linux-kernel - Re: [PATCH RFC] kvm: enable irq injection from interrupt context

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20100916102047.GY3008@redhat.com>
Date:	Thu, 16 Sep 2010 12:20:47 +0200
From:	Gleb Natapov <gleb@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] kvm: enable irq injection from interrupt context

On Thu, Sep 16, 2010 at 12:13:39PM +0200, Michael S. Tsirkin wrote:
> On Thu, Sep 16, 2010 at 12:13:32PM +0200, Gleb Natapov wrote:
> > On Thu, Sep 16, 2010 at 11:53:10AM +0200, Michael S. Tsirkin wrote:
> > > On Thu, Sep 16, 2010 at 11:46:03AM +0200, Avi Kivity wrote:
> > > >  On 09/16/2010 11:25 AM, Gleb Natapov wrote:
> > > > >>
> > > > >>  MSI only appeared in rhel6, older guests still use level interrupts.
> > > > >So they are already slow for other reasons.
> > > > >
> > > > 
> > > > Exactly, for example they need to exit to userspace to ack the
> > > > interrupt.  That's far slower than the workqueue.
> > > 
> > > Well, this is not exactly comparable: you might get
> > > same irq asserted multiple times and only deasserted once.
> > > 
> > Are we talking about level interrupts? Why would you assert level
> > triggered interrupt multiple times before deasserting it?
> 
> User of irqfd has no way to know what current interrupt level is.
> So it has to keep asserting.
> 
Why can't it keep track of current level?

--
			Gleb.
--
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/