers/hv:" to "Drivers: hv:"

Change since RFC V3:
       - Disable VMBus Message interrupt via hv_enable_
       	 coco_interrupt() in the hv_synic_disable_regs().
---
 arch/x86/hyperv/hv_apic.c      | 5 +++++
 drivers/hv/hv.c                | 7 ++++++-
 drivers/hv/hv_common.c         | 5 +++++
 include/asm-generic/mshyperv.h | 1 +
 4 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
index e669053b637d..a8de503def37 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..2ff433cb5cc2 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -314,8 +314,11 @@ void hv_synic_enable_regs(unsigned int cpu)
 	shared_sint.vector = vmbus_interrupt;
 	shared_sint.masked = false;
 	shared_sint.auto_eoi = hv_recommend_using_aeoi();
+
 	hv_set_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT, shared_sint.as_uint64);
 
+	hv_enable_coco_interrupt(cpu, vmbus_interrupt, true);
+
 	/* Enable the global synic bit */
 	sctrl.as_uint64 = hv_get_msr(HV_MSR_SCONTROL);
 	sctrl.enable = 1;
@@ -342,7 +345,6 @@ void hv_synic_disable_regs(unsigned int cpu)
 	union hv_synic_scontrol sctrl;
 
 	shared_sint.as_uint64 = hv_get_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT);
-
 	shared_sint.masked = 1;
 
 	/* Need to correctly cleanup in the case of SMP!!! */
@@ -350,6 +352,9 @@ void hv_synic_disable_regs(unsigned int cpu)
 	hv_set_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT, shared_sint.as_uint64);
 
 	simp.as_uint64 = hv_get_msr(HV_MSR_SIMP);
+
+	hv_enable_coco_interrupt(cpu, vmbus_interrupt, false);
+
 	/*
 	 * In Isolation VM, sim and sief pages are allocated by
 	 * paravisor. These pages also will be used by kdump
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 V5 2/4] Drivers: hv: Allow vmbus message synic interrupt injected from Hyper-V

[Neeraj Upadhyay]

On 8/4/2025 11:35 PM, Tianyu Lan wrote:
> From: Tianyu Lan <tiala@microsoft.com>
> 

...

> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index 308c8f279df8..2ff433cb5cc2 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -314,8 +314,11 @@ void hv_synic_enable_regs(unsigned int cpu)
>  	shared_sint.vector = vmbus_interrupt;
>  	shared_sint.masked = false;
>  	shared_sint.auto_eoi = hv_recommend_using_aeoi();
> +

Nit: extra newline.

>  	hv_set_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT, shared_sint.as_uint64);
>  
> +	hv_enable_coco_interrupt(cpu, vmbus_interrupt, true);
> +
>  	/* Enable the global synic bit */
>  	sctrl.as_uint64 = hv_get_msr(HV_MSR_SCONTROL);
>  	sctrl.enable = 1;
> @@ -342,7 +345,6 @@ void hv_synic_disable_regs(unsigned int cpu)
>  	union hv_synic_scontrol sctrl;
>  
>  	shared_sint.as_uint64 = hv_get_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT);
> -

Nit: extra newline.


>  	shared_sint.masked = 1;
>  
>  	/* Need to correctly cleanup in the case of SMP!!! */
> @@ -350,6 +352,9 @@ void hv_synic_disable_regs(unsigned int cpu)
>  	hv_set_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT, shared_sint.as_uint64);
>  
>  	simp.as_uint64 = hv_get_msr(HV_MSR_SIMP);
> +
> +	hv_enable_coco_interrupt(cpu, vmbus_interrupt, false);
> +

Nit: Maybe this should be above "simp.as_uint64 = hv_get_msr(HV_MSR_SIMP)" ?

Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>


- Neeraj

Re: [RFC PATCH V5 2/4] Drivers: hv: Allow vmbus message synic interrupt injected from Hyper-V

[Tianyu Lan]

On Tue, Aug 5, 2025 at 9:59 PM Neeraj Upadhyay <Neeraj.Upadhyay@amd.com> wrote:
>
>
>
> On 8/4/2025 11:35 PM, Tianyu Lan wrote:
> > From: Tianyu Lan <tiala@microsoft.com>
> >
> > diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> > index 308c8f279df8..2ff433cb5cc2 100644
> > --- a/drivers/hv/hv.c
> > +++ b/drivers/hv/hv.c
> > @@ -314,8 +314,11 @@ void hv_synic_enable_regs(unsigned int cpu)
> >       shared_sint.vector = vmbus_interrupt;
> >       shared_sint.masked = false;
> >       shared_sint.auto_eoi = hv_recommend_using_aeoi();
> > +
>
> Nit: extra newline.

Thanks for your review. Will remove it..

>
> >       hv_set_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT, shared_sint.as_uint64);
> >
> > +     hv_enable_coco_interrupt(cpu, vmbus_interrupt, true);
> > +
> >       /* Enable the global synic bit */
> >       sctrl.as_uint64 = hv_get_msr(HV_MSR_SCONTROL);
> >       sctrl.enable = 1;
> > @@ -342,7 +345,6 @@ void hv_synic_disable_regs(unsigned int cpu)
> >       union hv_synic_scontrol sctrl;
> >
> >       shared_sint.as_uint64 = hv_get_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT);
> > -
>
> Nit: extra newline.
>

Will remove it..


>
> >       shared_sint.masked = 1;
> >
> >       /* Need to correctly cleanup in the case of SMP!!! */
> > @@ -350,6 +352,9 @@ void hv_synic_disable_regs(unsigned int cpu)
> >       hv_set_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT, shared_sint.as_uint64);
> >
> >       simp.as_uint64 = hv_get_msr(HV_MSR_SIMP);
> > +
> > +     hv_enable_coco_interrupt(cpu, vmbus_interrupt, false);
> > +
>
> Nit: Maybe this should be above "simp.as_uint64 = hv_get_msr(HV_MSR_SIMP)" ?
>



--
Thanks
Tianyu Lan

RE: [RFC PATCH V5 2/4] Drivers: hv: Allow vmbus message synic interrupt injected from Hyper-V

[Michael Kelley]

From: Tianyu Lan <ltykernel@gmail.com> Sent: Monday, August 4, 2025 11:05 AM
> 
> When Secure AVIC is enabled, VMBus driver should
> call x2apic Secure AVIC interface to allow Hyper-V
> to inject VMBus message interrupt.
> 
> Reviewed-by: Michael Kelley <mhklinux@outlook.com>
> Signed-off-by: Tianyu Lan <tiala@microsoft.com>
> ---
> Change since RFC V4:
>         - Change the order to call hv_enable_coco_interrupt()
> 	  in the hv_synic_enable/disable_regs().
> 	- Update commit title "Drivers/hv:" to "Drivers: hv:"
> 
> Change since RFC V3:
>        - Disable VMBus Message interrupt via hv_enable_
>        	 coco_interrupt() in the hv_synic_disable_regs().
> ---
>  arch/x86/hyperv/hv_apic.c      | 5 +++++
>  drivers/hv/hv.c                | 7 ++++++-
>  drivers/hv/hv_common.c         | 5 +++++
>  include/asm-generic/mshyperv.h | 1 +
>  4 files changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
> index e669053b637d..a8de503def37 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..2ff433cb5cc2 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -314,8 +314,11 @@ void hv_synic_enable_regs(unsigned int cpu)
>  	shared_sint.vector = vmbus_interrupt;
>  	shared_sint.masked = false;
>  	shared_sint.auto_eoi = hv_recommend_using_aeoi();
> +
>  	hv_set_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT, shared_sint.as_uint64);
> 
> +	hv_enable_coco_interrupt(cpu, vmbus_interrupt, true);
> +
>  	/* Enable the global synic bit */
>  	sctrl.as_uint64 = hv_get_msr(HV_MSR_SCONTROL);
>  	sctrl.enable = 1;
> @@ -342,7 +345,6 @@ void hv_synic_disable_regs(unsigned int cpu)
>  	union hv_synic_scontrol sctrl;
> 
>  	shared_sint.as_uint64 = hv_get_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT);
> -
>  	shared_sint.masked = 1;
> 
>  	/* Need to correctly cleanup in the case of SMP!!! */
> @@ -350,6 +352,9 @@ void hv_synic_disable_regs(unsigned int cpu)
>  	hv_set_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT, shared_sint.as_uint64);
> 
>  	simp.as_uint64 = hv_get_msr(HV_MSR_SIMP);
> +
> +	hv_enable_coco_interrupt(cpu, vmbus_interrupt, false);
> +

