Re: [PATCH] KVM: SVM: fix task switch emulation on INTn instruction.

Maxim Levitsky
2022-07-14T14:00:16Z

On Thu, 2022-07-14 at 15:50 +0200, Maciej S. Szmigiero wrote:
> On 14.07.2022 14:44, Maxim Levitsky wrote:
> > Recently KVM's SVM code switched to re-injecting software interrupt events,
> > if something prevented their delivery.
> >
> > Task switch due to task gate in the IDT, however is an exception
> > to this rule, because in this case, INTn instruction causes
> > a task switch intercept and its emulation completes the INTn
> > emulation as well.
> >
> > Add a missing case to task_switch_interception for that.
> >
> > This fixes 32 bit kvm unit test taskswitch2.
> >
> > Fixes: 7e5b5ef8dca322 ("KVM: SVM: Re-inject INTn instead of retrying the insn on "failure"")
> >
> > Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> > ---
>
> That's a good catch, your patch looks totally sensible to me.
> People running Win 3.x or OS/2 on top of KVM will surely be grateful for it :)

Yes and also people who run 32 bit kvm unit tests :)

BTW, I do have a win98 VM which I run once in a while under KVM.
On Intel it works very well, on AMD, only works without NPT and without MMU
pre-fetching, due to fact that the OS doesn't correctly invalidate TLB entries.

I do need to test KVM with OS/2 on one of the weekends.... ;-)

Thanks for the review,
Best regards,
Maxim Levitsky

>
> Reviewed-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
>
> Thanks,
> Maciej
>