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([2a01:e0a:280:24f0:ecac:5b28:cd98:868a]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38dcaf3e4bcsm14854786f8f.41.2025.02.12.08.19.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 12 Feb 2025 08:19:01 -0800 (PST) Message-ID: <0fff5a27-7e52-4f00-af65-46f4cf025f4f@redhat.com> Date: Wed, 12 Feb 2025 17:19:00 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 28/33] vfio/migration: Multifd device state transfer support - load thread From: =?UTF-8?Q?C=C3=A9dric_Le_Goater?= To: "Maciej S. Szmigiero" , Peter Xu , Fabiano Rosas Cc: Alex Williamson , Eric Blake , Markus Armbruster , =?UTF-8?Q?Daniel_P_=2E_Berrang=C3=A9?= , Avihai Horon , Joao Martins , qemu-devel@nongnu.org References: <3e1708a19ab743441a4771a8868043887ea4543c.1738171076.git.maciej.szmigiero@oracle.com> Content-Language: en-US, fr 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: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.495, 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_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_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 2/12/25 16:48, Cédric Le Goater wrote: > On 1/30/25 11:08, Maciej S. Szmigiero wrote: >> From: "Maciej S. Szmigiero" >> >> Since it's important to finish loading device state transferred via the >> main migration channel (via save_live_iterate SaveVMHandler) before >> starting loading the data asynchronously transferred via multifd the thread >> doing the actual loading of the multifd transferred data is only started >> from switchover_start SaveVMHandler. >> >> switchover_start handler is called when MIG_CMD_SWITCHOVER_START >> sub-command of QEMU_VM_COMMAND is received via the main migration channel. >> >> This sub-command is only sent after all save_live_iterate data have already >> been posted so it is safe to commence loading of the multifd-transferred >> device state upon receiving it - loading of save_live_iterate data happens >> synchronously in the main migration thread (much like the processing of >> MIG_CMD_SWITCHOVER_START) so by the time MIG_CMD_SWITCHOVER_START is >> processed all the proceeding data must have already been loaded. >> >> Signed-off-by: Maciej S. Szmigiero >> --- >>   hw/vfio/migration.c  | 229 +++++++++++++++++++++++++++++++++++++++++++ >>   hw/vfio/trace-events |   5 + >>   2 files changed, 234 insertions(+) >> >> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c >> index 0c0caec1bd64..ab5b097f59c9 100644 >> --- a/hw/vfio/migration.c >> +++ b/hw/vfio/migration.c >> @@ -301,8 +301,16 @@ typedef struct VFIOStateBuffer { >>   } VFIOStateBuffer; >>   typedef struct VFIOMultifd { >> +    QemuThread load_bufs_thread; >> +    bool load_bufs_thread_running; >> +    bool load_bufs_thread_want_exit; >> + >> +    bool load_bufs_iter_done; >> +    QemuCond load_bufs_iter_done_cond; >> + >>       VFIOStateBuffers load_bufs; >>       QemuCond load_bufs_buffer_ready_cond; >> +    QemuCond load_bufs_thread_finished_cond; >>       QemuMutex load_bufs_mutex; /* Lock order: this lock -> BQL */ >>       uint32_t load_buf_idx; >>       uint32_t load_buf_idx_last; >> @@ -449,6 +457,171 @@ static bool vfio_load_state_buffer(void *opaque, char *data, size_t data_size, >>       return true; >>   } >> +static VFIOStateBuffer *vfio_load_state_buffer_get(VFIOMultifd *multifd) >> +{ >> +    VFIOStateBuffer *lb; >> +    guint bufs_len; >> + >> +    bufs_len = vfio_state_buffers_size_get(&multifd->load_bufs); >> +    if (multifd->load_buf_idx >= bufs_len) { >> +        assert(multifd->load_buf_idx == bufs_len); >> +        return NULL; >> +    } >> + >> +    lb = vfio_state_buffers_at(&multifd->load_bufs, >> +                               multifd->load_buf_idx); >> +    if (!lb->is_present) { >> +        return NULL; >> +    } >> + >> +    return lb; >> +} >> + >> +static int vfio_load_bufs_thread_load_config(VFIODevice *vbasedev) >> +{ >> +    return -EINVAL; >> +} >> + >> +static bool vfio_load_state_buffer_write(VFIODevice *vbasedev, >> +                                         VFIOStateBuffer *lb, >> +                                         Error **errp) >> +{ >> +    VFIOMigration *migration = vbasedev->migration; >> +    VFIOMultifd *multifd = migration->multifd; >> +    g_autofree char *buf = NULL; >> +    char *buf_cur; >> +    size_t buf_len; >> + >> +    if (!lb->len) { >> +        return true; >> +    } >> + >> +    trace_vfio_load_state_device_buffer_load_start(vbasedev->name, >> +                                                   