I agree with Neeraj's comment on the placement of this line of code.
As I commented on v4 of the series, the hv_synic_enable/disable_regs()
functions have units of code that do read, modify, then write of a
synthetic MSR, such as the SIMP, SIEFP, and SINT. It's weird to have
hv_enable_coco_interrupt() in the middle of such a unit. In this v5,
you fixed the issue for hv_synic_enable_regs(), but not here for
hv_synic_disable_regs(). The call to hv_enable_coco_interrupt()
should go after call to hv_set_msr(HV_MSR_SINT0 ....), but before
the call to hv_get_msr(HV_MSR_SIMP) so that the read/modify/write
units aren't mixed with other things.

Michael

>  	/*
>  	 * In Isolation VM, sim and sief pages are allocated by
>  	 * paravisor. These pages also will be used by kdump
> 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 V5 2/4] Drivers: hv: Allow vmbus message synic interrupt injected from Hyper-V

[Tianyu Lan]

On Wed, Aug 6, 2025 at 2:09 AM Michael Kelley <mhklinux@outlook.com> wrote:
>
> From: Tianyu Lan <ltykernel@gmail.com> Sent: Monday, August 4, 2025 11:05 AM
> >
> > When Secure AVIC is enabled, VMBus driver should
> > call x2apic Secure AVIC interface to allow Hyper-V
> > to inject VMBus message interrupt.
> >
> > Reviewed-by: Michael Kelley <mhklinux@outlook.com>
> > Signed-off-by: Tianyu Lan <tiala@microsoft.com>
> > ---
> > Change since RFC V4:
> >         - Change the order to call hv_enable_coco_interrupt()
> >         in the hv_synic_enable/disable_regs().
> >       - Update commit title "Drivers/hv:" to "Drivers: hv:"
> >
> > Change since RFC V3:
> >        - Disable VMBus Message interrupt via hv_enable_
> >                coco_interrupt() in the hv_synic_disable_regs().
> > ---
> >  arch/x86/hyperv/hv_apic.c      | 5 +++++
> >  drivers/hv/hv.c                | 7 ++++++-
> >  drivers/hv/hv_common.c         | 5 +++++
> >  include/asm-generic/mshyperv.h | 1 +
> >  4 files changed, 17 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
> > index e669053b637d..a8de503def37 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..2ff433cb5cc2 100644
> > --- a/drivers/hv/hv.c
> > +++ b/drivers/hv/hv.c
> > @@ -314,8 +314,11 @@ void hv_synic_enable_regs(unsigned int cpu)
> >       shared_sint.vector = vmbus_interrupt;
> >       shared_sint.masked = false;
> >       shared_sint.auto_eoi = hv_recommend_using_aeoi();
> > +
> >       hv_set_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT, shared_sint.as_uint64);
> >
> > +     hv_enable_coco_interrupt(cpu, vmbus_interrupt, true);
> > +
> >       /* Enable the global synic bit */
> >       sctrl.as_uint64 = hv_get_msr(HV_MSR_SCONTROL);
> >       sctrl.enable = 1;
> > @@ -342,7 +345,6 @@ void hv_synic_disable_regs(unsigned int cpu)
> >       union hv_synic_scontrol sctrl;
> >
> >       shared_sint.as_uint64 = hv_get_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT);
> > -
> >       shared_sint.masked = 1;
> >
> >       /* Need to correctly cleanup in the case of SMP!!! */
> > @@ -350,6 +352,9 @@ void hv_synic_disable_regs(unsigned int cpu)
> >       hv_set_msr(HV_MSR_SINT0 + VMBUS_MESSAGE_SINT, shared_sint.as_uint64);
> >
> >       simp.as_uint64 = hv_get_msr(HV_MSR_SIMP);
> > +
> > +     hv_enable_coco_interrupt(cpu, vmbus_interrupt, false);
> > +
>
> I agree with Neeraj's comment on the placement of this line of code.
> As I commented on v4 of the series, the hv_synic_enable/disable_regs()
> functions have units of code that do read, modify, then write of a
> synthetic MSR, such as the SIMP, SIEFP, and SINT. It's weird to have
> hv_enable_coco_interrupt() in the middle of such a unit. In this v5,
> you fixed the issue for hv_synic_enable_regs(), but not here for
> hv_synic_disable_regs(). The call to hv_enable_coco_interrupt()
> should go after call to hv_set_msr(HV_MSR_SINT0 ....), but before
> the call to hv_get_msr(HV_MSR_SIMP) so that the read/modify/write
> units aren't mixed with other things.
>
Hi Michael:
       Thanks for your review. Agree. Will update in the next version.

