drivers: hv: mshv_vtl: Support for Secure AVIC by Brian-Perkins · Pull Request #121 · microsoft/OHCL-Linux-Kernel

Brian-Perkins · 2026-04-16T19:11:46Z

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Copilot

Pull request overview

Adds Secure AVIC (SEV-SNP) support to the Hyper-V VTL (mshv_vtl) path, primarily to accelerate interrupt/IPI handling for hardware-isolated guests and expose required metadata to userspace.

Changes:

Introduces a new MSHV VTL ioctl to retrieve the Secure AVIC backing page PFN for VTL0, and allocates/configures the backing page on SNP.
Refactors/extends in-kernel interrupt offload plumbing (APIC page selection, proxy IRR handling, APICID↔CPUID mapping) to support both TDX and SNP paths.
Updates x86 Hyper-V / SVM related UAPI and headers (new SVM exit codes/flags, VMCB enlightenments structure, Secure AVIC backing page initializer).

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
include/uapi/linux/mshv.h	Adds a new VTL ioctl definition for Secure AVIC PFN retrieval.
include/uapi/hyperv/hvgdk_mini.h	Adds a UAPI definition for Hyper-V VMCB enlightenments.
drivers/hv/mshv_vtl_main.c	Implements Secure AVIC backing page allocation/config and new ioctl; generalizes APIC/proxy-IRR handling for isolated guests.
arch/x86/kernel/apic/x2apic_savic.c	Exposes backing-page initialization helper for Secure AVIC.
arch/x86/include/uapi/asm/svm.h	Adds/aligns SVM exit reason constants used by the new SNP exit handling.
arch/x86/include/asm/svm.h	Adds VMCB flag bits used by SNP exit handling; adjusts Hyper-V header include.
arch/x86/include/asm/sev.h	Adds RMPADJUST permission bit definitions used when configuring Secure AVIC pages.
arch/x86/include/asm/apic.h	Declares the new Secure AVIC backing-page init helper (with stub when unsupported).
arch/x86/hyperv/hv_vtl.c	Disables TSC_ADJUST to skip periodic TSC sync logic under Hyper-V VTL.

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Copilot

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Comments suppressed due to low confidence (1)

arch/x86/kernel/apic/x2apic_savic.c:347

x2apic_savic_init_backing_page() is now a non-static symbol used by drivers/hv/mshv_vtl_main.c, but it is not exported from x2apic_savic.c. Since CONFIG_MSHV_VTL is a tristate (module-capable), building mshv_vtl as a module will fail to link with an undefined symbol unless this function is exported (e.g., EXPORT_SYMBOL_GPL) or the call site is structured to avoid module->vmlinux linkage.

void x2apic_savic_init_backing_page(void *ap)
{
	u32 apic_id;

	/*
	 * Before Secure AVIC is enabled, APIC msr reads are intercepted.
	 * APIC_ID msr read returns the value from the Hypervisor.
	 */
	apic_id = native_apic_msr_read(APIC_ID);
	apic_set_reg(ap, APIC_ID, apic_id);
}

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When Secure AVIC is enabled, call Secure AVIC function to allow Hyper-V to inject STIMER0 interrupt. Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com> Reviewed-by: Michael Kelley <mhklinux@outlook.com> Signed-off-by: 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> Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com> Signed-off-by: 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: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com> Reviewed-by: Michael Kelley <mhklinux@outlook.com> Signed-off-by: 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> Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com> Signed-off-by: Tianyu Lan <tiala@microsoft.com>

Secure AVIC provides backing page to aid the guest in limiting which interrupt vectors can be injected into the guest. Hyper-V has specific hvcall to set backing page and call it in Secure AVIC driver. Signed-off-by: Tianyu Lan <tiala@microsoft.com>

Signed-off-by: Roman Kisel <romank@linux.microsoft.com> Signed-off-by: Tianyu Lan <tiala@microsoft.com>

Copilot

Pull request overview

Copilot reviewed 16 out of 16 changed files in this pull request and generated 5 comments.

