From mboxrd@z Thu Jan 1 00:00:00 1970 From: Fabio Fantoni Subject: Re: Xen 4.3 development update RC2 imminent Date: Thu, 23 May 2013 12:31:57 +0200 Message-ID: <519DF01D.6020800@m2r.biz> 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> <519CF85D.5070702@eu.citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1"; Format="flowed" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <519CF85D.5070702@eu.citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: George Dunlap Cc: Anthony PERARD , Andrew Cooper , Jan Beulich , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org Il 22/05/2013 18:54, George Dunlap ha scritto: > 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 Thanks, I tried it. On windows domU I get a blu screen with "stop 5d" = (even without qxl set) and on linux domU the domU crashes without = showing errors on qemu log.