--
Thanks
Tianyu Lan

[RFC PATCH V5 3/4] x86/hyperv: 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 EOI register after handling an interrupt.

Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Tianyu Lan <tiala@microsoft.com>
---
Change since RFC V3:
       - Update title prefix from "x86/Hyper-V" to "x86/hyperv"
---
 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 V5 3/4] x86/hyperv: Don't use auto-eoi when Secure AVIC is available

[Neeraj Upadhyay]

On 8/4/2025 11:35 PM, Tianyu Lan wrote:
> 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 EOI register after handling an interrupt.
> 
> Reviewed-by: Michael Kelley <mhklinux@outlook.com>
> Signed-off-by: Tianyu Lan <tiala@microsoft.com>
> ---
> Change since RFC V3:
>        - Update title prefix from "x86/Hyper-V" to "x86/hyperv"
> ---

Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>

[RFC PATCH V5 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.

Reviewed-by: Michael Kelley <mhklinux@outlook.com>
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 V5 4/4] x86/hyperv: Allow Hyper-V to inject STIMER0 interrupts

[Neeraj Upadhyay]

On 8/4/2025 11:35 PM, Tianyu Lan wrote:
> From: Tianyu Lan <tiala@microsoft.com>
> 
> When Secure AVIC is enabled, call Secure AVIC
> function to allow Hyper-V to inject STIMER0 interrupt.
> 
> Reviewed-by: Michael Kelley <mhklinux@outlook.com>
> Signed-off-by: Tianyu Lan <tiala@microsoft.com>
> ---

Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>

Re: [RFC PATCH V5 0/4] x86/Hyper-V: Add AMD Secure AVIC for Hyper-V platform

[Naman Jain]

On 8/4/2025 11:35 PM, Tianyu Lan wrote:
> 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"
> 


NIT:
Generally RFC tag is meant to be used for the patches which are probably 
not ready for merging, and is mostly intended for having a discussion 
around your changes. Since this is now reviewed by multiple people and 
have gone through multiple versions already, if you feel this can be 
merged, you can remove RFC tags in next version, if you are planning to 
send it.

Regards,
Naman

Re: [RFC PATCH V5 0/4] x86/Hyper-V: Add AMD Secure AVIC for Hyper-V platform

[Tianyu Lan]

On Wed, Aug 6, 2025 at 1:42 PM Naman Jain <namjain@linux.microsoft.com> wrote:
>
>
>
> On 8/4/2025 11:35 PM, Tianyu Lan wrote:
> > 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"
> >
>
>
> NIT:
> Generally RFC tag is meant to be used for the patches which are probably
> not ready for merging, and is mostly intended for having a discussion
> around your changes. Since this is now reviewed by multiple people and
> have gone through multiple versions already, if you feel this can be
> merged, you can remove RFC tags in next version, if you are planning to
> send it.
>
Hi Naman:
     Thanks for your review and suggestion. This patchset is based on
the AMD Secure AVIC
driver patchset.which is still with RFC tag. I will remove the RFC tag
of this patchset after AMD
patchset merged.
.
...
Thanks
Tianyu Lan