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x86: kvm: svm: propagate errors from skip_emulated_instruction()

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On AMD, kvm_x86_ops->skip_emulated_instruction(vcpu) can, in theory,
fail: in !nrips case we call kvm_emulate_instruction(EMULTYPE_SKIP).
Currently, we only do printk(KERN_DEBUG) when this happens and this
is not ideal. Propagate the error up the stack.

On VMX, skip_emulated_instruction() doesn't fail, we have two call
sites calling it explicitly: handle_exception_nmi() and
handle_task_switch(), we can just ignore the result.

On SVM, we also have two explicit call sites:
svm_queue_exception() and it seems we don't need to do anything there as
we check if RIP was advanced or not. In task_switch_interception(),
however, we are better off not proceeding to kvm_task_switch() in case
skip_emulated_instruction() failed.

Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Vitaly Kuznetsov
2019-08-13 15:53:30 +02:00
committed by Paolo Bonzini
parent 05402f6454
commit f8ea7c6049
4 changed files with 38 additions and 22 deletions
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6
arch/x86/kvm/x86.c
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@@ -6390,9 +6390,11 @@ static void kvm_vcpu_do_singlestep(struct kvm_vcpu *vcpu, int *r)
int kvm_skip_emulated_instruction(struct kvm_vcpu *vcpu)
{
unsigned long rflags = kvm_x86_ops->get_rflags(vcpu);
int r = EMULATE_DONE;
int r;
kvm_x86_ops->skip_emulated_instruction(vcpu);
r = kvm_x86_ops->skip_emulated_instruction(vcpu);
if (unlikely(r != EMULATE_DONE))
return 0;
/*
* rflags is the old, "raw" value of the flags. The new value has