Re: [PATCH 3/3] xen/vm_event: Add safe to disable vm_event

From: Tamas K Lengyel <tamas@tklengyel.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: "Petre Pircalabu" <ppircalabu@bitdefender.com>,
	"Stefano Stabellini" <sstabellini@kernel.org>,
	"Julien Grall" <julien@xen.org>, "Wei Liu" <wl@xen.org>,
	"Andrew Cooper" <andrew.cooper3@citrix.com>,
	"Ian Jackson" <ian.jackson@eu.citrix.com>,
	"George Dunlap" <george.dunlap@citrix.com>,
	"Alexandru Isaila" <aisaila@bitdefender.com>,
	Xen-devel <xen-devel@lists.xenproject.org>,
	"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [PATCH 3/3] xen/vm_event: Add safe to disable vm_event
Date: Wed, 20 May 2020 09:27:02 -0600	[thread overview]
Message-ID: <CABfawhmsbJJ4-TwCgeVhA7yw+v_YstR3RyyjYJfV17KwYm4=Bg@mail.gmail.com> (raw)
In-Reply-To: <28e50e15-410e-096d-51f1-e304c9ef8cdb@suse.com>

On Wed, May 20, 2020 at 7:45 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 15.05.2020 18:53, Tamas K Lengyel wrote:
> > --- a/xen/arch/x86/hvm/hvm.c
> > +++ b/xen/arch/x86/hvm/hvm.c
> > @@ -563,15 +563,41 @@ void hvm_do_resume(struct vcpu *v)
> >          v->arch.hvm.inject_event.vector = HVM_EVENT_VECTOR_UNSET;
> >      }
> >
> > -    if ( unlikely(v->arch.vm_event) && v->arch.monitor.next_interrupt_enabled )
> > +    if ( unlikely(v->arch.vm_event) )
> >      {
> > -        struct x86_event info;
> > +        struct domain *d = v->domain;
>
> const
>
> > +        if ( v->arch.monitor.next_interrupt_enabled )
> > +        {
> > +            struct x86_event info;
> > +
> > +            if ( hvm_get_pending_event(v, &info) )
> > +            {
> > +                hvm_monitor_interrupt(info.vector, info.type, info.error_code,
> > +                                      info.cr2);
> > +                v->arch.monitor.next_interrupt_enabled = false;
> > +            }
> > +        }
> >
> > -        if ( hvm_get_pending_event(v, &info) )
> > +        if ( d->arch.monitor.safe_to_disable )
> >          {
> > -            hvm_monitor_interrupt(info.vector, info.type, info.error_code,
> > -                                  info.cr2);
> > -            v->arch.monitor.next_interrupt_enabled = false;
> > +            struct vcpu *check_vcpu;
>
> const again, requiring a respective adjustment to patch 2.
>
> > +            bool pending_op = false;
> > +
> > +            for_each_vcpu ( d, check_vcpu )
> > +            {
> > +                if ( vm_event_check_pending_op(check_vcpu) )
> > +                {
> > +                    pending_op = true;
> > +                    break;
> > +                }
> > +            }
> > +
> > +            if ( !pending_op )
> > +            {
> > +                hvm_monitor_safe_to_disable();
>
> This new function returns bool without the caller caring about the
> return value.

Yea, there is actually nothing to be done if the event can't be sent
for whatever reason, I guess I'll just turn it to void.

Tamas