From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 898D4C33CB2 for ; Fri, 31 Jan 2020 09:39:50 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 558E520707 for ; Fri, 31 Jan 2020 09:39:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="BI/ZYDDp" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 558E520707 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:50602 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ixSmD-0006K9-JB for qemu-devel@archiver.kernel.org; Fri, 31 Jan 2020 04:39:49 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:38734) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ixSla-0005mF-NN for qemu-devel@nongnu.org; Fri, 31 Jan 2020 04:39:11 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ixSlZ-0004xX-CO for qemu-devel@nongnu.org; Fri, 31 Jan 2020 04:39:10 -0500 Received: from mail.kernel.org ([198.145.29.99]:56668) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ixSlW-0004v3-FK; Fri, 31 Jan 2020 04:39:06 -0500 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3033B20707; Fri, 31 Jan 2020 09:39:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1580463545; bh=Cp3p5SMGhrd94coYZ6hL8kIlAqY8MsSmw65mT3Rp2as=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=BI/ZYDDpJJWbuc7Y85nN1Snwv7KzQb6uJTo9RL1KK+7CzlFV2i1muQuW/UCbFA7Mg oGEXkyNxNvs0QmwjEVJ+6cGolrWaCXg0vLPOVhiLeD4cwjly3V+Ht9YqvXzaKaBjki lb2DsYr42lb2PPc/ipzZRVgdy8EnpfaONJQAN86g= Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1ixSlT-002Ki8-5g; Fri, 31 Jan 2020 09:39:03 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Date: Fri, 31 Jan 2020 09:39:03 +0000 From: Marc Zyngier To: Gavin Shan Subject: Re: [RFC PATCH] hw/arm/virt: Support NMI injection In-Reply-To: References: <20191219040612.28431-1-gshan@redhat.com> <7f6e29e6-1df9-4513-79ba-b53873b0735e@ozlabs.ru> <544f261e4b9c97f1d3a5fb64cef42ba5@kernel.org> Message-ID: X-Sender: maz@kernel.org User-Agent: Roundcube Webmail/1.3.8 X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: gshan@redhat.com, aik@ozlabs.ru, qemu-arm@nongnu.org, peter.maydell@linaro.org, pbonzini@redhat.com, drjones@redhat.com, eric.auger@redhat.com, jthierry@redhat.com, shan.gavin@gmail.com, qemu-devel@nongnu.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 198.145.29.99 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: peter.maydell@linaro.org, drjones@redhat.com, jthierry@redhat.com, Alexey Kardashevskiy , qemu-devel@nongnu.org, eric.auger@redhat.com, qemu-arm@nongnu.org, shan.gavin@gmail.com, pbonzini@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2020-01-31 06:59, Gavin Shan wrote: > On 1/29/20 8:04 PM, Marc Zyngier wrote: >> On 2020-01-29 02:44, Alexey Kardashevskiy wrote: >>> On 28/01/2020 17:48, Gavin Shan wrote: >>>> but a NMI is injected >>>> through LAPIC on x86. So I'm not sure what architect (system reset=20 >>>> on >>>> ppc or injecting NMI on x86) aarch64 should follow. >>>=20 >>> I'd say whatever triggers in-kernel debugger or kdump but I am not >>> familiar with ARM at all :) >>=20 >> All that is completely OS specific, and has no relation to the=20 >> architecture. >> As I mentioned in another part of the thread, the closest thing to=20 >> this >> would be to implement SDEI together with an IMPDEF mechanism to enter=20 >> it >> (or even generate a RAS error). >>=20 >> On the other hand, SDEI is pretty horrible, and means either KVM or=20 >> QEMU >> acting like a firmware for the guest. To say that I'm not keen is a=20 >> massive >> understatement. >>=20 >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 M. >=20 > Marc, could you please explain a bit about "IMPDEF mechanism"? I'm not=20 > sure if > it means a non-standard SDEI event should be used, corresponding to the= =20 > HMP/QMP > "nmi" command. SDEI doesn't quite describe *why* and *how* you enter it. You just get=20 there by some mean (SError, Group-0 interrupt, or IMPlementation DEFined=20 mechanism). It is then for the SDEI implementation to sort it out and enter the OS=20 using the registered entry point. > Also, If I'm correct, you agree that a crash dump should be triggered=20 > on arm64 > guest once HMP/QMP "nmi" command is issued? No, I don't agree. QEMU and KVM are OS agnostic, and there is nothing in=20 the ARMv8 architecture that talks about "crash dumps". If your "nmi" command=20 generates a SDEI event and that event gets dispatched to the guest, it is entirely=20 the guest's responsibility to do whatever it wants. We should stay clear of assuming=20 behaviours. > I also dig into SDEI a bit. It seems the SDEI support in QEMU isn't=20 > upstream yet: >=20 > https://patchew.org/QEMU/20191105091056.9541-1-guoheyi@huawei.com/ And I'm glad. SDEI, as I said, is absolutely horrible. I'm also very=20 fortunate to have been CC'd on this series on an email address I cannot read. This would have huge impacts on both QEMU and KVM, and this needs more=20 than a knee jerk reaction to support a QEMU command. And to be honest, if what you require is the guest kernel to panic, why=20 don't you just implement a QEMU-specific driver in Linux that does just that? Some kind of watchdog driver, maybe? Thanks, M. --=20 Jazz is not dead. It just smells funny...