Commit e40bcf9f authored by Mathias Krause's avatar Mathias Krause Committed by Sean Christopherson
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KVM: x86: Ignore CR0.WP toggles in non-paging mode 



If paging is disabled, there are no permission bits to emulate.
Micro-optimize this case to avoid unnecessary work.

Suggested-by: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarMathias Krause <minipli@grsecurity.net>
Link: https://lore.kernel.org/r/20230322013731.102955-4-minipli@grsecurity.net


Co-developed-by: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 01b31714

arch/x86/kvm/x86.c

+13 −7
Original line number Diff line number Diff line
@@ -908,15 +908,21 @@ void kvm_post_set_cr0(struct kvm_vcpu *vcpu, unsigned long old_cr0, unsigned lon 
{

	/*

	 * CR0.WP is incorporated into the MMU role, but only for non-nested,

	 * indirect shadow MMUs.  If TDP is enabled, the MMU's metadata needs

	 * to be updated, e.g. so that emulating guest translations does the

	 * right thing, but there's no need to unload the root as CR0.WP

	 * doesn't affect SPTEs.

	 * indirect shadow MMUs.  If paging is disabled, no updates are needed

	 * as there are no permission bits to emulate.  If TDP is enabled, the

	 * MMU's metadata needs to be updated, e.g. so that emulating guest

	 * translations does the right thing, but there's no need to unload the

	 * root as CR0.WP doesn't affect SPTEs.

	 */

	if (tdp_enabled && (cr0 ^ old_cr0) == X86_CR0_WP) {

	if ((cr0 ^ old_cr0) == X86_CR0_WP) {

		if (!(cr0 & X86_CR0_PG))

			return;



		if (tdp_enabled) {

			kvm_init_mmu(vcpu);

			return;

		}

	}



	if ((cr0 ^ old_cr0) & X86_CR0_PG) {

		kvm_clear_async_pf_completion_queue(vcpu);