From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:59589) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QWoF0-0000RF-5W for qemu-devel@nongnu.org; Wed, 15 Jun 2011 07:26:35 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QWoEz-0003Ml-6i for qemu-devel@nongnu.org; Wed, 15 Jun 2011 07:26:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:7882) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QWoEy-0003MY-Ul for qemu-devel@nongnu.org; Wed, 15 Jun 2011 07:26:33 -0400 Message-ID: <4DF896D8.2000506@redhat.com> Date: Wed, 15 Jun 2011 14:26:16 +0300 From: Avi Kivity MIME-Version: 1.0 References: <4DF33413.9070605@web.de> <4DF5CE2E.50008@redhat.com> <4DF6FB62.60705@web.de> <4DF87717.9090007@redhat.com> <4DF88773.3050401@web.de> In-Reply-To: <4DF88773.3050401@web.de> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH][uq/master] kvm: x86: Save/restore FPU OP, IP and DP List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jan Kiszka Cc: Christophe Fergeau , Marcelo Tosatti , qemu-devel , kvm , Stefan Hajnoczi On 06/15/2011 01:20 PM, Jan Kiszka wrote: > > > > So fopcode will usually be clear. > > > > OK. So if bit 2 of IA32_MISC_ENABLE MSR, we must save that fields. But > if it's off, how to test for that other condition "last non-transparent > FP instruction ... had an unmasked exception" from the host? > We save fopcode unconditionally. But if IA32_MISC_ENABLE_MSR[2]=0, then fopcode will be zero, and we can skip the subsection (if the data and instruction pointers are also zero, which they will be). If it isn't zero, there's still a good chance fopcode will be zero (64-bit userspace, thread that hasn't used the fpu since the last context switch, last opcode happened to be zero). -- error compiling committee.c: too many arguments to function