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GET /api/patches/2218155/?format=api
{ "id": 2218155, "url": "http://patchwork.ozlabs.org/api/patches/2218155/?format=api", "web_url": "http://patchwork.ozlabs.org/project/qemu-devel/patch/20260331134721.96047-1-maxpain@linux.com/", "project": { "id": 14, "url": "http://patchwork.ozlabs.org/api/projects/14/?format=api", "name": "QEMU Development", "link_name": "qemu-devel", "list_id": "qemu-devel.nongnu.org", "list_email": "qemu-devel@nongnu.org", "web_url": "", "scm_url": "", "webscm_url": "", "list_archive_url": "", "list_archive_url_format": "", "commit_url_format": "" }, "msgid": "<20260331134721.96047-1-maxpain@linux.com>", "list_archive_url": null, "date": "2026-03-31T13:47:21", "name": "[v2] vhost-user-blk: do not force VIRTIO_BLK_F_SIZE_MAX", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "73ef278394afdd36f245c9451ace9a45e55786ac", "submitter": { "id": 93011, "url": "http://patchwork.ozlabs.org/api/people/93011/?format=api", "name": "Max Makarov", "email": "maxpain177@gmail.com" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/qemu-devel/patch/20260331134721.96047-1-maxpain@linux.com/mbox/", "series": [ { "id": 498202, "url": "http://patchwork.ozlabs.org/api/series/498202/?format=api", "web_url": "http://patchwork.ozlabs.org/project/qemu-devel/list/?series=498202", "date": "2026-03-31T13:47:21", "name": "[v2] vhost-user-blk: do not force VIRTIO_BLK_F_SIZE_MAX", "version": 2, "mbox": "http://patchwork.ozlabs.org/series/498202/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2218155/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2218155/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "<qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org>", "X-Original-To": "incoming@patchwork.ozlabs.org", "Delivered-To": "patchwork-incoming@legolas.ozlabs.org", "Authentication-Results": [ "legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20251104 header.b=FZBK1OfL;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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Tsirkin\" <mst@redhat.com>, Kevin Wolf <kwolf@redhat.com>,\n Hanna Reitz <hreitz@redhat.com>, Max Makarov <maxpain@linux.com>", "Subject": "[PATCH v2] vhost-user-blk: do not force VIRTIO_BLK_F_SIZE_MAX", "Date": "Tue, 31 Mar 2026 16:47:21 +0300", "Message-ID": "<20260331134721.96047-1-maxpain@linux.com>", "X-Mailer": "git-send-email 2.50.1", "MIME-Version": "1.0", "Content-Transfer-Encoding": "8bit", "Received-SPF": "pass client-ip=2a00:1450:4864:20::12f;\n envelope-from=maxpain177@gmail.com; helo=mail-lf1-x12f.google.com", "X-Spam_score_int": "-17", "X-Spam_score": "-1.8", "X-Spam_bar": "-", "X-Spam_report": "(-1.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1,\n DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1,\n FREEMAIL_ENVFROM_END_DIGIT=0.25, FREEMAIL_FROM=0.001,\n RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001,\n 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": "qemu development <qemu-devel.nongnu.org>", "List-Unsubscribe": "<https://lists.nongnu.org/mailman/options/qemu-devel>,\n <mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>", "List-Archive": "<https://lists.nongnu.org/archive/html/qemu-devel>", "List-Post": "<mailto:qemu-devel@nongnu.org>", "List-Help": "<mailto:qemu-devel-request@nongnu.org?subject=help>", "List-Subscribe": "<https://lists.nongnu.org/mailman/listinfo/qemu-devel>,\n <mailto:qemu-devel-request@nongnu.org?subject=subscribe>", "Errors-To": "qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org", "Sender": "qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org" }, "content": "vhost_user_blk_get_features() unconditionally advertises\nVIRTIO_BLK_F_SIZE_MAX regardless of what the backend reports in\nits config. The built-in QSD vhost-user-blk backend sets\nsize_max=0, creating a contradictory state where the feature bit\ntells the guest that size_max is valid but the value is zero.\n\nThe in-process virtio-blk device does not advertise\nVIRTIO_BLK_F_SIZE_MAX (it also sets size_max=0 in config), so\nguests never see this contradiction with native virtio-blk.\n\nLinux tolerates size_max=0 because blk_validate_limits() silently\ncorrects max_segment_size=0 to BLK_MAX_SEGMENT_SIZE (65536).\nWindows viostor, however, trusts the feature bit and uses the raw\nsize_max=0 in its scatter-gather calculations, producing\nzero-length segments that hang I/O. The disk appears empty to\nWindows (no GPT, no partitions), causing INACCESSIBLE_BOOT_DEVICE.\n\nStop force-adding VIRTIO_BLK_F_SIZE_MAX in the frontend. The\nfeature remains in user_feature_bits[], so backends that properly\nadvertise it with a valid config value will still work.\n\nSigned-off-by: Max Makarov <maxpain@linux.com>\n---\nv2:\n - Remove the VIRTIO_BLK_F_SIZE_MAX feature bit from the frontend\n instead of setting size_max=4096 in the backend config [Kevin Wolf]\n - Fix incorrect claim about Linux PAGE_SIZE fallback\n - Drop unrelated Buglink tags\n---\n hw/block/vhost-user-blk.c | 1 -\n 1 file changed, 1 deletion(-)", "diff": "diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c\nindex c151e83..7ba6562 100644\n--- a/hw/block/vhost-user-blk.c\n+++ b/hw/block/vhost-user-blk.c\n@@ -273,7 +273,6 @@ static uint64_t vhost_user_blk_get_features(VirtIODevice *vdev,\n VHostUserBlk *s = VHOST_USER_BLK(vdev);\n \n /* Turn on pre-defined features */\n- virtio_add_feature(&features, VIRTIO_BLK_F_SIZE_MAX);\n virtio_add_feature(&features, VIRTIO_BLK_F_SEG_MAX);\n virtio_add_feature(&features, VIRTIO_BLK_F_GEOMETRY);\n virtio_add_feature(&features, VIRTIO_BLK_F_TOPOLOGY);\n", "prefixes": [ "v2" ] }