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([2a01:e0a:165:d60:38c8:6df5:c9ca:a366]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38f2591570esm14445407f8f.59.2025.02.17.23.54.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 17 Feb 2025 23:54:28 -0800 (PST) Message-ID: <9f8b347f-64ab-44b9-a5ca-053ae239a484@redhat.com> Date: Tue, 18 Feb 2025 08:54:27 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 26/33] vfio/migration: Multifd device state transfer support - receive init/cleanup To: "Maciej S. Szmigiero" Cc: Alex Williamson , Fabiano Rosas , Peter Xu , Eric Blake , Markus Armbruster , =?UTF-8?Q?Daniel_P_=2E_Berrang=C3=A9?= , Avihai Horon , Joao Martins , qemu-devel@nongnu.org References: <1fcf182307e8e1f67a3c226e62d26cad3a2f60d0.1738171076.git.maciej.szmigiero@oracle.com> <6c337aec-d004-4ede-a86b-0c934b275fa9@redhat.com> <1ab2d96f-f37d-466e-83db-0e3d39581bc7@maciej.szmigiero.name> <319789d3-703a-4d4b-8d5a-f2a229666fad@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: <319789d3-703a-4d4b-8d5a-f2a229666fad@maciej.szmigiero.name> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.129.124; 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_H5=0.001, RCVD_IN_MSPIKE_WL=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 2/17/25 23:13, Maciej S. Szmigiero wrote: > On 17.02.2025 10:38, Cédric Le Goater wrote: >> On 2/14/25 21:55, Maciej S. Szmigiero wrote: >>> On 12.02.2025 11:55, Cédric Le Goater wrote: >>>> On 1/30/25 11:08, Maciej S. Szmigiero wrote: >>>>> From: "Maciej S. Szmigiero" >>>>> >>>>> Add support for VFIOMultifd data structure that will contain most of the >>>>> receive-side data together with its init/cleanup methods. >>>>> >>>>> Signed-off-by: Maciej S. Szmigiero >>>>> --- >>>>>   hw/vfio/migration.c           | 52 +++++++++++++++++++++++++++++++++-- >>>>>   include/hw/vfio/vfio-common.h |  5 ++++ >>>>>   2 files changed, 55 insertions(+), 2 deletions(-) >>>>> >>>>> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c >>>>> index 3211041939c6..bcdf204d5cf4 100644 >>>>> --- a/hw/vfio/migration.c >>>>> +++ b/hw/vfio/migration.c >>>>> @@ -300,6 +300,9 @@ typedef struct VFIOStateBuffer { >>>>>       size_t len; >>>>>   } VFIOStateBuffer; >>>>> +typedef struct VFIOMultifd { >>>>> +} VFIOMultifd; >>>>> + >>>>>   static void vfio_state_buffer_clear(gpointer data) >>>>>   { >>>>>       VFIOStateBuffer *lb = data; >>>>> @@ -398,6 +401,18 @@ static int vfio_load_device_config_state(QEMUFile *f, void *opaque) >>>>>       return qemu_file_get_error(f); >>>>>   } >>>>> +static VFIOMultifd *vfio_multifd_new(void) >>>>> +{ >>>>> +    VFIOMultifd *multifd = g_new(VFIOMultifd, 1); >>>>> + >>>>> +    return multifd; >>>>> +} >>>>> + >>>>> +static void vfio_multifd_free(VFIOMultifd *multifd) >>>>> +{ >>>>> +    g_free(multifd); >>>>> +} >>>>> + >>>>>   static void vfio_migration_cleanup(VFIODevice *vbasedev) >>>>>   { >>>>>       VFIOMigration *migration = vbasedev->migration; >>>>> @@ -785,14 +800,47 @@ static void vfio_save_state(QEMUFile *f, void *opaque) >>>>>   static int vfio_load_setup(QEMUFile *f, void *opaque, Error **errp) >>>>>   { >>>>>       VFIODevice *vbasedev = opaque; >>>>> +    VFIOMigration *migration = vbasedev->migration; >>>>> +    int ret; >>>>> + >>>>> +    /* >>>>> +     * Make a copy of this setting at the start in case it is changed >>>>> +     * mid-migration. >>>>> +     */ >>>>> +    if (vbasedev->migration_multifd_transfer == ON_OFF_AUTO_AUTO) { >>>>> +        migration->multifd_transfer = vfio_multifd_transfer_supported(); >>>> >>>> Attribute "migration->multifd_transfer" is not necessary. It can be >>>> replaced by a small inline helper testing pointer migration->multifd >>>> and this routine can use a local variable instead. >>> >>> It's necessary for the send side since it does not need/allocate VFIOMultifd >>> at migration->multifd, so this (receive) side can use it for commonality too. >> >> Hmm, we can allocate migration->multifd on the send side too, even >> if the attributes are unused and it is up to vfio_multifd_free() to >> make the difference between the send/recv side. > > Allocating an unnecessary VFIOMultifd structure that has 12 members, > some of them complex like QemuThread, QemuCond or QemuMutex, just > to avoid having one extra bool variable (migration_multifd_transfer or > whatever it ends being named) seem like a poor trade-off for me. > >> >> Something that is bothering me is the lack of introspection tools >> and statistics. What could be possibly added under VFIOMultifd and >> VfioStats ? > > There's already VFIO bytes