From 6d2d66bcd31aee39d331d2a8098b6344fd41d8f0 Mon Sep 17 00:00:00 2001
From: Ruben Hakobyan <hruben@meta.com>
Date: Mon, 13 Jul 2026 16:59:42 -0700
Subject: [PATCH] vmm, hypervisor: Make the VMSA page type optional

KVM builds the VMSA internally, so the logic in igvm-loader passing a
VMSA page for KVM is misleading. The page is silently dropped later
in import_isolated_pages(). Only MSHV actually imports it.

Make PageTypeConfig::vmsa an Option that is None on KVM and push the
VMSA page only when it is set. As KVM no longer produces a VMSA page,
remove the now-dead skip in import_isolated_pages().

Signed-off-by: Ruben Hakobyan <hruben@meta.com>
---
 hypervisor/src/kvm/mod.rs        |  5 -----
 hypervisor/src/kvm/x86_64/sev.rs |  2 --
 vmm/src/igvm/igvm_loader.rs      | 23 ++++++++++++-----------
 3 files changed, 12 insertions(+), 18 deletions(-)

diff --git a/hypervisor/src/kvm/mod.rs b/hypervisor/src/kvm/mod.rs
index 5c66aba2f..8a09de5ff 100644
--- a/hypervisor/src/kvm/mod.rs
+++ b/hypervisor/src/kvm/mod.rs
@@ -785,11 +785,6 @@ impl vm::Vm for KvmVm {
             return Ok(());
         }
         assert_eq!(pfns.len(), uaddrs.len());
-        // VMSA pages are not supported by launch_update
-        // https://elixir.bootlin.com/linux/v6.11/source/arch/x86/kvm/svm/sev.c#L2377
-        if page_type == sev::SNP_PAGE_TYPE_VMSA {
-            return Ok(());
-        }
         for i in 0..pfns.len() {
             self.fd
                 .set_memory_attributes(kvm_memory_attributes {
diff --git a/hypervisor/src/kvm/x86_64/sev.rs b/hypervisor/src/kvm/x86_64/sev.rs
index 9c4b621bc..64dddb083 100644
--- a/hypervisor/src/kvm/x86_64/sev.rs
+++ b/hypervisor/src/kvm/x86_64/sev.rs
@@ -23,8 +23,6 @@ const KVM_SEV_INIT2: u32 = 22;
 const KVM_SEV_SNP_LAUNCH_START: u32 = 100;
 const KVM_SEV_SNP_LAUNCH_UPDATE: u32 = 101;
 const KVM_SEV_SNP_LAUNCH_FINISH: u32 = 102;
-// SNP_LAUNCH_UPDATE page types — linux/arch/x86/include/uapi/asm/sev-guest.h
-pub const SNP_PAGE_TYPE_VMSA: u32 = 2;
 
 // See AMD Spec Section 8.17 — SNP_LAUNCH_UPDATE
 // The last 12 bits are metadata about the guest context
diff --git a/vmm/src/igvm/igvm_loader.rs b/vmm/src/igvm/igvm_loader.rs
index a6d9be43d..ae3f4a88d 100644
--- a/vmm/src/igvm/igvm_loader.rs
+++ b/vmm/src/igvm/igvm_loader.rs
@@ -128,8 +128,6 @@ pub enum Error {
 #[cfg(feature = "kvm")]
 const KVM_SNP_PAGE_TYPE_NORMAL: u32 = 1;
 #[cfg(feature = "kvm")]
-const KVM_SNP_PAGE_TYPE_VMSA: u32 = 2;
-#[cfg(feature = "kvm")]
 const KVM_SNP_PAGE_TYPE_ZERO: u32 = 3;
 #[cfg(feature = "kvm")]
 const KVM_SNP_PAGE_TYPE_UNMEASURED: u32 = 4;
@@ -147,7 +145,7 @@ struct PageTypeConfig {
     unmeasured: u32,
     cpuid: u32,
     secrets: u32,
-    vmsa: u32,
+    vmsa: Option<u32>,
 }
 
 #[derive(Copy, Clone)]
@@ -277,7 +275,7 @@ pub fn load_igvm(
     #[cfg(feature = "sev_snp")] host_data: &Option<String>,
 ) -> Result<Box<IgvmLoadedInfo>, Error> {
     let hypervisor_type = cpu_manager.lock().unwrap().hypervisor_type();
-    let page_types = match hypervisor_type {
+    let page_types: PageTypeConfig = match hypervisor_type {
         #[cfg(feature = "mshv")]
         HypervisorType::Mshv => PageTypeConfig {
             isolated_page_size_4kb: mshv_bindings::hv_isolated_page_size_HV_ISOLATED_PAGE_SIZE_4KB,
@@ -286,7 +284,7 @@ pub fn load_igvm(
             unmeasured: mshv_bindings::hv_isolated_page_type_HV_ISOLATED_PAGE_TYPE_UNMEASURED,
             cpuid: mshv_bindings::hv_isolated_page_type_HV_ISOLATED_PAGE_TYPE_CPUID,
             secrets: mshv_bindings::hv_isolated_page_type_HV_ISOLATED_PAGE_TYPE_SECRETS,
-            vmsa: mshv_bindings::hv_isolated_page_type_HV_ISOLATED_PAGE_TYPE_VMSA,
+            vmsa: Some(mshv_bindings::hv_isolated_page_type_HV_ISOLATED_PAGE_TYPE_VMSA),
         },
         #[cfg(feature = "kvm")]
         HypervisorType::Kvm => PageTypeConfig {
@@ -296,7 +294,8 @@ pub fn load_igvm(
             unmeasured: KVM_SNP_PAGE_TYPE_UNMEASURED,
             cpuid: KVM_SNP_PAGE_TYPE_CPUID,
             secrets: KVM_SNP_PAGE_TYPE_SECRETS,
-            vmsa: KVM_SNP_PAGE_TYPE_VMSA,
+            // KVM doesn't import a VMSA page, it instead constructs it internally
+            vmsa: None,
         },
     };
 
@@ -627,11 +626,13 @@ pub fn load_igvm(
                     }
                 }
 
-                gpas.push(GpaPages {
-                    gpa: *gpa,
-                    page_type: page_types.vmsa,
-                    page_size: page_types.isolated_page_size_4kb,
-                });
+                if let Some(vmsa_page_type) = page_types.vmsa {
+                    gpas.push(GpaPages {
+                        gpa: *gpa,
+                        page_type: vmsa_page_type,
+                        page_size: page_types.isolated_page_size_4kb,
+                    });
+                }
             }
             IgvmDirectiveHeader::SnpIdBlock {
                 compatibility_mask,