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=-5.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 E3CD2C2BB1D for ; Fri, 13 Mar 2020 13:58:49 +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 AFAF5206B7 for ; Fri, 13 Mar 2020 13:58:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="T1NisOOs" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AFAF5206B7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:59248 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jCkps-0001Hu-U7 for qemu-devel@archiver.kernel.org; Fri, 13 Mar 2020 09:58:48 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:38257) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jCkop-0004kU-JM for qemu-devel@nongnu.org; Fri, 13 Mar 2020 09:57:44 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jCkon-0004nJ-KN for qemu-devel@nongnu.org; Fri, 13 Mar 2020 09:57:42 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:22878 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1jCkon-0004lW-Fv for qemu-devel@nongnu.org; Fri, 13 Mar 2020 09:57:41 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1584107861; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=QAlmTJ7tPRbz8s4X0m3WQos73YY1d7yUlWG86efoHIs=; b=T1NisOOs6So1jRb8kWanyD5a0izUDxffG/0YxmDHfNPgeiogwuhTaYgpLgsImA6ZNCQbQf DKMUfPheO4qeL4EJtZK9nDrfuSbWOLz5SeWonxciyS2RioBLZSRlqZ+DeHFQRtUFmENlYX Bk6/DrU+cDS6e444Ygg1RVLxcciuuPs= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-126-s8cucU7OMGC8Odv7-lNR2A-1; Fri, 13 Mar 2020 09:57:37 -0400 X-MC-Unique: s8cucU7OMGC8Odv7-lNR2A-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B6E5F18C8C01; Fri, 13 Mar 2020 13:57:36 +0000 (UTC) Received: from work-vm (ovpn-117-92.ams2.redhat.com [10.36.117.92]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 73B7F8FBED; Fri, 13 Mar 2020 13:57:34 +0000 (UTC) Date: Fri, 13 Mar 2020 13:57:32 +0000 From: "Dr. David Alan Gilbert" To: Peter Maydell Subject: Re: [PATCH] exec/rom_reset: Free rom data during inmigrate skip Message-ID: <20200313135732.GE3581@work-vm> References: <20200313123014.206828-1-dgilbert@redhat.com> <20200313133451.GD3581@work-vm> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.13.3 (2020-01-12) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.120 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: Paolo Bonzini , Yan Vugenfirer , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , QEMU Developers Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Peter Maydell (peter.maydell@linaro.org) wrote: > On Fri, 13 Mar 2020 at 13:34, Dr. David Alan Gilbert > wrote: > > > > * Peter Maydell (peter.maydell@linaro.org) wrote: > > > On Fri, 13 Mar 2020 at 13:21, Peter Maydell wrote: > > > > > > > > On Fri, 13 Mar 2020 at 12:31, Dr. David Alan Gilbert (git) > > > > wrote: > > > > > > > > > > From: "Dr. David Alan Gilbert" > > > > > > > > > > Commit 355477f8c73e9 skips rom reset when we're an incoming migra= tion > > > > > so as not to overwrite shared ram in the ignore-shared migration > > > > > optimisation. > > > > > However, it's got an unexpected side effect that because it skips > > > > > freeing the ROM data, when rom_reset gets called later on, after > > > > > migration (e.g. during a reboot), the ROM does get reset to the o= riginal > > > > > file contents. Because of seabios/x86's weird reboot process > > > > > this confuses a reboot into hanging after a migration. > > > > > > > > > > Fixes: 355477f8c73e9 ("migration: do not rom_reset() during incom= ing migration") > > > > > https://bugzilla.redhat.com/show_bug.cgi?id=3D1809380 > > > > > > > > > > Signed-off-by: Dr. David Alan Gilbert > > > > > --- > > > > > hw/core/loader.c | 23 ++++++++++++++--------- > > > > > 1 file changed, 14 insertions(+), 9 deletions(-) > > > > > > > > > > > > > > QTAILQ_FOREACH(rom, &roms, next) { > > > > > if (rom->fw_file) { > > > > > continue; > > > > > } > > > > > + /* > > > > > + * We don't need to fill in the RAM with ROM data becaus= e we'll fill > > > > > + * the data in during the next incoming migration in all= cases. Note > > > > > + * that some of those RAMs can actually be modified by t= he guest on ARM > > > > > + * so this is probably the only right thing to do here. > > > > > + */ > > > > > + if (runstate_check(RUN_STATE_INMIGRATE) && rom->data) { > > > > > + /* > > > > > + * Free it so that a rom_reset after migration doesn= 't overwrite a > > > > > + * potentially modified 'rom'. > > > > > + */ > > > > > + rom_free_data(rom); > > > > > > > > Shouldn't this condition match the condition in rom_reset() > > > > for when we call rom_free_data()? You want the behaviour > > > > on a subsequent reset to match the behaviour you'd get > > > > if you did a reset on the source end without the migration. > > > > > > Wait, this *is* rom_reset(). Now I'm really confused. > > > > The exsiting rom_reset gets called multiple times: > > a) During init > > This actually copies the ROMs and then calls rom_free_data > > > > b) During a subsequent reboot > > This is mostly skipped because rom->data is now free because > > of the prior call to rom_free_data during (a) > > > > During an inbound migrate, (a) happens before the migration, and > > (b) happens during a reboot after the migration. > > > > The problem is that 355477f8c73e9 caused (a) to be skipped > > then when (b) happens it actually overwrites the ROM because > > the rom_free_data had been skipped. What I'm doing here is > > doing the rom_free_data(..) which causes it to then skip this > > iteration during (a) AND causes it to skip it during (b). >=20 > OK, but why is your condition for when to call rom_free_data() > in this special case not the same as the condition that we > use in the normal no-migration-involved case? I would expect > those to match up. Ah yes, I think you're right, so something like: if (runstate_check(RUN_STATE_INMIGRATE) && rom->data && rom->isrom) { I'll try that after lunch. Dave > thanks > -- PMM >=20 -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK