Receiving an unexpected exit reason from hardware should be considered
as a severe bug in KVM. Therefore, instead of just injecting #UD to
guest and ignore it, exit to userspace on internal error so that
it could handle it properly (probably by terminating guest).
In addition, prefer to use vcpu_unimpl() instead of WARN_ONCE()
as handling unexpected exit reason should be a rare unexpected
event (that was expected to never happen) and we prefer to print
a message on it every time it occurs to guest.
Furthermore, dump VMCS/VMCB to dmesg to assist diagnosing such cases.
Reviewed-by: Mihai Carabas <mihai.carabas@xxxxxxxxxx>
Reviewed-by: Nikita Leshenko <nikita.leshchenko@xxxxxxxxxx>
Reviewed-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
Signed-off-by: Liran Alon <liran.alon@xxxxxxxxxx>
---
arch/x86/kvm/svm.c | 11 ++++++++---
arch/x86/kvm/vmx/vmx.c | 9 +++++++--
include/uapi/linux/kvm.h | 2 ++
3 files changed, 17 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index d685491fce4d..6462c386015d 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -5026,9 +5026,14 @@ static int handle_exit(struct kvm_vcpu *vcpu)
if (exit_code >= ARRAY_SIZE(svm_exit_handlers)
|| !svm_exit_handlers[exit_code]) {
- WARN_ONCE(1, "svm: unexpected exit reason 0x%x\n", exit_code);
- kvm_queue_exception(vcpu, UD_VECTOR);
- return 1;
+ vcpu_unimpl(vcpu, "svm: unexpected exit reason 0x%x\n", exit_code);
+ dump_vmcb(vcpu);
+ vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+ vcpu->run->internal.suberror =
+ KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON;
+ vcpu->run->internal.ndata = 1;
+ vcpu->run->internal.data[0] = exit_code;
+ return 0;
}
return svm_exit_handlers[exit_code](svm);
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 42ed3faa6af8..b5b5b2e5dac5 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5887,8 +5887,13 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu)
else {
vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n",
exit_reason);
- kvm_queue_exception(vcpu, UD_VECTOR);
- return 1;
+ dump_vmcs();
+ vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+ vcpu->run->internal.suberror =
+ KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON;
+ vcpu->run->internal.ndata = 1;
+ vcpu->run->internal.data[0] = exit_reason;
+ return 0;
}
}
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 5e3f12d5359e..42070aa5f4e6 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -243,6 +243,8 @@ struct kvm_hyperv_exit {
#define KVM_INTERNAL_ERROR_SIMUL_EX 2
/* Encounter unexpected vm-exit due to delivery event. */
#define KVM_INTERNAL_ERROR_DELIVERY_EV 3
+/* Encounter unexpected vm-exit reason */
+#define KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON 4
/* for KVM_RUN, returned by mmap(vcpu_fd, offset=0) */
struct kvm_run {
--
2.20.1
