Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751389AbWERUXR (ORCPT ); Thu, 18 May 2006 16:23:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751391AbWERUXR (ORCPT ); Thu, 18 May 2006 16:23:17 -0400 Received: from mailout1.vmware.com ([65.113.40.130]:25092 "EHLO mailout1.vmware.com") by vger.kernel.org with ESMTP id S1751389AbWERUXR (ORCPT ); Thu, 18 May 2006 16:23:17 -0400 Message-ID: <446CD6FF.30409@vmware.com> Date: Thu, 18 May 2006 13:20:15 -0700 From: Zachary Amsden User-Agent: Thunderbird 1.5.0.2 (X11/20060420) MIME-Version: 1.0 To: Chris Wright Cc: linux-kernel@vger.kernel.org, virtualization@lists.osdl.org, xen-devel@lists.xensource.com, Ian Pratt , Christian Limpach Subject: Re: [RFC PATCH 17/35] Segment register changes for Xen References: <20060509084945.373541000@sous-sol.org> <20060509085154.802230000@sous-sol.org> In-Reply-To: <20060509085154.802230000@sous-sol.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 863 Lines: 23 Chris Wright wrote: > 1. We clear FS/GS before changing TLS entries and switching LDT, as > otherwise the hypervisor will fail to restore thread-local values on > return to the guest kernel and we take a slow exception path. > @@ -647,6 +647,8 @@ struct task_struct fastcall * __switch_t > */ > savesegment(fs, prev->fs); > savesegment(gs, prev->gs); > + clearsegment(fs); > + clearsegment(gs); > Really not needed. Think about it. You can even speed up Xen. I'm glad the native operation here is a nop, but it should be hypervisor_clearsegment or xen_clearsegment if you really want to keep it. Zach - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/