Re: [PATCH 3/3] x86/monitor: Add new monitor event to catch all vmexits

[Tamas K Lengyel <tamas@xxxxxxxxxxxxx>]

On Thu, Apr 28, 2022 at 9:56 AM Roger Pau Monné <roger.pau@xxxxxxxxxx> wrote:
>
> On Wed, Apr 27, 2022 at 11:34:20AM -0400, Tamas K Lengyel wrote:
> > Add monitor event that hooks the vmexit handler allowing for both sync and
> > async monitoring of events. With async monitoring an event is placed on the
> > monitor ring for each exit and the rest of the vmexit handler resumes 
> > normally.
> > If there are additional monitor events configured those will also place 
> > their
> > respective events on the monitor ring.
> >
> > With the sync version an event is placed on the monitor ring but the handler
> > does not get resumed, thus the sync version is only useful when the VM is 
> > not
> > expected to resume normally after the vmexit. Our use-case is primarily with
> > the sync version with VM forks where the fork gets reset after sync vmexit
> > event, thus the rest of the vmexit handler can be safely skipped. This is
> > very useful when we want to avoid Xen crashing the VM under any 
> > circumstance,
> > for example during fuzzing. Collecting all vmexit information regardless of
> > the root cause makes it easier to reason about the state of the VM on the
> > monitor side, hence we opt to receive all events, even for external 
> > interrupt
> > and NMI exits and let the monitor agent decide how to proceed.
> >
> > Signed-off-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxx>
>
> Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
>
> Thanks, Roger.

Thank you!
Tamas