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GET /api/patches/2218201/?format=api
{ "id": 2218201, "url": "http://patchwork.ozlabs.org/api/patches/2218201/?format=api", "web_url": "http://patchwork.ozlabs.org/project/qemu-devel/patch/20260331152856.1802-1-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": "<20260331152856.1802-1-maxpain@linux.com>", "list_archive_url": null, "date": "2026-03-31T15:28:56", "name": "vhost-user-blk-server: do not advertise VIRTIO_BLK_F_SIZE_MAX with size_max=0", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "e6f8e12d3c936b917c4d6f4345ede62b1cd101d6", "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/20260331152856.1802-1-maxpain@linux.com/mbox/", "series": [ { "id": 498224, "url": "http://patchwork.ozlabs.org/api/series/498224/?format=api", "web_url": "http://patchwork.ozlabs.org/project/qemu-devel/list/?series=498224", "date": "2026-03-31T15:28:56", "name": "vhost-user-blk-server: do not advertise VIRTIO_BLK_F_SIZE_MAX with size_max=0", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/498224/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2218201/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2218201/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=NsW0YTzs;\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] vhost-user-blk-server: do not advertise VIRTIO_BLK_F_SIZE_MAX\n with size_max=0", "Date": "Tue, 31 Mar 2026 18:28:56 +0300", "Message-ID": "<20260331152856.1802-1-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::12c;\n envelope-from=maxpain177@gmail.com; helo=mail-lf1-x12c.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=unavailable 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": "The QSD vhost-user-blk backend advertises VIRTIO_BLK_F_SIZE_MAX but\nsets size_max=0 in config, creating a contradictory state. The feature\nbit tells the guest that size_max is valid, but the value is zero.\n\nWindows viostor trusts the feature bit, reads size_max=0, and uses it\nin scatter-gather calculations producing zero-length segments that hang\nI/O. The disk appears empty (no GPT, no partitions), causing\nINACCESSIBLE_BOOT_DEVICE BSOD. Linux tolerates this because\nblk_validate_limits() silently corrects max_segment_size=0 to\nBLK_MAX_SEGMENT_SIZE (65536).\n\nThis affects any VMM using QSD as a vhost-user-blk backend (QEMU,\nCloud Hypervisor, etc.), since both pass through SIZE_MAX from the\nbackend to the guest via feature intersection.\n\nRemove VIRTIO_BLK_F_SIZE_MAX from the backend feature bits. The\nsize_max config field remains zero but is now ignored by guests since\nthe feature is not negotiated.\n\nSigned-off-by: Max Makarov <maxpain@linux.com>\n---\n block/export/vhost-user-blk-server.c | 2 +-\n 1 file changed, 1 insertion(+), 1 deletion(-)", "diff": "diff --git a/block/export/vhost-user-blk-server.c b/block/export/vhost-user-blk-server.c\nindex e89422b..b6b03b0 100644\n--- a/block/export/vhost-user-blk-server.c\n+++ b/block/export/vhost-user-blk-server.c\n@@ -119,7 +119,7 @@ static uint64_t vu_blk_get_features(VuDev *dev)\n uint64_t features;\n VuServer *server = container_of(dev, VuServer, vu_dev);\n VuBlkExport *vexp = container_of(server, VuBlkExport, vu_server);\n- features = 1ull << VIRTIO_BLK_F_SIZE_MAX |\n+ features =\n 1ull << VIRTIO_BLK_F_SEG_MAX |\n 1ull << VIRTIO_BLK_F_TOPOLOGY |\n 1ull << VIRTIO_BLK_F_BLK_SIZE |\n", "prefixes": [] }