Re: [PATCH 1/3] KVM: SVM: Get rid of handle_fastpath_set_msr_irqoff()

[Wanpeng Li]

On Wed, 9 Sep 2020 at 16:23, Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> wrote:
>
> Wanpeng Li <kernellwp@xxxxxxxxx> writes:
>
> > From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
> >
> > Analysis from Sean:
> >
> >  | svm->next_rip is reset in svm_vcpu_run() only after calling
> >  | svm_exit_handlers_fastpath(), which will cause SVM's
> >  | skip_emulated_instruction() to write a stale RIP.
> >
>
> This should only happen when svm->vmcb->control.next_rip is not set by
> hardware as skip_emulated_instruction() itself sets 'svm->next_rip'
> otherwise, right?

The bug is reported here
https://bugzilla.kernel.org/show_bug.cgi?id=209155 , the old machine
which the reporter uses doesn't have NRIP save on #VMEXIT support. :)

    Wanpeng