[RFC PATCH V6 0/4] x86/Hyper-V: Add AMD Secure AVIC for Hyper-V platform

[RFC PATCH V6 0/4] x86/Hyper-V: Add AMD Secure AVIC for Hyper-V platform

[Tianyu Lan]

From: Tianyu Lan <tiala@microsoft.com>

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 v5:
       - Rmove extra line and move hv_enable_coco_interrupt()
         just after hv_set_msr() in the hv_synic_disable_regs().
	 
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      | 9 +++++++++
 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, 30 insertions(+), 1 deletion(-)

-- 
2.25.1

[RFC PATCH V6 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>
Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.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 | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
index bfde0a3498b9..01bc02cc0590 100644
--- a/arch/x86/hyperv/hv_apic.c
+++ b/arch/x86/hyperv/hv_apic.c
@@ -25,6 +25,7 @@
 #include <linux/clockchips.h>
 #include <linux/slab.h>
 #include <linux/cpuhotplug.h>
+#include <linux/cc_platform.h>
 #include <asm/hypervisor.h>
 #include <asm/mshyperv.h>
 #include <asm/apic.h>
@@ -293,6 +294,9 @@ 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