From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH] libxl: Remove qxl support for the 4.3 release Date: Wed, 29 May 2013 23:25:36 +0100 Message-ID: <51A68060.7010500@citrix.com> References: <1369813427.22605.38.camel@dagon.hellion.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1369813427.22605.38.camel@dagon.hellion.org.uk> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell Cc: George Dunlap , Keir Fraser , Ian Jackson , Fabio Fantoni , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On 29/05/2013 08:43, Ian Campbell wrote: > On Tue, 2013-05-28 at 19:09 +0100, Keir Fraser wrote: >> On 28/05/2013 17:51, "Ian Jackson" wrote: >> >>> George Dunlap writes ("[PATCH] libxl: Remove qxl support for the 4.3 >>> release"): >>>> The qxl drivers for Windows and Linux end up calling instructions >>>> that cannot be used for MMIO at the moment. Just for the 4.3 release, >>>> remove qxl support. >>>> >>>> This patch should be reverted as soon as the 4.4 development window opens. >>>> >>>> The issue in question: >>>> >>>> (XEN) emulate.c:88:d18 bad mmio size 16 >>>> (XEN) io.c:201:d18 MMIO emulation failed @ 0033:7fd2de390430: f3 0f 6f >>>> 19 41 83 e8 403 >>>> >>>> The instruction in question is "movdqu (%rcx),%xmm3". Xen knows how >>>> to emulate it, but unfortunately %xmm3 is 16 bytes long, and the interface >>>> between Xen and qemu at the moment would appear to only allow MMIO accesses >>>> of 8 bytes. >>>> >>>> It's too late in the release cycle to find a fix or a workaround. >>> Acked-by: Ian Jackson >> It could be plumbed through hvmemul_do_io's multi-cycle read/write logic, >> and done as two 8-byte cycles to qemu. This would avoid bloating the ioreq >> structure that communicates to qemu. > Are you proposing we do this for 4.3? I'm not sure how big that change > would be in terms of impact (just that one instruction, any 16 byte > operand?). > > Of course even if we did this for 4.3 we don't know what the next issue > will be with QXL. > > Ian. Furthermore, AVX instruction emulation would require support for 32byte operands. I don't see the multi-cycle logic scaling sensibly. ~Andrew > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > http://lists.xen.org/xen-devel