linux-kernel - Re: [kvm-devel] [RFC] Deferred interrupt handling.

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]

Date:	Wed, 18 Jul 2007 19:46:13 +0300
From:	Avi Kivity <avi@...ranet.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	Dor Laor <dor.laor@...ranet.com>, kvm-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: Re: [kvm-devel] [RFC] Deferred interrupt handling.

Alan Cox wrote:
>> What if we will force the specific device to the end of the list. Once
>> IRQ_NONE was returned by the other devices, we will mask the irq,
>> forward the irq to the guest, issue a timer for 1msec. Motivation:
>> 1msec is long enough for the guest to ack the irq + host unmask the irq
>>     
>
> It makes no difference. The deadlock isn't fixable by timing hacks.
> Consider the following sequence
>
>
> 	Guest0	-	blocked on I/O
>
> 	IRQ14 from your hardware
> 		Block IRQ14
> 		Sent to guest (guest is blocked)
>
> 	IRQ14 from hard disk
> 		Ignored (as blocked)
>
> 	Deadlock
>   

IMO the only reasonable solution is to disallow interrupt forwarding
with shared irqs.  If someone later comes up with a bright idea, we can
implement it.  Otherwise the problem will solve itself with hardware
moving to msi.


-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

-
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/