From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: Re: Re: 2.6.28.7 domU: 32-bit emulation seems to be broken Date: Fri, 14 Aug 2009 13:55:27 -0700 Message-ID: <4A85CF3F.9020701@goop.org> References: <49BFD56B.1040003@goop.org> <20090810132121.3859d865.listen@mjh.name> <200908101459.31377.Christoph.Egger@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <200908101459.31377.Christoph.Egger@amd.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Christoph Egger Cc: xen-devel@lists.xensource.com, =?ISO-8859-15?Q?Milan_Holz=E4pfel?= List-Id: xen-devel@lists.xenproject.org On 08/10/09 05:59, Christoph Egger wrote: >> I still notice this problem with vanilla 2.6.30.4 domU under Xen 3.3.2 >> (32 bit binaries on a 64 bit domU kernel segfault, AMD CPU). vdso32=0 >> still helps. >> >> Any news? >> > > What does Linux use w/o vdso32=0 on your box ? Does it use sysenter, syscall > or int 0x80 ? > > Do you boot the DomU directly or does this happen after migration from > an Intel box ? > There appears to be a bug in the 64-bit xen_sysret32, which attempts to take the sysret environment and turn it into an iret hypercall (since iret is the only way to do a 64-bit kernel -> 32-bit user return). I don't have an AMD test machine on hand, so I haven't had a chance to work out what's actually failing. I couldn't see anything wrong by staring at the code, but that probably means I was either starting hard at the bug, or looking right next to the bug... Could you try looking at this? J