Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753564AbbEAKiA (ORCPT ); Fri, 1 May 2015 06:38:00 -0400 Received: from smtp02.citrix.com ([66.165.176.63]:40321 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751270AbbEAKh5 (ORCPT ); Fri, 1 May 2015 06:37:57 -0400 X-IronPort-AV: E=Sophos;i="5.13,350,1427760000"; d="scan'208";a="260655497" Message-ID: <55435782.3040506@citrix.com> Date: Fri, 1 May 2015 11:37:54 +0100 From: David Vrabel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.4.0 MIME-Version: 1.0 To: Boris Ostrovsky , , , , , CC: , , , Subject: Re: [Xen-devel] [PATCH] hypervisor/x86/xen: Unset X86_BUG_SYSRET_SS_ATTRS on Xen PV guests References: <1430420925-20474-1-git-send-email-boris.ostrovsky@oracle.com> In-Reply-To: <1430420925-20474-1-git-send-email-boris.ostrovsky@oracle.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-DLP: MIA2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1003 Lines: 23 On 30/04/15 20:08, Boris Ostrovsky wrote: > Commit 61f01dd941ba ("x86_64, asm: Work around AMD SYSRET SS descriptor > attribute issue") makes AMD processors set SS to __KERNEL_DS in > __switch_to() to deal with cases when SS is NULL. > > This breaks Xen PV guests who do not want to load SS with__KERNEL_DS. > > Since the problem that the commit is trying to address would have to be > fixed in the hypervisor (if it in fact exists under Xen) there is no > reason to set X86_BUG_SYSRET_SS_ATTRS flag for PV VPCUs here. > > This can be easily achieved by adding x86_hyper_xen_hvm.set_cpu_features > op which will clear this flag. (And since this structure is no longer > HVM-specific we should do some renaming). Applied to for-linus-4.1b, thanks. David -- 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/