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authorBrijesh Singh <brijesh.singh@amd.com>2017-12-04 10:57:40 -0600
committerBrijesh Singh <brijesh.singh@amd.com>2017-12-04 13:33:14 -0600
commit00b10fe1046c4b2232097a7ffaa9238c7e479388 (patch)
tree97baced4011d1ffdc3c76d3b36f3090741959c59
parent35c6f649bbb2e3f367116307273f998f0bf3e08e (diff)
KVM: X86: Restart the guest when insn_len is zero and SEV is enabled
On AMD platforms, under certain conditions insn_len may be zero on #NPF. This can happen if a guest gets a page-fault on data access but the HW table walker is not able to read the instruction page (e.g instruction page is not present in memory). Typically, when insn_len is zero, x86_emulate_instruction() walks the guest page table and fetches the instruction bytes from guest memory. When SEV is enabled, the guest memory is encrypted with guest-specific key hence hypervisor will not able to fetch the instruction bytes. In those cases we simply restart the guest. I have encountered this issue when running kernbench inside the guest. Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: "Radim Krčmář" <rkrcmar@redhat.com> Cc: Joerg Roedel <joro@8bytes.org> Cc: Borislav Petkov <bp@suse.de> Cc: Tom Lendacky <thomas.lendacky@amd.com> Cc: x86@kernel.org Cc: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
-rw-r--r--arch/x86/kvm/mmu.c10
-rw-r--r--arch/x86/kvm/svm.c6
2 files changed, 14 insertions, 2 deletions
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index e5e66e5c6640..d5e5dbd0e5ad 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4950,6 +4950,16 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u64 error_code,
if (mmio_info_in_cache(vcpu, cr2, direct))
emulation_type = 0;
emulate:
+ /*
+ * On AMD platforms, under certain conditions insn_len may be zero on #NPF.
+ * This can happen if a guest gets a page-fault on data access but the HW
+ * table walker is not able to read the instruction page (e.g instruction
+ * page is not present in memory). In those cases we simply restart the
+ * guest.
+ */
+ if (unlikely(insn && !insn_len))
+ return 1;
+
er = x86_emulate_instruction(vcpu, cr2, emulation_type, insn, insn_len);
switch (er) {
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 3e848f952b4f..ec5df5752995 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -2436,7 +2436,8 @@ static int pf_interception(struct vcpu_svm *svm)
u64 error_code = svm->vmcb->control.exit_info_1;
return kvm_handle_page_fault(&svm->vcpu, error_code, fault_address,
- svm->vmcb->control.insn_bytes,
+ static_cpu_has(X86_FEATURE_DECODEASSISTS) ?
+ svm->vmcb->control.insn_bytes : NULL,
svm->vmcb->control.insn_len);
}
@@ -2447,7 +2448,8 @@ static int npf_interception(struct vcpu_svm *svm)
trace_kvm_page_fault(fault_address, error_code);
return kvm_mmu_page_fault(&svm->vcpu, fault_address, error_code,
- svm->vmcb->control.insn_bytes,
+ static_cpu_has(X86_FEATURE_DECODEASSISTS) ?
+ svm->vmcb->control.insn_bytes : NULL,
svm->vmcb->control.insn_len);
}