KVM: MMU: micro-optimize gpte_access

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

Paolo Bonzini committed 10 years ago

Commit bb9eadf1 parent 6bb69c91 file · +5 −2Browse files

Unified · Split

arch/x86/kvm/paging_tmpl.h+5−2

@@ -189,8 +189,11 @@ static inline unsigned FNAME(gpte_access)(struct kvm_vcpu *vcpu, u64 gpte) · 188 unmodified lines
189	189	((gpte & VMX_EPT_EXECUTABLE_MASK) ? ACC_EXEC_MASK : 0) \|
190	190	ACC_USER_MASK;
191	191	#else
192		− access = (gpte & (PT_WRITABLE_MASK \| PT_USER_MASK)) \| ACC_EXEC_MASK;
193		− access &= ~(gpte >> PT64_NX_SHIFT);
	192	+ BUILD_BUG_ON(ACC_EXEC_MASK != PT_PRESENT_MASK);
	193	+ BUILD_BUG_ON(ACC_EXEC_MASK != 1);
	194	+ access = gpte & (PT_WRITABLE_MASK \| PT_USER_MASK \| PT_PRESENT_MASK);
	195	+ /* Combine NX with P (which is set here) to get ACC_EXEC_MASK. */
	196	+ access ^= (gpte >> PT64_NX_SHIFT);
194	197	#endif
195	198
196	199	return access;