Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756872Ab3EOKVP (ORCPT ); Wed, 15 May 2013 06:21:15 -0400 Received: from smtp02.citrix.com ([66.165.176.63]:49357 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754960Ab3EOKVN (ORCPT ); Wed, 15 May 2013 06:21:13 -0400 X-IronPort-AV: E=Sophos;i="4.87,677,1363132800"; d="scan'208";a="24132021" Message-ID: <1368613266.11138.10.camel@hastur.hellion.org.uk> Subject: Re: [Xen-devel] [PATCH-v2] xen: Don't call arch_trigger_all_cpu_backtrace in dom0(pvm) From: Ian Campbell To: CC: Jan Beulich , xen-devel , Konrad Rzeszutek Wilk , "linux-kernel@vger.kernel.org" , Tamon Shiose , Feng Jin Date: Wed, 15 May 2013 11:21:06 +0100 In-Reply-To: <519349F1.8050607@oracle.com> References: <51610A25.4010301@oracle.com> <5162911202000078000CB38E@nat28.tlf.novell.com> <1365525374.17014.22.camel@zakaz.uk.xensource.com> <519349F1.8050607@oracle.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.4.4-3 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1848 Lines: 38 On Wed, 2013-05-15 at 16:40 +0800, Zhenzhong Duan wrote: > On 2013-04-10 00:36, Ian Campbell wrote: > > On Mon, 2013-04-08 at 08:42 +0100, Jan Beulich wrote: > >>>>> On 07.04.13 at 07:54, Zhenzhong Duan wrote: > >>> nmi isn't supported in dom0, fallback to general all cpu backtrace code. > >> Since when is sending NMIs not supported, and since when is this > >> Dom0-specific? If you want to deal with this, you should do so > >> properly: Special case sending NMIs in the respective Xen specific > >> code (using VCPUOP_send_nmi), and carry this out in a way not > >> dependent upon running (un)privileged. > > You'd also need to implement the upcall support for receiving NMIs, > > which IIRC isn't yet done for pvops. > Hi Ian, > > Could you give a suggestion on which file to change to support NMI upcall? > I compare with vMCE code, made similar change. > Use VCPUOP_send_nmi to send nmi between pvm guest vcpus, but nmi isn't > triggered. You need to register a callback with CALLBACKOP_register CALLBACKTYPE_nmi. You also need to write the code in entry.S to receive that callback. IIRC you also need to arrange that returning from an NMI is always done with HYPERVISOR_iret and not optimised to a direct iret as it can be otherwise. This is to allow the hypervisor to implement NMI masking correctly. The linux-2.6.18-xen.hg tree implements NMI callbacks so you may find inspiration there, although how upstreamable that approach is I'm not sure. In particular stealing a EFLAGS bit to force the HYPERVISOR_iret is certain to not be acceptable upstream. Ian. -- 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/