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Copilot · 2026-04-28T01:12:52Z

@@ -361,7 +376,11 @@ static void savic_setup(void)
 	 * VMRUN, the hypervisor makes use of this information to make sure
 	 * the APIC backing page is mapped in NPT.
 	 */
-	res = savic_register_gpa(gpa);
+	if (hv_isolation_type_snp())
+		ret = hv_set_savic_backing_page(gfn);
+	else
+		ret = savic_register_gpa(gpa);
+
 	if (res != ES_OK)
 		sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_SAVIC_FAIL);


In savic_setup(), enum es_result res is never assigned after switching to ret = hv_set_savic_backing_page() / ret = savic_register_gpa(), but the code still checks if (res != ES_OK). This leaves res uninitialized and will trigger incorrect termination; also the return types now mismatch (hv_set_savic_backing_page returns enum es_result). Use a single enum es_result res result variable and assign/check it consistently (or update the check to use ret and convert types appropriately).

Copilot · 2026-04-28T01:12:52Z

+	if (cc_platform_has(CC_ATTR_SNP_SECURE_AVIC)) {
+		hv_vp_early_input_arg = kcalloc(num_possible_cpus(),
+					     PAGE_SIZE,
+					     GFP_KERNEL);
+		if (hv_vp_early_input_arg) {
+			ret = set_memory_decrypted((u64)hv_vp_early_input_arg,
+					     num_possible_cpus());
+			if (ret) {
+				kfree(hv_vp_early_input_arg);
+				goto common_free;
+			}
+		} else {
+			goto common_free;
+		}


hv_vp_early_input_arg is allocated with kcalloc() and then passed to set_memory_decrypted(). set_memory_decrypted() warns and rounds down misaligned addresses, so this needs a PAGE_SIZE-aligned allocation to avoid converting the wrong pages. Consider allocating with a page-aligned API (e.g., __get_free_pages()/alloc_pages_exact()) rather than kcalloc().

Copilot · 2026-04-28T01:12:53Z

 	kfree(hv_vp_assist_page);
 	hv_vp_assist_page = NULL;
+free_vp_early_input_arg:
+	set_memory_encrypted((u64)hv_vp_early_input_arg, num_possible_cpus());


The free_vp_early_input_arg: error path unconditionally calls set_memory_encrypted() on hv_vp_early_input_arg. If Secure AVIC isn’t enabled (or allocation failed before setting the pointer), this can end up converting address 0 / a NULL pointer. Guard the conversion with if (hv_vp_early_input_arg) (and only attempt set_memory_encrypted() when it was successfully decrypted earlier).

Suggested change

set_memory_encrypted((u64)hv_vp_early_input_arg, num_possible_cpus());

if (hv_vp_early_input_arg)

set_memory_encrypted((u64)hv_vp_early_input_arg,

num_possible_cpus());

Copilot · 2026-04-28T01:12:53Z

+	struct hv_set_vp_registers_input *input
+		= hv_vp_early_input_arg + smp_processor_id() * PAGE_SIZE;


hv_set_savic_backing_page() does pointer arithmetic on hv_vp_early_input_arg even though it’s declared as void * (hv_vp_early_input_arg + smp_processor_id() * PAGE_SIZE). This trips -Wpointer-arith on Clang/GCC and is non-standard C. Cast to a byte pointer for the arithmetic (or change the global’s type to u8 *) before adding the per-CPU offset.

Suggested change

struct hv_set_vp_registers_input *input

= hv_vp_early_input_arg + smp_processor_id() * PAGE_SIZE;

struct hv_set_vp_registers_input *input =

(struct hv_set_vp_registers_input *)

((u8 *)hv_vp_early_input_arg + smp_processor_id() * PAGE_SIZE);

Copilot · 2026-04-28T01:12:53Z

+ */
+#define		HV_X64_REGISTER_VSM_VP_STATUS   0x000D0003
+#define		HV_X64_VTL_MASK                 GENMASK(3, 0)
+#define		HV_X64_REGISTER_SEV_AVIC_GPA    0x00090043


These new #define constants are duplicates of ones already provided via <hyperv/hvhdk.h> → hvgdk_mini.h (e.g., HV_X64_REGISTER_VSM_VP_STATUS / HV_X64_VTL_MASK). Because this header includes hvhdk.h before these #defines, this can trigger macro redefinition warnings (notably with Clang). Prefer to define them in only one place, or wrap with #ifndef guards here.

