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bh=LKl/gz5OOFjHTKr3GsfcXouo3MUl5Qi7jz6OLT8dII0=; b=hJ3cDTrzqnlnjPULUo8YorZmvacsrem7M2Ia1lcvXYQ7btfXhdeOqb8zcAXKSmAqkRB0W/ W7po97ykU0jV940utP13aMtRJVwRK8zl4B0vXL0n6inVY8xp/E9cXimfKFjFUL8jxzZoug efvtIMTFK+pDRkPM+eA/HiPGNc6fE+4= 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-436-2wCZovHUNd-S9awpp42OkA-1; Wed, 17 Mar 2021 06:59:28 -0400 X-MC-Unique: 2wCZovHUNd-S9awpp42OkA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E57059CC00; Wed, 17 Mar 2021 10:59:26 +0000 (UTC) Received: from [10.64.54.49] (vpn2-54-49.bne.redhat.com [10.64.54.49]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 26DAA5D9C0; Wed, 17 Mar 2021 10:59:20 +0000 (UTC) Subject: Re: [PATCH] hw/char/pl011: Fix clock migration failure To: Peter Maydell References: <20210317044441.112313-1-gshan@redhat.com> <73a30558-469e-8ef0-02b2-aaaaa2449cda@redhat.com> From: Gavin Shan Message-ID: <3e7ba090-c45e-8fa4-1a59-16856241cbdc@redhat.com> Date: Wed, 17 Mar 2021 21:59:17 +1100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.0 MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=gshan@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=gshan@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.251, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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: , Reply-To: Gavin Shan Cc: Luc Michel , QEMU Developers , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , qemu-arm , Shan Gavin , Paolo Bonzini , =?UTF-8?Q?Marc-Andr=c3=a9_Lureau?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Peter, On 3/17/21 9:40 PM, Peter Maydell wrote: > On Wed, 17 Mar 2021 at 10:37, Gavin Shan wrote: >> On 3/17/21 8:09 PM, Peter Maydell wrote: >>> On Wed, 17 Mar 2021 at 04:44, Gavin Shan wrote: >>>> >>>> static const VMStateDescription vmstate_pl011 = { >>>> .name = "pl011", >>>> .version_id = 2, >>>> .minimum_version_id = 2, >>>> + .post_load = pl011_post_load, >>>> .fields = (VMStateField[]) { >>>> VMSTATE_UINT32(readbuff, PL011State), >>>> VMSTATE_UINT32(flags, PL011State), >>>> @@ -355,10 +355,6 @@ static const VMStateDescription vmstate_pl011 = { >>>> VMSTATE_INT32(read_trigger, PL011State), >>>> VMSTATE_END_OF_LIST() >>>> }, >>>> - .subsections = (const VMStateDescription * []) { >>>> - &vmstate_pl011_clock, >>>> - NULL >>>> - } >>>> }; >>> >>> Doesn't dropping the subsection break migration compat ? >>> >> >> It's why this patch needs to be backported to stable branches. >> In that way, we won't have migration compatible issue. > > No, migration has to work from the existing already > shipped 5.1, 5.2, etc releases to 6.0 (assuming you use > the correct "virt-5.2" &c versioned machine type.) > Commit aac63e0e6ea3 ("hw/char/pl011: add a clock input") is merged to v5.2.0. The migration failure happens during migration from v6.0 to v5.1 with machine type as "virt-5.1", instead of migrating from v5.1 to v6.0. One question is if we need support backwards migration? If we do support backwards migration, I think there are two options: (1) merge this patch and backport it to v5.2+; (2) Backport commit aac63e0e6ea3 to v5.2-. I guess (1) would be right way to go because it's less effort than (2). Besides, the clock needn't to be migrated if I'm correct. Thanks, Gavin