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KVM: x86/mmu: Move private vs. shared check above slot validity checks

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Prioritize private vs. shared gfn attribute checks above slot validity
checks to ensure a consistent userspace ABI.  E.g. as is, KVM will exit to
userspace if there is no memslot, but emulate accesses to the APIC access
page even if the attributes mismatch.

Fixes: 8dd2eee9d5 ("KVM: x86/mmu: Handle page fault for private memory")
Cc: Yu Zhang <yu.c.zhang@linux.intel.com>
Cc: Chao Peng <chao.p.peng@linux.intel.com>
Cc: Fuad Tabba <tabba@google.com>
Cc: Michael Roth <michael.roth@amd.com>
Cc: Isaku Yamahata <isaku.yamahata@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Message-ID: <20240228024147.41573-10-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2024-02-27 18:41:40 -08:00 committed by Paolo Bonzini
parent 07702e5a6d
commit 44f42ef37d
1 changed files with 15 additions and 5 deletions
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20
arch/x86/kvm/mmu/mmu.c
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@ -4316,11 +4316,6 @@ static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
return RET_PF_EMULATE; return RET_PF_EMULATE;
} }
if (fault->is_private != kvm_mem_is_private(vcpu->kvm, fault->gfn)) {
kvm_mmu_prepare_memory_fault_exit(vcpu, fault);
return -EFAULT;
}
if (fault->is_private) if (fault->is_private)
return kvm_faultin_pfn_private(vcpu, fault); return kvm_faultin_pfn_private(vcpu, fault);
@ -4358,9 +4353,24 @@ static int kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
{ {
int ret; int ret;
/*
* Note that the mmu_invalidate_seq also serves to detect a concurrent
* change in attributes. is_page_fault_stale() will detect an
* invalidation relate to fault->fn and resume the guest without
* installing a mapping in the page tables.
*/
fault->mmu_seq = vcpu->kvm->mmu_invalidate_seq; fault->mmu_seq = vcpu->kvm->mmu_invalidate_seq;
smp_rmb(); smp_rmb();
/*
* Now that we have a snapshot of mmu_invalidate_seq we can check for a
* private vs. shared mismatch.
*/
if (fault->is_private != kvm_mem_is_private(vcpu->kvm, fault->gfn)) {
kvm_mmu_prepare_memory_fault_exit(vcpu, fault);
return -EFAULT;
}
/* /*
* Check for a relevant mmu_notifier invalidation event before getting * Check for a relevant mmu_notifier invalidation event before getting
* the pfn from the primary MMU, and before acquiring mmu_lock. * the pfn from the primary MMU, and before acquiring mmu_lock.