linux-kernel - Re: [PATCHv4 3/5] kvm: host side for eoi optimization

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20120516170427.GA22784@amt.cnet>
Date:	Wed, 16 May 2012 14:04:27 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Gleb Natapov <gleb@...hat.com>, x86@...nel.org,
	kvm@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Avi Kivity <avi@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv4 3/5] kvm: host side for eoi optimization

On Wed, May 16, 2012 at 07:50:48PM +0300, Michael S. Tsirkin wrote:
> On Wed, May 16, 2012 at 07:32:06PM +0300, Gleb Natapov wrote:
> > On Wed, May 16, 2012 at 07:22:47PM +0300, Michael S. Tsirkin wrote:
> > > On Wed, May 16, 2012 at 12:49:40PM -0300, Marcelo Tosatti wrote:
> > > > > @@ -1245,9 +1306,20 @@ int kvm_get_apic_interrupt(struct kvm_vcpu *vcpu)
> > > > >  	int vector = kvm_apic_has_interrupt(vcpu);
> > > > >  	struct kvm_lapic *apic = vcpu->arch.apic;
> > > > >  
> > > > > -	if (vector == -1)
> > > > > +	/* Detect interrupt nesting and disable EOI optimization */
> > > > > +	if (pv_eoi_enabled(vcpu) && vector == -2)
> > > > > +		pv_eoi_clr_pending(vcpu);
> > > > > +
> > > > > +	if (vector < 0)
> > > > 
> > > > With interrupt window exiting, the guest will exit:
> > > > 
> > > > - as soon as it sets RFLAGS.IF=1 and there is any 
> > > > interrupt pending in IRR.
> > > > - any new interrupt is set in IRR will kick vcpu
> > > > out of guest mode and recalculate interrupt-window-exiting.
> > > > 
> > > > Doesnt this make this bit unnecessary ?
> > > 
> > > Looks like we could cut it out.  But I'm not sure how architectural it is
> > > that we exit on interrupt window.
> > We request exit on interrupt window only if there is pending irq that
> > can be delivered on a guest entry.
> 
> Aha. If so what Marcelo proposed won't work I think: if we inject A then B
> which is lower priority, we need an exit on EOI, we can't inject
> immediately.

Please describe the scenario clearly, i can't see the problem.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/