[RFC PATCH] targer/i386: add support for VMX_SECONDARY_EXEC_ENABLE_USER_WAIT_PAUSE

[RFC PATCH] targer/i386: add support for VMX_SECONDARY_EXEC_ENABLE_USER_WAIT_PAUSE

[Ake Koomsin]

Current QEMU can expose waitpkg to guests when it is available. However,
VMX_SECONDARY_EXEC_ENABLE_USER_WAIT_PAUSE is still not recognized and
masked by QEMU. This can lead to an unexpected situation when a L1
hypervisor wants to expose waitpkg to a L2 guest. The L1 hypervisor can
assume that VMX_SECONDARY_EXEC_ENABLE_USER_WAIT_PAUSE exists as waitpkg is
available. The L1 hypervisor then can accidentally expose waitpkg to the
L2 guest. This will cause invalid opcode exception in the L2 guest when
it executes waitpkg related instructions.

This patch adds VMX_SECONDARY_EXEC_ENABLE_USER_WAIT_PAUSE support, and
sets up dependency between the bit and CPUID_7_0_ECX_WAITPKG. QEMU should
not expose waitpkg feature if VMX_SECONDARY_EXEC_ENABLE_USER_WAIT_PAUSE is
not available to avoid unexpected invalid opcode exception in L2 guests.

Signed-off-by: Ake Koomsin <ake@igel.co.jp>
---
 target/i386/cpu.c | 6 +++++-
 target/i386/cpu.h | 1 +
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 97ad229d8b..00f913b638 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -1228,7 +1228,7 @@ FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
             "vmx-invpcid-exit", "vmx-vmfunc", "vmx-shadow-vmcs", "vmx-encls-exit",
             "vmx-rdseed-exit", "vmx-pml", NULL, NULL,
             "vmx-xsaves", NULL, NULL, NULL,
-            NULL, "vmx-tsc-scaling", NULL, NULL,
+            NULL, "vmx-tsc-scaling", "vmx-enable-user-wait-pause", NULL,
             NULL, NULL, NULL, NULL,
         },
         .msr = {
@@ -1545,6 +1545,10 @@ static FeatureDep feature_dependencies[] = {
         .from = { FEAT_8000_0001_ECX,       CPUID_EXT3_SVM },
         .to = { FEAT_SVM,                   ~0ull },
     },
+    {
+        .from = { FEAT_VMX_SECONDARY_CTLS,  VMX_SECONDARY_EXEC_ENABLE_USER_WAIT_PAUSE },
+        .to = { FEAT_7_0_ECX,               CPUID_7_0_ECX_WAITPKG },
+    },
 };
 
 typedef struct X86RegisterInfo32 {
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index e0771a1043..a6000e93bd 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -1111,6 +1111,7 @@ uint64_t x86_cpu_get_supported_feature_word(FeatureWord w,
 #define VMX_SECONDARY_EXEC_ENABLE_PML               0x00020000
 #define VMX_SECONDARY_EXEC_XSAVES                   0x00100000
 #define VMX_SECONDARY_EXEC_TSC_SCALING              0x02000000
+#define VMX_SECONDARY_EXEC_ENABLE_USER_WAIT_PAUSE   0x04000000
 
 #define VMX_PIN_BASED_EXT_INTR_MASK                 0x00000001
 #define VMX_PIN_BASED_NMI_EXITING                   0x00000008
-- 
2.41.0

Re: [RFC PATCH] targer/i386: add support for VMX_SECONDARY_EXEC_ENABLE_USER_WAIT_PAUSE

[Paolo Bonzini]

Queued, thanks.

Paolo