Suggested change

*/

#define HV_X64_REGISTER_VSM_VP_STATUS 0x000D0003

#define HV_X64_VTL_MASK GENMASK(3, 0)

#define HV_X64_REGISTER_SEV_AVIC_GPA 0x00090043

*/

#ifndef HV_X64_REGISTER_VSM_VP_STATUS

#define HV_X64_REGISTER_VSM_VP_STATUS 0x000D0003

#endif

#ifndef HV_X64_VTL_MASK

#define HV_X64_VTL_MASK GENMASK(3, 0)

#endif

#ifndef HV_X64_REGISTER_SEV_AVIC_GPA

#define HV_X64_REGISTER_SEV_AVIC_GPA 0x00090043

#endif

Brian-Perkins requested review from Copilot, hargar19 and tiala April 16, 2026 19:11

Copilot started reviewing on behalf of Brian-Perkins April 16, 2026 19:13 View session

Copilot AI reviewed Apr 16, 2026

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Comment thread drivers/hv/mshv_vtl_main.c

Comment thread drivers/hv/mshv_vtl_main.c

Comment thread drivers/hv/mshv_vtl_main.c Outdated

Comment thread include/uapi/linux/mshv.h

Comment thread arch/x86/include/asm/svm.h Outdated

Comment thread include/uapi/hyperv/hvgdk_mini.h Outdated

Brian-Perkins force-pushed the snp_savic branch from 579837a to c323ace Compare April 16, 2026 20:48

Copilot AI review requested due to automatic review settings April 16, 2026 22:22

Brian-Perkins force-pushed the snp_savic branch from c323ace to 3331547 Compare April 16, 2026 22:22

Copilot started reviewing on behalf of Brian-Perkins April 16, 2026 22:24 View session

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Comment thread drivers/hv/mshv_vtl_main.c

Comment thread drivers/hv/mshv_vtl_main.c Outdated

Brian-Perkins force-pushed the snp_savic branch from 3331547 to 78fa247 Compare April 16, 2026 23:58

Brian-Perkins changed the base branch from product/hcl-main/6.12 to product/hcl-main/6.18 April 21, 2026 23:06

Brian-Perkins force-pushed the snp_savic branch from 78fa247 to 44270f4 Compare April 22, 2026 00:58

tiala and others added 6 commits April 27, 2026 23:37

drivers: hv: mshv_vtl: Support for Secure AVIC

0955f99

Signed-off-by: Roman Kisel <romank@linux.microsoft.com> Signed-off-by: Tianyu Lan <tiala@microsoft.com>

Copilot AI review requested due to automatic review settings April 28, 2026 01:04

Brian-Perkins force-pushed the snp_savic branch from 44270f4 to 0955f99 Compare April 28, 2026 01:04

Copilot started reviewing on behalf of Brian-Perkins April 28, 2026 01:06 View session

Copilot AI reviewed Apr 28, 2026

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Fix copilot PR suggestions

aab4c1e

saurabh-sengar deleted the branch microsoft:product/hcl-main/6.18 April 28, 2026 06:06

saurabh-sengar closed this Apr 28, 2026

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drivers: hv: mshv_vtl: Support for Secure AVIC#121

drivers: hv: mshv_vtl: Support for Secure AVIC#121
Brian-Perkins wants to merge 7 commits intomicrosoft:product/hcl-main/6.18from
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		struct hv_set_vp_registers_input *input
		= hv_vp_early_input_arg + smp_processor_id() * PAGE_SIZE;

-	struct hv_set_vp_registers_input *input
-		= hv_vp_early_input_arg + smp_processor_id() * PAGE_SIZE;
+	struct hv_set_vp_registers_input *input =
+		(struct hv_set_vp_registers_input *)
+		((u8 *)hv_vp_early_input_arg + smp_processor_id() * PAGE_SIZE);

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