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([2a01:e0a:280:24f0:9db0:474c:ff43:9f5c]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43bdd8c3aa8sm21251195e9.14.2025.03.06.06.26.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 06 Mar 2025 06:26:57 -0800 (PST) Message-ID: <7eb4dd80-0ae3-4522-bd1d-b004c19c4bf2@redhat.com> Date: Thu, 6 Mar 2025 15:26:55 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 30/36] vfio/migration: Multifd device state transfer support - send side To: Avihai Horon , "Maciej S. Szmigiero" , Peter Xu , Fabiano Rosas Cc: Alex Williamson , Eric Blake , Markus Armbruster , =?UTF-8?Q?Daniel_P_=2E_Berrang=C3=A9?= , Joao Martins , qemu-devel@nongnu.org References: <4d727e2e0435e0022d50004e474077632830e08d.1741124640.git.maciej.szmigiero@oracle.com> <629dff3c-865d-47d9-a01a-d212dfed1efb@nvidia.com> <97b87f22-b867-4282-ba13-efba16458859@maciej.szmigiero.name> <973268d4-85d6-4a17-ae76-2d20d8cfd7cb@redhat.com> <498a07aa-d539-46e6-90e9-8c41a59a6b2f@maciej.szmigiero.name> Content-Language: en-US, fr From: =?UTF-8?Q?C=C3=A9dric_Le_Goater?= Autocrypt: addr=clg@redhat.com; keydata= xsFNBFu8o3UBEADP+oJVJaWm5vzZa/iLgpBAuzxSmNYhURZH+guITvSySk30YWfLYGBWQgeo 8NzNXBY3cH7JX3/a0jzmhDc0U61qFxVgrPqs1PQOjp7yRSFuDAnjtRqNvWkvlnRWLFq4+U5t yzYe4SFMjFb6Oc0xkQmaK2flmiJNnnxPttYwKBPd98WfXMmjwAv7QfwW+OL3VlTPADgzkcqj 53bfZ4VblAQrq6Ctbtu7JuUGAxSIL3XqeQlAwwLTfFGrmpY7MroE7n9Rl+hy/kuIrb/TO8n0 ZxYXvvhT7OmRKvbYuc5Jze6o7op/bJHlufY+AquYQ4dPxjPPVUT/DLiUYJ3oVBWFYNbzfOrV RxEwNuRbycttMiZWxgflsQoHF06q/2l4ttS3zsV4TDZudMq0TbCH/uJFPFsbHUN91qwwaN/+ gy1j7o6aWMz+Ib3O9dK2M/j/O/Ube95mdCqN4N/uSnDlca3YDEWrV9jO1mUS/ndOkjxa34ia 70FjwiSQAsyIwqbRO3CGmiOJqDa9qNvd2TJgAaS2WCw/TlBALjVQ7AyoPEoBPj31K74Wc4GS Rm+FSch32ei61yFu6ACdZ12i5Edt+To+hkElzjt6db/UgRUeKfzlMB7PodK7o8NBD8outJGS tsL2GRX24QvvBuusJdMiLGpNz3uqyqwzC5w0Fd34E6G94806fwARAQABzSJDw6lkcmljIExl IEdvYXRlciA8Y2xnQHJlZGhhdC5jb20+wsGRBBMBCAA7FiEEoPZlSPBIlev+awtgUaNDx8/7 7KEFAmTLlVECGwMFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AACgkQUaNDx8/77KG0eg// S0zIzTcxkrwJ/9XgdcvVTnXLVF9V4/tZPfB7sCp8rpDCEseU6O0TkOVFoGWM39sEMiQBSvyY lHrP7p7E/JYQNNLh441MfaX8RJ5Ul3btluLapm8oHp/vbHKV2IhLcpNCfAqaQKdfk8yazYhh EdxTBlzxPcu+78uE5fF4wusmtutK0JG0sAgq0mHFZX7qKG6LIbdLdaQalZ8CCFMKUhLptW71 xe+aNrn7hScBoOj2kTDRgf9CE7svmjGToJzUxgeh9mIkxAxTu7XU+8lmL28j2L5uNuDOq9vl hM30OT+pfHmyPLtLK8+GXfFDxjea5hZLF+2yolE/ATQFt9AmOmXC+YayrcO2ZvdnKExZS1o8 VUKpZgRnkwMUUReaF/mTauRQGLuS4lDcI4DrARPyLGNbvYlpmJWnGRWCDguQ/LBPpbG7djoy k3NlvoeA757c4DgCzggViqLm0Bae320qEc6z9o0X0ePqSU2f7vcuWN49Uhox5kM5L86DzjEQ RHXndoJkeL8LmHx8DM+kx4aZt0zVfCHwmKTkSTQoAQakLpLte7tWXIio9ZKhUGPv/eHxXEoS 0rOOAZ6np1U/xNR82QbF9qr9TrTVI3GtVe7Vxmff+qoSAxJiZQCo5kt0YlWwti2fFI4xvkOi V7lyhOA3+/3oRKpZYQ86Frlo61HU3r6d9wzOwU0EW7yjdQEQALyDNNMw/08/fsyWEWjfqVhW pOOrX2h+z4q0lOHkjxi/FRIRLfXeZjFfNQNLSoL8j1y2rQOs1j1g+NV3K5hrZYYcMs0xhmrZ KXAHjjDx7FW3sG3jcGjFW5Xk4olTrZwFsZVUcP8XZlArLmkAX3UyrrXEWPSBJCXxDIW1hzwp bV/nVbo/K9XBptT/wPd+RPiOTIIRptjypGY+S23HYBDND3mtfTz/uY0Jytaio9GETj+fFis6 TxFjjbZNUxKpwftu/4RimZ7qL+uM1rG1lLWc9SPtFxRQ8uLvLOUFB1AqHixBcx7LIXSKZEFU CSLB2AE4wXQkJbApye48qnZ09zc929df5gU6hjgqV9Gk1rIfHxvTsYltA1jWalySEScmr0iS