multifd->load_buf_idx); >> + >> +    /* lb might become re-allocated when we drop the lock */ >> +    buf = g_steal_pointer(&lb->data); >> +    buf_cur = buf; >> +    buf_len = lb->len; >> +    while (buf_len > 0) { >> +        ssize_t wr_ret; >> +        int errno_save; >> + >> +        /* >> +         * Loading data to the device takes a while, >> +         * drop the lock during this process. >> +         */ >> +        qemu_mutex_unlock(&multifd->load_bufs_mutex); >> +        wr_ret = write(migration->data_fd, buf_cur, buf_len); >> +        errno_save = errno; >> +        qemu_mutex_lock(&multifd->load_bufs_mutex); >> + >> +        if (wr_ret < 0) { >> +            error_setg(errp, >> +                       "writing state buffer %" PRIu32 " failed: %d", >> +                       multifd->load_buf_idx, errno_save); >> +            return false; >> +        } >> + >> +        assert(wr_ret <= buf_len); >> +        buf_len -= wr_ret; >> +        buf_cur += wr_ret; >> +    } >> + >> +    trace_vfio_load_state_device_buffer_load_end(vbasedev->name, >> +                                                 multifd->load_buf_idx); >> + >> +    return true; >> +} >> + >> +static bool vfio_load_bufs_thread_want_abort(VFIOMultifd *multifd, >> +                                             bool *should_quit) >> +{ >> +    return multifd->load_bufs_thread_want_exit || qatomic_read(should_quit); >> +} > > _abort or _exit or _quit ? I would opt for vfio_load_bufs_thread_want_exit() > to match multifd->load_bufs_thread_want_exit. > > >> +static bool vfio_load_bufs_thread(void *opaque, bool *should_quit, Error **errp) >> +{ >> +    VFIODevice *vbasedev = opaque; >> +    VFIOMigration *migration = vbasedev->migration; >> +    VFIOMultifd *multifd = migration->multifd; >> +    bool ret = true; >> +    int config_ret; >> + >> +    assert(multifd); >> +    QEMU_LOCK_GUARD(&multifd->load_bufs_mutex); >> + >> +    assert(multifd->load_bufs_thread_running); >> + >> +    while (!vfio_load_bufs_thread_want_abort(multifd, should_quit)) { >> +        VFIOStateBuffer *lb; >> + >> +        assert(multifd->load_buf_idx <= multifd->load_buf_idx_last); >> + >> +        lb = vfio_load_state_buffer_get(multifd); >> +        if (!lb) { >> +            trace_vfio_load_state_device_buffer_starved(vbasedev->name, >> +                                                        multifd->load_buf_idx); >> +            qemu_cond_wait(&multifd->load_bufs_buffer_ready_cond, >> +                           &multifd->load_bufs_mutex); >> +            continue; >> +        } >> + >> +        if (multifd->load_buf_idx == multifd->load_buf_idx_last) { >> +            break; >> +        } >> + >> +        if (multifd->load_buf_idx == 0) { >> +            trace_vfio_load_state_device_buffer_start(vbasedev->name); >> +        } >> + >> +        if (!vfio_load_state_buffer_write(vbasedev, lb, errp)) { >> +            ret = false; >> +            goto ret_signal; >> +        } >> + >> +        assert(multifd->load_buf_queued_pending_buffers > 0); >> +        multifd->load_buf_queued_pending_buffers--; >> + >> +        if (multifd->load_buf_idx == multifd->load_buf_idx_last - 1) { >> +            trace_vfio_load_state_device_buffer_end(vbasedev->name); >> +        } >> + >> +        multifd->load_buf_idx++; >> +    } >> + >> +    if (vfio_load_bufs_thread_want_abort(multifd, should_quit)) { >> +        error_setg(errp, "operation cancelled"); >> +        ret = false; >> +        goto ret_signal; >> +    } >> + >> +    if (vfio_load_config_after_iter(vbasedev)) { >> +        while (!multifd->load_bufs_iter_done) { >> +            qemu_cond_wait(&multifd->load_bufs_iter_done_cond, >> +                           &multifd->load_bufs_mutex); >> + >> +            if (vfio_load_bufs_thread_want_abort(multifd, should_quit)) { >> +                error_setg(errp, "operation cancelled"); >> +                ret = false; >> +                goto ret_signal; >> +            } >> +        } >> +    } > > Please put the above chunck at the end of the series with the patch > adding ARM support. I think load_bufs_iter_done_cond should be moved > out of this patch too. > > > > Thanks, > > C. > > > >> +    config_ret = vfio_load_bufs_thread_load_config(vbasedev); >> +    if (config_ret) { >> +        error_setg(errp, "load config state failed: %d", config_ret); >> +        ret = false; >> +    } >> + >> +ret_signal: >> +    multifd->load_bufs_thread_running = false; >> +    qemu_cond_signal(&multifd->load_bufs_thread_finished_cond); >> + >> +    