Re: [PATCH v3 0/3] KVM: Set vcpu->preempted/ready iff scheduled out while running

[David Matlack <dmatlack@google.com>]

On Tue, Jun 18, 2024 at 2:41 PM Sean Christopherson <seanjc@google.com> wrote:
>
> On Fri, 03 May 2024 11:17:31 -0700, David Matlack wrote:
> > This series changes KVM to mark a vCPU as preempted/ready if-and-only-if
> > it's scheduled out while running. i.e. Do not mark a vCPU
> > preempted/ready if it's scheduled out during a non-KVM_RUN ioctl() or
> > when userspace is doing KVM_RUN with immediate_exit=true.
> >
> > This is a logical extension of commit 54aa83c90198 ("KVM: x86: do not
> > set st->preempted when going back to user space"), which  stopped
> > marking a vCPU as preempted when returning to userspace. But if userspace
> > invokes a KVM vCPU ioctl() that gets preempted, the vCPU will be marked
> > preempted/ready. This is arguably incorrect behavior since the vCPU was
> > not actually preempted while the guest was running, it was preempted
> > while doing something on behalf of userspace.
> >
> > [...]
>
> Applied to kvm-x86 generic, with minor changelog tweaks (me thinks you've been
> away from upstream too long ;-) ).  Thanks!

Thanks for the cleanups. Looks like you replaced "[Tt]his commit"
throughout. Anything else (so I can avoid the same mistakes in the
future)?

>
> [1/3] KVM: Introduce vcpu->wants_to_run
>       https://github.com/kvm-x86/linux/commit/a6816314af57
> [2/3] KVM: Ensure new code that references immediate_exit gets extra scrutiny
>       https://github.com/kvm-x86/linux/commit/4b23e0c199b2
> [3/3] KVM: Mark a vCPU as preempted/ready iff it's scheduled out while running
>       https://github.com/kvm-x86/linux/commit/118964562969
>
> --
> https://github.com/kvm-x86/linux/tree/next