From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andre Przywara Subject: Re: mmx sse emulation Date: Wed, 5 Nov 2008 10:59:09 +0100 Message-ID: <49116E6D.9080408@amd.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Ashish Bijlani Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org Ashish Bijlani wrote: > Hi, > > I want to emulate mmx/sse for hvm guests when applications inside hvm > guests are compiled for mmx/sse but the underlying hardware doesn't > support mmx/sse. First: HVM guests require a virtualization capable processor. AFAIK all these processors support at least SSE2 (if not SSE3). So why do you want to emulate these instructions? Second: Applications should check the CPUID bit before using instruction set extension. So, if the host processor does not support MMX/SSE, the guest shouldn't see this bit, too. And I doubt that you are faster with emulating SSE compared to legacy x87-FPU executed natively. So, what is the use-case of your proposal? Or am I missing something here? Regards, Andre. > What is the best place to do this? i'm looking at > x86_emulate but i dunno if that is the best place to put the emulation > layer. any suggestions?? also, currently movq emulation is present in > x86_emulate for handling mmio. however, i realized that get_fpu fails > if the hardware doesn't have mmx capability. is it true or am i > missing something here? > > Thanks, > Ashish -- Andre Przywara AMD-OSRC (Dresden) Tel: x84917