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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>
This commit is contained in:
Paolo Bonzini 2016-02-23 14:19:20 +01:00
parent 6bb69c9b69
commit bb9eadf0c3
1 changed files with 5 additions and 2 deletions
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7
arch/x86/kvm/paging_tmpl.h
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@ -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;