Commit 354c908c authored by David Matlack's avatar David Matlack Committed by Paolo Bonzini
Browse files

KVM: x86/mmu: Handle no-slot faults in kvm_faultin_pfn() 



Handle faults on GFNs that do not have a backing memslot in
kvm_faultin_pfn() and drop handle_abnormal_pfn(). This eliminates
duplicate code in the various page fault handlers.

Opportunistically tweak the comment about handling gfn > host.MAXPHYADDR
to reflect that the effect of returning RET_PF_EMULATE at that point is
to avoid creating an MMIO SPTE for such GFNs.

No functional change intended.

Signed-off-by: default avatarDavid Matlack <dmatlack@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220921173546.2674386-7-dmatlack@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent cd08d178

arch/x86/kvm/mmu/mmu.c

+30 −26
Original line number Diff line number Diff line
@@ -3218,28 +3218,32 @@ static int kvm_handle_error_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fa 
	return -EFAULT;

}



static int handle_abnormal_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,

static int kvm_handle_noslot_fault(struct kvm_vcpu *vcpu,

				   struct kvm_page_fault *fault,

				   unsigned int access)

{

	if (unlikely(!fault->slot)) {

	gva_t gva = fault->is_tdp ? 0 : fault->addr;



	vcpu_cache_mmio_info(vcpu, gva, fault->gfn,

			     access & shadow_mmio_access_mask);



	/*

	 * If MMIO caching is disabled, emulate immediately without

	 * touching the shadow page tables as attempting to install an

		 * MMIO SPTE will just be an expensive nop.  Do not cache MMIO

		 * whose gfn is greater than host.MAXPHYADDR, any guest that

		 * generates such gfns is running nested and is being tricked

		 * by L0 userspace (you can observe gfn > L1.MAXPHYADDR if

		 * and only if L1's MAXPHYADDR is inaccurate with respect to

		 * the hardware's).

		 */

		if (unlikely(!enable_mmio_caching) ||

		    unlikely(fault->gfn > kvm_mmu_max_gfn()))

	 * MMIO SPTE will just be an expensive nop.

	 */

	if (unlikely(!enable_mmio_caching))

		return RET_PF_EMULATE;



	/*

	 * Do not create an MMIO SPTE for a gfn greater than host.MAXPHYADDR,

	 * any guest that generates such gfns is running nested and is being

	 * tricked by L0 userspace (you can observe gfn > L1.MAXPHYADDR if and

	 * only if L1's MAXPHYADDR is inaccurate with respect to the

	 * hardware's).

	 */

	if (unlikely(fault->gfn > kvm_mmu_max_gfn()))

		return RET_PF_EMULATE;

	}



	return RET_PF_CONTINUE;

}
@@ -4248,7 +4252,8 @@ static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault 
	return RET_PF_CONTINUE;

}



static int kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)

static int kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,

			   unsigned int access)

{

	int ret;
@@ -4262,6 +4267,9 @@ static int kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) 
	if (unlikely(is_error_pfn(fault->pfn)))

		return kvm_handle_error_pfn(vcpu, fault);



	if (unlikely(!fault->slot))

		return kvm_handle_noslot_fault(vcpu, fault, access);



	return RET_PF_CONTINUE;

}
@@ -4312,11 +4320,7 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault 
	if (r)

		return r;



	r = kvm_faultin_pfn(vcpu, fault);

	if (r != RET_PF_CONTINUE)

		return r;



	r = handle_abnormal_pfn(vcpu, fault, ACC_ALL);

	r = kvm_faultin_pfn(vcpu, fault, ACC_ALL);

	if (r != RET_PF_CONTINUE)

		return r;

arch/x86/kvm/mmu/paging_tmpl.h

+1 −5
Original line number Diff line number Diff line
@@ -837,11 +837,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault 
	else

		fault->max_level = walker.level;



	r = kvm_faultin_pfn(vcpu, fault);

	if (r != RET_PF_CONTINUE)

		return r;



	r = handle_abnormal_pfn(vcpu, fault, walker.pte_access);

	r = kvm_faultin_pfn(vcpu, fault, walker.pte_access);

	if (r != RET_PF_CONTINUE)

		return r;