2019-06-20 11:03:19

by Vitaly Kuznetsov

Subject: [PATCH RFC 2/5] x86: KVM: svm: avoid flooding logs when skip_emulated_instruction() fails

When we're unable to skip instruction with kvm_emulate_instruction() we
will not advance RIP and most likely the guest will get stuck as
consequitive attempts to execute the same instruction will likely result
in the same behavior.

As we're not supposed to see these messages under normal conditions, switch
to pr_err_once().

Signed-off-by: Vitaly Kuznetsov <[email protected]>
---
arch/x86/kvm/svm.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 982c6b9bfc90..68f1f0218c95 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -781,7 +781,8 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu)
if (!svm->next_rip) {
if (kvm_emulate_instruction(vcpu, EMULTYPE_SKIP) !=
EMULATE_DONE)
- printk(KERN_DEBUG "%s: NOP\n", __func__);
+ pr_err_once("KVM: %s: unable to skip instruction\n",
+ __func__);
return;
}
if (svm->next_rip - kvm_rip_read(vcpu) > MAX_INST_SIZE)
--
2.20.1

2019-06-20 18:46:49

by Jim Mattson

Subject: Re: [PATCH RFC 2/5] x86: KVM: svm: avoid flooding logs when skip_emulated_instruction() fails

On Thu, Jun 20, 2019 at 4:02 AM Vitaly Kuznetsov <[email protected]> wrote:
>
> When we're unable to skip instruction with kvm_emulate_instruction() we
> will not advance RIP and most likely the guest will get stuck as
> consequitive attempts to execute the same instruction will likely result
> in the same behavior.
>
> As we're not supposed to see these messages under normal conditions, switch
> to pr_err_once().
>
> Signed-off-by: Vitaly Kuznetsov <[email protected]>
Reviewed-by: Jim Mattson <[email protected]>