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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> Content-Language: en-US From: Avihai Horon In-Reply-To: <973268d4-85d6-4a17-ae76-2d20d8cfd7cb@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: FR0P281CA0042.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:48::9) To BL0PR12MB5538.namprd12.prod.outlook.com (2603:10b6:208:1c9::11) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL0PR12MB5538:EE_|CY8PR12MB7537:EE_ X-MS-Office365-Filtering-Correlation-Id: ca80e8dc-df9f-4a2c-4e53-08dd5cb3fe80 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|7416014|376014; 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envelope-from=avihaih@nvidia.com; helo=NAM11-DM6-obe.outbound.protection.outlook.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, SPF_HELO_PASS=-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 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. Thanks.