YBZjw8Nbd7SxeomAxzBv2l1Fk8fPzR7M616dtb3Z3HLjyvwAwxtfGD7VnvINPbzyibbe9c6g LxYCr23c2Ry0UfFXh6UKD83d5ybqnXrEJ5n/t1+TLGCYGzF2erVYGkQrReJe8Mld3iGVldB7 JhuAU1+d88NS3aBpNF6TbGXqlXGF6Yua6n1cOY2Yb4lO/mDKgjXd3aviqlwVlodC8AwI0Sdu jWryzL5/AGEU2sIDQCHuv1QgzmKwhE58d475KdVX/3Vt5I9kTXpvEpfW18TjlFkdHGESM/Jx IqVsqvhAJkalABEBAAHCwV8EGAECAAkFAlu8o3UCGwwACgkQUaNDx8/77KEhwg//WqVopd5k 8hQb9VVdk6RQOCTfo6wHhEqgjbXQGlaxKHoXywEQBi8eULbeMQf5l4+tHJWBxswQ93IHBQjK yKyNr4FXseUI5O20XVNYDJZUrhA4yn0e/Af0IX25d94HXQ5sMTWr1qlSK6Zu79lbH3R57w9j hQm9emQEp785ui3A5U2Lqp6nWYWXz0eUZ0Tad2zC71Gg9VazU9MXyWn749s0nXbVLcLS0yop s302Gf3ZmtgfXTX/W+M25hiVRRKCH88yr6it+OMJBUndQVAA/fE9hYom6t/zqA248j0QAV/p LHH3hSirE1mv+7jpQnhMvatrwUpeXrOiEw1nHzWCqOJUZ4SY+HmGFW0YirWV2mYKoaGO2YBU wYF7O9TI3GEEgRMBIRT98fHa0NPwtlTktVISl73LpgVscdW8yg9Gc82oe8FzU1uHjU8b10lU XOMHpqDDEV9//r4ZhkKZ9C4O+YZcTFu+mvAY3GlqivBNkmYsHYSlFsbxc37E1HpTEaSWsGfA HQoPn9qrDJgsgcbBVc1gkUT6hnxShKPp4PlsZVMNjvPAnr5TEBgHkk54HQRhhwcYv1T2QumQ izDiU6iOrUzBThaMhZO3i927SG2DwWDVzZltKrCMD1aMPvb3NU8FOYRhNmIFR3fcalYr+9gD uVKe8BVz4atMOoktmt0GWTOC8P4= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=clg@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 3/6/25 15:23, Avihai Horon wrote: > > On 06/03/2025 16:13, Maciej S. Szmigiero wrote: >> External email: Use caution opening links or attachments >> >> >> On 6.03.2025 14:37, Avihai Horon wrote: >>> >>> On 06/03/2025 12:32, Cédric Le Goater wrote: >>>> External email: Use caution opening links or attachments >>>> >>>> >>>> On 3/6/25 11:15, Maciej S. Szmigiero wrote: >>>>> On 6.03.2025 07:47, Avihai Horon wrote: >>>>>> >>>>>> On 05/03/2025 0:03, Maciej S. Szmigiero wrote: >>>>>>> External email: Use caution opening links or attachments >>>>>>> >>>>>>> >>>>>>> From: "Maciej S. Szmigiero" >>>>>>> >>>>>>> Implement the multifd device state transfer via additional per-device >>>>>>> thread inside save_live_complete_precopy_thread handler. >>>>>>> >>>>>>> Switch between doing the data transfer in the new handler and doing it >>>>>>> in the old save_state handler depending if VFIO multifd transfer is enabled >>>>>>> or not. >>>>>>> >>>>>>> Signed-off-by: Maciej S. Szmigiero >>>>>>> --- >>>>>>>   hw/vfio/migration-multifd.c   | 142 ++++++++++++++++++++++++++++++++++ >>>>>>>   hw/vfio/migration-multifd.h   |   6 ++ >>>>>>>   hw/vfio/migration.c           |  22 ++++-- >>>>>>>   hw/vfio/trace-events          |   2 + >>>>>>>   include/hw/vfio/vfio-common.h |   6 ++ >>>>>>>   5 files changed, 172 insertions(+), 6 deletions(-) >>>>>>> >>>>>>> diff --git a/hw/vfio/migration-multifd.c b/hw/vfio/migration-multifd.c >>>>>>> index 1d81233c755f..bfb9a72fa450 100644 >>>>>>> --- a/hw/vfio/migration-multifd.c >>>>>>> +++ b/hw/vfio/migration-multifd.c >>>>>>> @@ -496,6 +496,148 @@ bool vfio_multifd_setup(VFIODevice *vbasedev, bool alloc_multifd, Error **errp) >>>>>>>       return true; >>>>>>>   } >>>>>>> >>>>>>> +void vfio_multifd_emit_dummy_eos(VFIODevice *vbasedev, QEMUFile *f) >>>>>>> +{ >>>>>>> +    assert(vfio_multifd_transfer_enabled(vbasedev)); >>>>>>> + >>>>>>> +    /* >>>>>>> +     * Emit dummy NOP data on the main migration channel since the actual >>>>>>> +     * device state