return ret; >> +} >> + >>   static int vfio_save_device_config_state(QEMUFile *f, void *opaque, >>                                            Error **errp) >>   { >> @@ -517,11 +690,40 @@ static VFIOMultifd *vfio_multifd_new(void) >>       multifd->load_buf_queued_pending_buffers = 0; >>       qemu_cond_init(&multifd->load_bufs_buffer_ready_cond); >> +    multifd->load_bufs_iter_done = false; >> +    qemu_cond_init(&multifd->load_bufs_iter_done_cond); >> + >> +    multifd->load_bufs_thread_running = false; >> +    multifd->load_bufs_thread_want_exit = false; >> +    qemu_cond_init(&multifd->load_bufs_thread_finished_cond); >> + >>       return multifd; >>   } >> +static void vfio_load_cleanup_load_bufs_thread(VFIOMultifd *multifd) >> +{ >> +    /* The lock order is load_bufs_mutex -> BQL so unlock BQL here first */ >> +    bql_unlock(); >> +    WITH_QEMU_LOCK_GUARD(&multifd->load_bufs_mutex) { >> +        while (multifd->load_bufs_thread_running) { >> +            multifd->load_bufs_thread_want_exit = true; >> + >> +            qemu_cond_signal(&multifd->load_bufs_buffer_ready_cond); >> +            qemu_cond_signal(&multifd->load_bufs_iter_done_cond); >> +            qemu_cond_wait(&multifd->load_bufs_thread_finished_cond, >> +                           &multifd->load_bufs_mutex); >> +        } >> +    } >> +    bql_lock(); >> +} >> + >>   static void vfio_multifd_free(VFIOMultifd *multifd) >>   { >> +    vfio_load_cleanup_load_bufs_thread(multifd); >> + >> +    qemu_cond_destroy(&multifd->load_bufs_thread_finished_cond); >> +    qemu_cond_destroy(&multifd->load_bufs_iter_done_cond); >> +    vfio_state_buffers_destroy(&multifd->load_bufs); >>       qemu_cond_destroy(&multifd->load_bufs_buffer_ready_cond); >>       qemu_mutex_destroy(&multifd->load_bufs_mutex); >> @@ -1042,6 +1244,32 @@ static bool vfio_switchover_ack_needed(void *opaque) >>       return vfio_precopy_supported(vbasedev); >>   } >> +static int vfio_switchover_start(void *opaque) >> +{ >> +    VFIODevice *vbasedev = opaque; >> +    VFIOMigration *migration = vbasedev->migration; >> +    VFIOMultifd *multifd = migration->multifd; >> + >> +    if (!migration->multifd_transfer) { >> +        /* Load thread is only used for multifd transfer */ >> +        return 0; >> +    } >> + >> +    assert(multifd); >> + >> +    /* The lock order is load_bufs_mutex -> BQL so unlock BQL here first */ >> +    bql_unlock(); >> +    WITH_QEMU_LOCK_GUARD(&multifd->load_bufs_mutex) { >> +        assert(!multifd->load_bufs_thread_running); >> +        multifd->load_bufs_thread_running = true; >> +    } >> +    bql_lock(); >> + >> +    qemu_loadvm_start_load_thread(vfio_load_bufs_thread, vbasedev); and please move these changes under a vfio_multifd_switchover_start() routine. Thanks, C. >> +    return 0; >> +} >> + >>   static const SaveVMHandlers savevm_vfio_handlers = { >>       .save_prepare = vfio_save_prepare, >>       .save_setup = vfio_save_setup, >> @@ -1057,6 +1285,7 @@ static const SaveVMHandlers savevm_vfio_handlers = { >>       .load_state = vfio_load_state, >>       .load_state_buffer = vfio_load_state_buffer, >>       .switchover_ack_needed = vfio_switchover_ack_needed, >> +    .switchover_start = vfio_switchover_start, >>   }; >>   /* ---------------------------------------------------------------------- */ >> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events >> index 042a3dc54a33..418b378ebd29 100644 >> --- a/hw/vfio/trace-events >> +++ b/hw/vfio/trace-events >> @@ -154,6 +154,11 @@ vfio_load_device_config_state_end(const char *name) " (%s)" >>   vfio_load_state(const char *name, uint64_t data) " (%s) data 0x%"PRIx64 >>   vfio_load_state_device_data(const char *name, uint64_t data_size, int ret) " (%s) size %"PRIu64" ret %d" >>   vfio_load_state_device_buffer_incoming(const char *name, uint32_t idx) " (%s) idx %"PRIu32 >> +vfio_load_state_device_buffer_start(const char *name) " (%s)" >> +vfio_load_state_device_buffer_starved(const char *name, uint32_t idx) " (%s) idx %"PRIu32 >> +vfio_load_state_device_buffer_load_start(const char *name, uint32_t idx) " (%s) idx %"PRIu32 >> +vfio_load_state_device_buffer_load_end(const char *name, uint32_t idx) " (%s) idx %"PRIu32 >> +vfio_load_state_device_buffer_end(const char *name) " (%s)" >>   vfio_migration_realize(const char *name) " (%s)" >>   vfio_migration_set_device_state(const char *name, const char *state) " (%s) state %s" >>   vfio_migration_set_state(const char *name, const char *new_state, const char *recover_state) " (%s) new state %s, recover state %s" >> >