transferred counter and also a > multifd bytes transferred counter. > > There are quite a few trace events (both existing and newly added > by this patch). > > While even more statistics and traces may help with tuning/debugging > in some cases that's something easily added in the future. > >>>> I don't think the '_transfer' suffix adds much to the understanding. >>> >>> The migration->multifd was already taken by VFIOMultifd struct, but >>> it could use other name (migration->multifd_switch? migration->multifd_on?). >> >> yeah. Let's try to get rid of it first. >> >>>>> +    } else { >>>>> +        migration->multifd_transfer = >>>>> +            vbasedev->migration_multifd_transfer == ON_OFF_AUTO_ON; >>>>> +    } >>>>> + >>>>> +    if (migration->multifd_transfer && !vfio_multifd_transfer_supported()) { >>>>> +        error_setg(errp, >>>>> +                   "%s: Multifd device transfer requested but unsupported in the current config", >>>>> +                   vbasedev->name); >>>>> +        return -EINVAL; >>>>> +    } >>>> >>>> The above checks are also introduced in vfio_save_setup(). Please >>>> implement a common routine vfio_multifd_is_enabled() or some other >>>> name. >>> >>> Done (as common vfio_multifd_transfer_setup()). >> >> vfio_multifd_is_enabled() please, returning a bool. > > Functions named *_is_something() normally just check some conditions > and return a computed value without having any side effects. > > Here, vfio_multifd_transfer_setup() also sets migration->multifd_transfer > appropriately (or could migration->multifd) - that's common code for > save and load. > > I guess you meant to move something else rather than this block > of code into vfio_multifd_is_enabled() - see my answer below. > >>>>>       vfio_migration_cleanup(vbasedev); >>>>>       trace_vfio_load_cleanup(vbasedev->name); >>>>> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h >>>>> index 153d03745dc7..c0c9c0b1b263 100644 >>>>> --- a/include/hw/vfio/vfio-common.h >>>>> +++ b/include/hw/vfio/vfio-common.h >>>>> @@ -61,6 +61,8 @@ typedef struct VFIORegion { >>>>>       uint8_t nr; /* cache the region number for debug */ >>>>>   } VFIORegion; >>>>> +typedef struct VFIOMultifd VFIOMultifd; >>>>> + >>>>>   typedef struct VFIOMigration { >>>>>       struct VFIODevice *vbasedev; >>>>>       VMChangeStateEntry *vm_state; >>>>> @@ -72,6 +74,8 @@ typedef struct VFIOMigration { >>>>>       uint64_t mig_flags; >>>>>       uint64_t precopy_init_size; >>>>>       uint64_t precopy_dirty_size; >>>>> +    bool multifd_transfer; >>>>> +    VFIOMultifd *multifd; >>>>>       bool initial_data_sent; >>>>>       bool event_save_iterate_started; >>>>> @@ -133,6 +137,7 @@ typedef struct VFIODevice { >>>>>       bool no_mmap; >>>>>       bool ram_block_discard_allowed; >>>>>       OnOffAuto enable_migration; >>>>> +    OnOffAuto migration_multifd_transfer; >>>> >>>> This property should be added at the end of the series, with documentation, >>>> and used in the vfio_multifd_some_name() routine I mentioned above. >>>> >>> >>> The property behind this variable *is* in fact introduced at the end of the series - >>> in a commit called "vfio/migration: Add x-migration-multifd-transfer VFIO property" >>> after which there are only commits adding the related compat entry and a VFIO >>> developer doc update. >>> >>> The variable itself needs to be introduced earlier since various newly >>> introduced code blocks depend on its value to only get activated when multifd >>> transfer is enabled. >> >> Not if you introduce a vfio_multifd_is_enabled() routine hiding >> the details. In that case, the property and attribute can be added >> at the end of the series and you don't need to add the attribute >> earlier. > > The part above that you wanted to be moved into vfio_multifd_is_enabled() > is one-time check for load or save setup time. > > That's *not* the switch to be tested by other parts of the code > during the migration process to determine whether multifd transfer > is in use. > > If you want vfio_multifd_is_enabled() to be that switch that's tested by > other parts of the VFIO migration code then it will finally consist of > just a single line of code: > "return migration->multifd_transfer" (or "return migration->multifd"). > > Then indeed the variable could be introduced with the property than > controls it, but a dummy vfio_multifd_is_enabled() will need to be > introduced earlier as "return false" to not break the build. Sorry but I have switched to another series now, the one for live update, and I will recheck your v5 proposal. Thanks, C.