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[83.42.66.122]) by smtp.gmail.com with ESMTPSA id f7sm43283wml.35.2021.07.21.07.01.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 21 Jul 2021 07:01:32 -0700 (PDT) Subject: Re: [PATCH v3] failover: unregister ROM on unplug To: "Dr. David Alan Gilbert" , Juan Quintela References: <20210721093955.225759-1-lvivier@redhat.com> <87tukneqdi.fsf@secure.mitica> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: <494e9441-6c05-da11-93a6-c9359b54d865@redhat.com> Date: Wed, 21 Jul 2021 16:01:30 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=philmd@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=philmd@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.459, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.117, 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: , Cc: Laurent Vivier , "Michael S. Tsirkin" , Jason Wang , qemu-devel@nongnu.org, Igor Mammedov , Jens Freimann Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 7/21/21 3:45 PM, Dr. David Alan Gilbert wrote: > * Juan Quintela (quintela@redhat.com) wrote: >> "Dr. David Alan Gilbert" wrote: >>> * Laurent Vivier (lvivier@redhat.com) wrote: >>>> The intend of failover is to allow to migrate a VM with a VFIO >>>> networking card without disrupting the network operation by switching >>>> to a virtio-net device during the migration. >>>> >>>> This simple change allows to test failover with a simulated device >>>> like e1000e rather than a vfio device, even if it's useless in real >>>> life it can help to debug failover. >>>> >>>> This is interesting to developers that want to test failover on >>>> a system with no vfio device. Moreover it simplifies host networking >>>> configuration as we can use the same bridge for virtio-net and >>>> the other failover networking device. >>>> >>>> Without this change the migration of a system configured with failover >>>> fails with: >>>> >>>> ... >>>> -device virtio-net-pci,id=virtionet0,failover=on,... \ >>>> -device e1000,failover_pair_id=virtionet0,... \ >>>> ... >>>> >>>> (qemu) migrate ... >>>> >>>> Unknown ramblock "0000:00:01.1:00.0/e1000e.rom", cannot accept migration >>>> error while loading state for instance 0x0 of device 'ram' >>>> load of migration failed: Invalid argument >>>> >>>> This happens because QEMU correctly unregisters the interface vmstate but >>>> not the ROM one. This patch fixes that. >>>> >>>> Signed-off-by: Laurent Vivier >>>> --- >>>> >>>> Notes: >>>> v3: >>>> remove useless space before comma >>>> >>>> v2: >>>> reset has_rom to false >>>> update commit log message >>>> >>>> hw/net/virtio-net.c | 4 ++++ >>>> 1 file changed, 4 insertions(+) >>>> >>>> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c >>>> index 16d20cdee52a..c0c2ec1ebb98 100644 >>>> --- a/hw/net/virtio-net.c >>>> +++ b/hw/net/virtio-net.c >>>> @@ -3256,6 +3256,10 @@ static void virtio_net_handle_migration_primary(VirtIONet *n, MigrationState *s) >>>> if (migration_in_setup(s) && !should_be_hidden) { >>>> if (failover_unplug_primary(n, dev)) { >>>> vmstate_unregister(VMSTATE_IF(dev), qdev_get_vmsd(dev), dev); >>>> + if (PCI_DEVICE(dev)->has_rom) { >>>> + PCI_DEVICE(dev)->has_rom = false; >>>> + vmstate_unregister_ram(&PCI_DEVICE(dev)->rom, dev); >>>> + } >>> >>> Not actually originated by your fix, but.... >>> >>> Why doesn't failover_replug_primary re-add the vmstates? >> >> Because we can't migrate until the "unplug" has happened. >> Yes, it is a mess. > > But if the migrate fails, shouldn't it add it back? > > Dave > >> I think this is the saner patch that I can think of for that >> functionality. >> >> What I wonder is why we register rom as ram, but I guess that the rom >> can be updated from userspace, or who knows. Unlikely, and if we can, this is a bug. We call memory_region_init_rom() in pci_add_option_rom(). * memory_region_init_rom: Initialize a ROM memory region. * * This has the same effect as calling memory_region_init_ram() * and then marking the resulting region read-only with * memory_region_set_readonly(). This includes arranging for the * contents to be migrated. I agree it would be clearer to have a vmstate_unregister_rom() function internally calling vmstate_unregister_ram(). >> >> Later, Juan. >> >>> (I did wonder if passing rom-file="" to the e1000 would help in your >>> testing case, but it still creates the RAM image). >>> >>> Dave >>> >>>> qapi_event_send_unplug_primary(dev->id); >>>> qatomic_set(&n->failover_primary_hidden, true); >>>> } else { >>>> -- >>>> 2.31.1 >>>> >>