KVM: MMU: micro-optimize gpte_access

Avoid AND-NOT, most x86 processor lack an instruction for it.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index a1f5459..6013f36 100644 (file)
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -189,8 +189,11 @@ static inline unsigned FNAME(gpte_access)(struct kvm_vcpu *vcpu, u64 gpte)
                ((gpte & VMX_EPT_EXECUTABLE_MASK) ? ACC_EXEC_MASK : 0) |
                ACC_USER_MASK;
 #else
-       access = (gpte & (PT_WRITABLE_MASK | PT_USER_MASK)) | ACC_EXEC_MASK;
-       access &= ~(gpte >> PT64_NX_SHIFT);
+       BUILD_BUG_ON(ACC_EXEC_MASK != PT_PRESENT_MASK);
+       BUILD_BUG_ON(ACC_EXEC_MASK != 1);
+       access = gpte & (PT_WRITABLE_MASK | PT_USER_MASK | PT_PRESENT_MASK);
+       /* Combine NX with P (which is set here) to get ACC_EXEC_MASK.  */
+       access ^= (gpte >> PT64_NX_SHIFT);
 #endif
 
        return access;