RE: [PATCH v2 2/2] KVM: x86/mmu: Micro-optimize nEPT's bad memptype/XWR checks

[David Laight]

From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> Sent: 10 January 2020 16:05
...
> Similar to your suggestion, but it avoids evaluating __is_bad_mt_xwr() if
> reserved bits are set, which is admittedly rare.
> 
> 	return __is_rsvd_bits_set(&mmu->guest_rsvd_check, gpte, level)
> #if PTTYPE == PTTYPE_EPT
> 	       || __is_bad_mt_xwr(&mmu->guest_rsvd_check, gpte)
> #endif
> 	       ;

Or:
	return __is_rsvd_bits_set(&mmu->guest_rsvd_check, gpte, level) ||
		(PTTYPE == PTTYPE_EPT && __is_bad_mt_xwr(&mmu->guest_rsvd_check, gpte));

Relying in the compiler to optimise it away.

	David

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