Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755037Ab2E3OXm (ORCPT ); Wed, 30 May 2012 10:23:42 -0400 Received: from nat28.tlf.novell.com ([130.57.49.28]:58476 "EHLO nat28.tlf.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754844Ab2E3OXl convert rfc822-to-8bit (ORCPT ); Wed, 30 May 2012 10:23:41 -0400 Message-Id: <4FC649790200007800086E51@nat28.tlf.novell.com> X-Mailer: Novell GroupWise Internet Agent 12.0.0 Date: Wed, 30 May 2012 15:23:21 +0100 From: "Jan Beulich" To: "Andre Przywara" Cc: "Jacob Shin" , , , , , , , Subject: Re: [Xen-devel] [PATCH] x86/amd: fix crash as Xen Dom0 on AMD Trinity systems References: <1338383402-3838-1-git-send-email-andre.przywara@amd.com> <4FC63DAF0200007800086DC5@nat28.tlf.novell.com> <4FC62888.9010407@amd.com> In-Reply-To: <4FC62888.9010407@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1706 Lines: 38 >>> On 30.05.12 at 16:02, Andre Przywara wrote: > On 05/30/2012 03:33 PM, Jan Beulich wrote: >> Further, I can't see how checking_wrmsrl() is being paravirtualized >> any better than wrmsrl_amd_safe() - both have nothing but an >> exception handling fixup attached to the wrmsr invocation. Care >> to point out what actual crash it is that was seen? > > AFAIK, the difference is between the "l" and the regs version for > rd/wrmsr. We have a patch already here to fix this. Will send it out > soon. Jacob, can you comment on this? I see - the Xen code blindly overwrites pv_cpu_ops, despite not having initialized all members. That's an obvious oversight of the patch that introduced the _regs variants. Plus having secondary instances of things like rdmsrl_amd_safe() in asm/paravirt.h seems pretty strange an approach (which was why initially I didn't spot how a crash could happen there) - only the lowest level functions should get re-implemented here. >> Finally, I would question whether re-enabling the topology >> extensions under Xen shouldn't be skipped altogether, perhaps >> even on Dom0 (as the hypervisor is controlling this MSR, but in >> any case on DomU - the hypervisor won't allow (read: ignore, >> not fault on) the write anyway (and will log a message for each >> (v)CPU that attempts this). > > This is probably right. Let me think about this. I'll submit a respective hypervisor side patch soonish. Jan -- 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/