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KVM: x86: Return to userspace with internal error on unexpected exit reason

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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@oracle.com>
Reviewed-by: Nikita Leshenko <nikita.leshchenko@oracle.com>
Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Liran Alon 2019-08-26 13:16:43 +03:00 committed by Paolo Bonzini
parent 1edce0a9eb
commit 7396d337cf
3 changed files with 17 additions and 5 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

11
arch/x86/kvm/svm.c
View file

@ -4981,9 +4981,14 @@ 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);

9
arch/x86/kvm/vmx/vmx.c
View file

@ -5870,8 +5870,13 @@ 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;
}
}

2
include/uapi/linux/kvm.h
View file

@ -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 {