KVM: x86/mmu: check for invalid async page faults involving private memory

Right now the error code is not used when an async page fault is completed.
This is not a problem in the current code, but it is untidy.  For protected
VMs, we will also need to check that the page attributes match the current
state of the page, because asynchronous page faults can only occur on
shared pages (private pages go through kvm_faultin_pfn_private() instead of
__gfn_to_pfn_memslot()).

Start by piping the error code from kvm_arch_setup_async_pf() to
kvm_arch_async_page_ready() via the architecture-specific async page
fault data.  For now, it can be used to assert that there are no
async page faults on private memory.

Extracted from a patch by Isaku Yamahata.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 816d248264dbae1cc91cf302ddb81a8cfe9b7977..0369e9efe4296552011a25cbffa083e27ebb0048 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1849,6 +1849,7 @@ struct kvm_arch_async_pf {
        gfn_t gfn;
        unsigned long cr3;
        bool direct_map;
+       u64 error_code;
 };
 
 extern u32 __read_mostly kvm_nr_uret_msrs;

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 34aef57f200a190d79ceccb6af01c3eb0de8d3c8..4bb121b5f58e45aa0607cfc13c48b70110b6cdc2 100644 (file)
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4206,24 +4206,28 @@ static u32 alloc_apf_token(struct kvm_vcpu *vcpu)
        return (vcpu->arch.apf.id++ << 12) | vcpu->vcpu_id;
 }
 
-static bool kvm_arch_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
-                                   gfn_t gfn)
+static bool kvm_arch_setup_async_pf(struct kvm_vcpu *vcpu,
+                                   struct kvm_page_fault *fault)
 {
        struct kvm_arch_async_pf arch;
 
        arch.token = alloc_apf_token(vcpu);
-       arch.gfn = gfn;
+       arch.gfn = fault->gfn;
+       arch.error_code = fault->error_code;
        arch.direct_map = vcpu->arch.mmu->root_role.direct;
        arch.cr3 = kvm_mmu_get_guest_pgd(vcpu, vcpu->arch.mmu);
 
-       return kvm_setup_async_pf(vcpu, cr2_or_gpa,
-                                 kvm_vcpu_gfn_to_hva(vcpu, gfn), &arch);
+       return kvm_setup_async_pf(vcpu, fault->addr,
+                                 kvm_vcpu_gfn_to_hva(vcpu, fault->gfn), &arch);
 }
 
 void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
 {
        int r;
 
+       if (WARN_ON_ONCE(work->arch.error_code & PFERR_PRIVATE_ACCESS))
+               return;
+
        if ((vcpu->arch.mmu->root_role.direct != work->arch.direct_map) ||
              work->wakeup_all)
                return;
@@ -4236,7 +4240,7 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
              work->arch.cr3 != kvm_mmu_get_guest_pgd(vcpu, vcpu->arch.mmu))
                return;
 
-       kvm_mmu_do_page_fault(vcpu, work->cr2_or_gpa, 0, true, NULL);
+       kvm_mmu_do_page_fault(vcpu, work->cr2_or_gpa, work->arch.error_code, true, NULL);
 }
 
 static inline u8 kvm_max_level_for_order(int order)
@@ -4333,7 +4337,7 @@ static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
                        trace_kvm_async_pf_repeated_fault(fault->addr, fault->gfn);
                        kvm_make_request(KVM_REQ_APF_HALT, vcpu);
                        return RET_PF_RETRY;
-               } else if (kvm_arch_setup_async_pf(vcpu, fault->addr, fault->gfn)) {
+               } else if (kvm_arch_setup_async_pf(vcpu, fault)) {
                        return RET_PF_RETRY;
                }
        }