transfer is done via multifd channels. >>>>>>> +     */ >>>>>>> +    qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE); >>>>>>> +} >>>>>>> + >>>>>>> +static bool >>>>>>> +vfio_save_complete_precopy_thread_config_state(VFIODevice *vbasedev, >>>>>>> +                                               char *idstr, >>>>>>> +                                               uint32_t instance_id, >>>>>>> +                                               uint32_t idx, >>>>>>> +                                               Error **errp) >>>>>>> +{ >>>>>>> +    g_autoptr(QIOChannelBuffer) bioc = NULL; >>>>>>> +    g_autoptr(QEMUFile) f = NULL; >>>>>>> +    int ret; >>>>>>> +    g_autofree VFIODeviceStatePacket *packet = NULL; >>>>>>> +    size_t packet_len; >>>>>>> + >>>>>>> +    bioc = qio_channel_buffer_new(0); >>>>>>> +    qio_channel_set_name(QIO_CHANNEL(bioc), "vfio-device-config-save"); >>>>>>> + >>>>>>> +    f = qemu_file_new_output(QIO_CHANNEL(bioc)); >>>>>>> + >>>>>>> +    if (vfio_save_device_config_state(f, vbasedev, errp)) { >>>>>>> +        return false; >>>>>>> +    } >>>>>>> + >>>>>>> +    ret = qemu_fflush(f); >>>>>>> +    if (ret) { >>>>>>> +        error_setg(errp, "%s: save config state flush failed: %d", >>>>>>> +                   vbasedev->name, ret); >>>>>>> +        return false; >>>>>>> +    } >>>>>>> + >>>>>>> +    packet_len = sizeof(*packet) + bioc->usage; >>>>>>> +    packet = g_malloc0(packet_len); >>>>>>> +    packet->version = VFIO_DEVICE_STATE_PACKET_VER_CURRENT; >>>>>>> +    packet->idx = idx; >>>>>>> +    packet->flags = VFIO_DEVICE_STATE_CONFIG_STATE; >>>>>> >>>>>> The packet is sent on the wire. >>>>>> Shouldn't we use cpu_to_be32() for version, idx and flags? Also below in vfio_multifd_save_complete_precopy_thread(). >>>>>> And then use be32_to_cpu() in patch #26 when receiving the packet? >>>>> >>>>> Is it even possible to migrate to a host with different endianess here? >>>>> >>>>> Also AFAIK big endian hosts barely exist today, is any of them even VFIO-capable? >>>> >>>> s390x is VFIO capable. VFIO PCI migration is not supported on these. >>>> >>> It is indeed a niche use case and not even applicable today, but if we want to add support for it after the release, we will have to add a compatibility option for older QEMUs. >>> If we add support for it now, then we can avoid the compatibility option. >>> >>> It's a really small change and it can come even after the series is merged, as a fix. >>> So IMHO it wouldn't hurt, for completeness. >> >> For sure, any such bit stream change will need re-testing the whole VFIO migration. >> >> But I will be testing the queued buffers size limit anyway so it would make >> sense to test both at the same time. >> >> Wouldn't it make more sense, however, to squash this endianess change already >> to the relevant patches rather than to have such bit stream modifying patch on the top? >> >> It would help prevent backporting mistakes - when someone forgets about this last patch >> and ends with a different bit stream. > > I agree. > Whatever you and Cedric decide. > PR was sent. So it will be a "Fixes" patch. Thanks, C.