From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: Re: Bug#544145: Crash with paravirt-ops 2.6.31.6 kernel Date: Mon, 23 Nov 2009 16:52:26 -0800 Message-ID: <4B0B2E4A.7020805@goop.org> References: <28846609.721258484676784.JavaMail.root@ifrit.dereferenced.org> <20091122095403.GA1496@wavehammer.waldi.eu.org> <1258989935.7590.52.camel@zakaz.uk.xensource.com> <20091123163104.GA23475@wavehammer.waldi.eu.org> <1258994579.7590.78.camel@zakaz.uk.xensource.com> <20091123172334.GA25056@wavehammer.waldi.eu.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20091123172334.GA25056@wavehammer.waldi.eu.org> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Bastian Blank Cc: "xen-devel@lists.xensource.com" , Ian Campbell , "544145@bugs.debian.org" <544145@bugs.debian.org> List-Id: xen-devel@lists.xenproject.org On 11/23/09 09:23, Bastian Blank wrote: >> I don't believe that is the case (the processor would have to carry some >> state for the entire duration of a syscall for it to make any >> difference). I think the spec simply assumes that an OS author would >> want to use sysret if they used syscall. >> > Well, it is documented this way. If you ignore it, it can work (and does > in this case) but is undefined behaviour. > Linux freely uses iret to return from syscall for things like fork and exec. They are complimentary instructions, but nothing requires them to be paired. J