Revert "KVM: SVM: avoid infinite loop on NPF from bad address"

commit 31c25585695abdf03d6160aa6d829e855b256329 upstream.

Revert a completely broken check on an "invalid" RIP in SVM's workaround
for the DecodeAssists SMAP errata.  kvm_vcpu_gfn_to_memslot() obviously
expects a gfn, i.e. operates in the guest physical address space, whereas
RIP is a virtual (not even linear) address.  The "fix" worked for the
problematic KVM selftest because the test identity mapped RIP.

Fully revert the hack instead of trying to translate RIP to a GPA, as the
non-SEV case is now handled earlier, and KVM cannot access guest page
tables to translate RIP.

This reverts commit e72436bc3a5206f95bb384e741154166ddb3202e.

Fixes: e72436bc3a52 ("KVM: SVM: avoid infinite loop on NPF from bad address")
Reported-by: Liam Merwick <liam.merwick@oracle.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
Message-Id: <20220120010719.711476-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index e64f162..f7e9cde 100644 (file)
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4456,13 +4456,6 @@ static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, void *insn, int i
        if (likely(!insn || insn_len))
                return true;
 
-       /*
-        * If RIP is invalid, go ahead with emulation which will cause an
-        * internal error exit.
-        */
-       if (!kvm_vcpu_gfn_to_memslot(vcpu, kvm_rip_read(vcpu) >> PAGE_SHIFT))
-               return true;
-
        cr4 = kvm_read_cr4(vcpu);
        smep = cr4 & X86_CR4_SMEP;
        smap = cr4 & X86_CR4_SMAP;

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index c6bfd4e..13aff13 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2104,7 +2104,6 @@ struct kvm_memory_slot *kvm_vcpu_gfn_to_memslot(struct kvm_vcpu *vcpu, gfn_t gfn
 
        return NULL;
 }
-EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_memslot);
 
 bool kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn)
 {