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([2a01:cb19:9004:d500:a732:5611:7f59:8bb3]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-390e4795d30sm1048245f8f.10.2025.02.26.22.48.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 26 Feb 2025 22:48:41 -0800 (PST) Message-ID: <11ecf7fb-55f6-4606-b635-e53dbcc71dbc@redhat.com> Date: Thu, 27 Feb 2025 07:48:39 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 34/36] vfio/migration: Max in-flight VFIO device state buffer count limit 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: <719b309bb7bc13542d14e6ce0026cb9bb67e9f31.1739994627.git.maciej.szmigiero@oracle.com> 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: <719b309bb7bc13542d14e6ce0026cb9bb67e9f31.1739994627.git.maciej.szmigiero@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit 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: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.44, 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 2/19/25 21:34, Maciej S. Szmigiero wrote: > From: "Maciej S. Szmigiero" > > Allow capping the maximum count of in-flight VFIO device state buffers > queued at the destination, otherwise a malicious QEMU source could > theoretically cause the target QEMU to allocate unlimited amounts of memory > for buffers-in-flight. > > Since this is not expected to be a realistic threat in most of VFIO live > migration use cases and the right value depends on the particular setup > disable the limit by default by setting it to UINT64_MAX. > > Signed-off-by: Maciej S. Szmigiero > --- > hw/vfio/migration-multifd.c | 14 ++++++++++++++ > hw/vfio/pci.c | 2 ++ > include/hw/vfio/vfio-common.h | 1 + > 3 files changed, 17 insertions(+) > > diff --git a/hw/vfio/migration-multifd.c b/hw/vfio/migration-multifd.c > index 18a5ff964a37..04aa3f4a6596 100644 > --- a/hw/vfio/migration-multifd.c > +++ b/hw/vfio/migration-multifd.c > @@ -53,6 +53,7 @@ typedef struct VFIOMultifd { > QemuMutex load_bufs_mutex; /* Lock order: this lock -> BQL */ > uint32_t load_buf_idx; > uint32_t load_buf_idx_last; > + uint32_t load_buf_queued_pending_buffers; > } VFIOMultifd; > > static void vfio_state_buffer_clear(gpointer data) > @@ -121,6 +122,15 @@ static bool vfio_load_state_buffer_insert(VFIODevice *vbasedev, > > assert(packet->idx >= multifd->load_buf_idx); > > + multifd->load_buf_queued_pending_buffers++; > + if (multifd->load_buf_queued_pending_buffers > > + vbasedev->migration_max_queued_buffers) { > + error_setg(errp, > + "queuing state buffer %" PRIu32 " would exceed the max of %" PRIu64, > + packet->idx, vbasedev->migration_max_queued_buffers); > + return false; > + } > + > lb->data = g_memdup2(&packet->data, packet_total_size - sizeof(*packet)); > lb->len = packet_total_size - sizeof(*packet); > lb->is_present = true; > @@ -374,6 +384,9 @@ static bool vfio_load_bufs_thread(void *opaque, bool *should_quit, Error **errp) > 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); > } > @@ -408,6 +421,7 @@ VFIOMultifd *vfio_multifd_new(void) > > multifd->load_buf_idx = 0; > multifd->load_buf_idx_last = UINT32_MAX; > + multifd->load_buf_queued_pending_buffers = 0; > qemu_cond_init(&multifd->load_bufs_buffer_ready_cond); > > multifd->load_bufs_thread_running = false; > diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c > index 9111805ae06c..247418f0fce2 100644 > --- a/hw/vfio/pci.c > +++ b/hw/vfio/pci.c > @@ -3383,6 +3383,8 @@ static const Property vfio_pci_dev_properties[] = { > vbasedev.migration_multifd_transfer, > qdev_prop_on_off_auto_mutable, OnOffAuto, > .set_default = true, .defval.i = ON_OFF_AUTO_AUTO), > + DEFINE_PROP_UINT64("x-migration-max-queued-buffers", VFIOPCIDevice, > + vbasedev.migration_max_queued_buffers, UINT64_MAX), UINT64_MAX doesn't make sense to me. What would be a reasonable value ? Have you monitored the max ? Should we collect some statistics on this value and raise a warning if a high water mark is reached ? I think this would more useful. > DEFINE_PROP_BOOL("migration-events", VFIOPCIDevice, > vbasedev.migration_events, false), > DEFINE_PROP_BOOL("x-no-mmap", VFIOPCIDevice, vbasedev.no_mmap, false), Please add property documentation in vfio_pci_dev_class_init() Thanks, C. > diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h > index 3006931accf6..30a5bb9af61b 100644 > --- a/include/hw/vfio/vfio-common.h > +++ b/include/hw/vfio/vfio-common.h > @@ -155,6 +155,7 @@ typedef struct VFIODevice { > bool ram_block_discard_allowed; > OnOffAuto enable_migration; > OnOffAuto migration_multifd_transfer; > + uint64_t migration_max_queued_buffers; > bool migration_events; > VFIODeviceOps *ops; > unsigned int num_irqs; >