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

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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: David Matlack <dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220921173546.2674386-7-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
David Matlack 2022-09-21 10:35:42 -07:00 committed by Paolo Bonzini
parent 897e4526e5
commit f09948ec1f
2 changed files with 31 additions and 31 deletions
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56
arch/x86/kvm/mmu/mmu.c
View File

@ -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,
unsigned int access)
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;
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()))
return RET_PF_EMULATE;
}
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.
*/
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;

6
arch/x86/kvm/mmu/paging_tmpl.h
View File

@ -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;