From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760148Ab0EDSQc (ORCPT ); Tue, 4 May 2010 14:16:32 -0400 Received: from mga01.intel.com ([192.55.52.88]:9627 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759678Ab0EDSQa (ORCPT ); Tue, 4 May 2010 14:16:30 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.52,328,1270450800"; d="scan'208";a="564069138" Subject: Re: [PATCH 1/2] x86: eliminate TS_XSAVE From: Suresh Siddha Reply-To: Suresh Siddha To: Avi Kivity Cc: "H. Peter Anvin" , Brian Gerst , "Cui, Dexuan" , Sheng Yang , Ingo Molnar , "linux-kernel@vger.kernel.org" , "kvm@vger.kernel.org" In-Reply-To: <4BDFCF9F.3030600@redhat.com> References: <1272812038-32484-1-git-send-email-avi@redhat.com> <1272812038-32484-2-git-send-email-avi@redhat.com> <4BDDBA18.3080909@redhat.com> <4BDF4407.8000503@zytor.com> <4BDFCF9F.3030600@redhat.com> Content-Type: text/plain Organization: Intel Corp Date: Tue, 04 May 2010 11:15:27 -0700 Message-Id: <1272996927.2833.13.camel@sbs-t61.sc.intel.com> Mime-Version: 1.0 X-Mailer: Evolution 2.26.3 (2.26.3-1.fc11) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2010-05-04 at 00:41 -0700, Avi Kivity wrote: > On 05/04/2010 12:45 AM, H. Peter Anvin wrote: > > > >> I was trying to avoid a performance regression relative to the current > >> code, as it appears that some care was taken to avoid the memory reference. > >> > >> I agree that it's probably negligible compared to the save/restore > >> code. If the x86 maintainers agree as well, I'll replace it with > >> cpu_has_xsave. > >> > >> > > I asked Suresh to comment on this, since he wrote the original code. He > > did confirm that the intent was to avoid a global memory reference. > > > > > > Ok, so you're happy with the patch as is? As use_xsave() is in the hot context switch path, I would like to go with Avi's proposal. thanks, suresh