[Xen-devel] [PATCH v2 1/3] Nested VMX: Check VMX capability before read VMX related MSRs.

[Yang Zhang <yang.z.zhang@xxxxxxxxx>]

From: Yang Zhang <yang.z.zhang@xxxxxxxxx>

VMX MSRs only available when the CPU support the VMX feature. In addition,
VMX_TRUE* MSRs only available when bit 55 of VMX_BASIC MSR is set.

Signed-off-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
---
 xen/arch/x86/hvm/vmx/vvmx.c |   19 +++++++++++++++++++
 1 files changed, 19 insertions(+), 0 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vvmx.c b/xen/arch/x86/hvm/vmx/vvmx.c
index cecc72f..c6c8b88 100644
--- a/xen/arch/x86/hvm/vmx/vvmx.c
+++ b/xen/arch/x86/hvm/vmx/vvmx.c
@@ -1814,12 +1814,31 @@ int nvmx_handle_invvpid(struct cpu_user_regs *regs)
 int nvmx_msr_read_intercept(unsigned int msr, u64 *msr_content)
 {
     struct vcpu *v = current;
+    unsigned int eax, ebx, ecx, edx;
     u64 data = 0, host_data = 0;
     int r = 1;
 
     if ( !nestedhvm_enabled(v->domain) )
         return 0;
 
+    /*
+     * VMX capablitys MSRs available only when guest
+     * support VMX.
+     */
+    hvm_cpuid(0x1, &eax, &ebx, &ecx, &edx);
+    if ( !(ecx & cpufeat_mask(X86_FEATURE_VMXE)) )
+        return 0;
+
+    /*
+     * Those MSRs available only when bit 55 of
+     * MSR_IA32_VMX_BASIC is set.
+     */
+    rdmsrl(MSR_IA32_VMX_BASIC, data);
+    if ( msr >= MSR_IA32_VMX_TRUE_PINBASED_CTLS &&
+         msr <= MSR_IA32_VMX_TRUE_ENTRY_CTLS &&
+         !(data & VMX_BASIC_DEFAULT1_ZERO) )
+        return 0;
+
     rdmsrl(msr, host_data);
 
     /*
-- 
1.7.1


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