[Xen-devel] [PATCH v3] x86/vmx: correct the SMEP logic for HVM_CR0_GUEST_RESERVED_BITS

[Feng Wu <feng.wu@xxxxxxxxx>]

When checking the SMEP feature for HVM guests, we should check the
VCPU instead of the host CPU.

Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/include/asm-x86/hvm/hvm.h | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
index dcc3483..a1f639c 100644
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -351,6 +351,19 @@ static inline int hvm_event_pending(struct vcpu *v)
     return hvm_funcs.event_pending(v);
 }
 
+static inline bool_t hvm_vcpu_has_smep(void)
+{
+    unsigned int eax, ebx;
+
+    hvm_cpuid(0x0, &eax, NULL, NULL, NULL);
+
+    if ( eax < 0x7 )
+        return 0;
+
+    hvm_cpuid(0x7, NULL, &ebx, NULL, NULL);
+    return !!(ebx & cpufeat_mask(X86_FEATURE_SMEP));
+}
+
 /* These reserved bits in lower 32 remain 0 after any load of CR0 */
 #define HVM_CR0_GUEST_RESERVED_BITS             \
     (~((unsigned long)                          \
@@ -370,7 +383,7 @@ static inline int hvm_event_pending(struct vcpu *v)
         X86_CR4_DE  | X86_CR4_PSE | X86_CR4_PAE |       \
         X86_CR4_MCE | X86_CR4_PGE | X86_CR4_PCE |       \
         X86_CR4_OSFXSR | X86_CR4_OSXMMEXCPT |           \
-        (cpu_has_smep ? X86_CR4_SMEP : 0) |             \
+        (hvm_vcpu_has_smep() ? X86_CR4_SMEP : 0) |      \
         (cpu_has_fsgsbase ? X86_CR4_FSGSBASE : 0) |     \
         ((nestedhvm_enabled((_v)->domain) && cpu_has_vmx)\
                       ? X86_CR4_VMXE : 0)  |             \
-- 
1.8.3.1


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