From mboxrd@z Thu Jan 1 00:00:00 1970 From: George Dunlap Subject: Re: Xen 4.3 development update RC2 imminent Date: Wed, 22 May 2013 17:54:53 +0100 Message-ID: <519CF85D.5070702@eu.citrix.com> References: <519B7F67.2050602@citrix.com> <519B8541.8090505@citrix.com> <519BA6F302000078000D7CF2@nat28.tlf.novell.com> <519B9D15.7060004@eu.citrix.com> <519B9DF9.7090303@eu.citrix.com> <519CBEF3.4020701@m2r.biz> <519CDEB7.5090608@eu.citrix.com> <20130522163028.GU11427@reaktio.net> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1"; Format="flowed" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20130522163028.GU11427@reaktio.net> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: =?ISO-8859-1?Q?Pasi_K=E4rkk=E4inen?= Cc: Anthony PERARD , Andrew Cooper , Fabio Fantoni , Jan Beulich , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On 22/05/13 17:30, Pasi K=E4rkk=E4inen wrote: > On Wed, May 22, 2013 at 04:05:27PM +0100, George Dunlap wrote: >>>>>> The emulator in the hypervisor can handle simple SSE instructions >>>>>> like the above quite well. It's not immediately clear to me why >>>>>> hvmemul_do_io() would need to limit the size to no more than a >>>>>> long's width. Perhaps the data passing to the device model may >>>>>> need adjustment to accommodate wider entities... >>>>> Hmm, but the code seems to indicate that the DM can handle wider >>>>> entities, by "reading all ones": >>>>> >>>>> if ( dir =3D=3D IOREQ_READ ) >>>>> memset(p_data, ~0, size); >>>>> >>>>> Anthony, do you want to try making that size check one size bigger >>>>> (e.g., allow it to be 16 or 32)? >>>> No, that obviously won't work, because of the line just following: >>>> >>>> if ( (p_data !=3D NULL) && (dir =3D=3D IOREQ_WRITE) ) >>>> { >>>> memcpy(&value, p_data, size); >>>> p_data =3D NULL; >>>> } >>>> >>>> >>>> value is of size "long", so this won't work. >>>> >>>> -George >>> Thanks for help to solve this problem. >>> Are there news about? >>> >>> Probably this is a stupid question: is this patch related to that >>> problem? >>> http://lists.xen.org/archives/html/xen-devel/2013-05/msg02142.html >> No, I'm afraid that has nothing to do with this issue. I've only >> looked briefly at it, but it appears that the interface between Xen >> and qemu is limited to MMIO accesses of 8 bytes; changing that >> interface is not something we can really do while we're in the >> middle of doing a release. >> >> The only work-around that would be suitable for 4.3 would be if we >> could find an option to tell the X server not to execute SSE >> instructions. If there is no such work-around, then I'm afraid >> we're going to have to disable the interface for 4.3. We'll put it >> on the list of work items for 4.4. >> > Hmm, for testing, can we use cpuid to mask out SSE, > and then try qxl ? That had occurred to me -- Andrew / Jan, do you know which flag might = disable this particular instruction? I guess we could try just disabling all the SSE instructions. Fabio: Can you do the following: * On your host, do "cat /proc/cpuinfo". Under "flags" there will be a = big list. Look for all of the ones that have "sse" in them. On my AMD box, that includes sse, sse2, ssse3, sse4_1, and sse4_2. * In your xl.cfg, add a cpuid with each of those flags disabled. On my box, it looks like this: cpuid=3D"host,sse=3D0,sse2=3D0,ssse3=3D0,sse4_1=3D0,sse4_2=3D0" Then run your system with Anthony's patch and see if you still get the = crash. -George