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GET /api/1.1/patches/2225847/?format=api
{ "id": 2225847, "url": "http://patchwork.ozlabs.org/api/1.1/patches/2225847/?format=api", "web_url": "http://patchwork.ozlabs.org/project/qemu-devel/patch/20260421163438.3447280-15-clg@redhat.com/", "project": { "id": 14, "url": "http://patchwork.ozlabs.org/api/1.1/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": "" }, "msgid": "<20260421163438.3447280-15-clg@redhat.com>", "date": "2026-04-21T16:34:38", "name": "[PULL,14/14] vfio-user: fix DMA write reply", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "e1bde85269edd32d2abc70a61bdf9aa9942e5059", "submitter": { "id": 85406, "url": "http://patchwork.ozlabs.org/api/1.1/people/85406/?format=api", "name": "Cédric Le Goater", "email": "clg@redhat.com" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/qemu-devel/patch/20260421163438.3447280-15-clg@redhat.com/mbox/", "series": [ { "id": 500853, "url": "http://patchwork.ozlabs.org/api/1.1/series/500853/?format=api", "web_url": "http://patchwork.ozlabs.org/project/qemu-devel/list/?series=500853", "date": "2026-04-21T16:34:24", "name": "[PULL,01/14] hw/vfio/listener.c: remove CONFIG_KVM", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/500853/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2225847/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2225847/checks/", "tags": {}, "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 (1024-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=fncuQVJR;\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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a=rsa-sha256; c=relaxed/relaxed; d=redhat.com;\n s=mimecast20190719; t=1776789317;\n h=from:from:reply-to:subject:subject:date:date:message-id:message-id:\n to:to:cc:cc:mime-version:mime-version:content-type:content-type:\n content-transfer-encoding:content-transfer-encoding:\n in-reply-to:in-reply-to:references:references;\n bh=L4boacDBWXxI5RCVqYYkYH11QOnnmQygqQshHe9V5xU=;\n b=fncuQVJRDaTBWjn7CDKq7vGkRQXiPqfCCvw+zgJkyv7OKtUY+fQskfv8XwvpWdUZmYfyYL\n wdLUed9mrWOd78oLyLQtCj+XOQj4Fgvq8G2o2HoBARzY5ug75w8bapMBCXSl6HrbXoncTF\n t+qV91WQcSDBRfIXcrnlbZ2BbTxYum0=", "X-MC-Unique": "kl6Dm1SGPSGekxQN19MjgQ-1", "X-Mimecast-MFC-AGG-ID": "kl6Dm1SGPSGekxQN19MjgQ_1776789313", "From": "=?utf-8?q?C=C3=A9dric_Le_Goater?= <clg@redhat.com>", "To": "qemu-devel@nongnu.org", "Cc": "Alex Williamson <alex@shazbot.org>, John Levon <john.levon@nutanix.com>,\n Patrick Mooney <patrick@matx.com>,\n =?utf-8?q?C=C3=A9dric_Le_Goater?= <clg@redhat.com>", "Subject": "[PULL 14/14] vfio-user: fix DMA write reply", "Date": "Tue, 21 Apr 2026 18:34:38 +0200", "Message-ID": "<20260421163438.3447280-15-clg@redhat.com>", "In-Reply-To": "<20260421163438.3447280-1-clg@redhat.com>", "References": "<20260421163438.3447280-1-clg@redhat.com>", "MIME-Version": "1.0", "Content-Type": "text/plain; charset=UTF-8", "Content-Transfer-Encoding": "8bit", "X-Scanned-By": "MIMEDefang 3.0 on 10.30.177.17", "Received-SPF": "pass client-ip=170.10.133.124; envelope-from=clg@redhat.com;\n 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,\n DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1,\n RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_PASS=-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": "From: John Levon <john.levon@nutanix.com>\n\nThe protocol specifies that DMA write replies should include\naddress+count, but the client code was only doing so for read. Fix that\nup.\n\nIn addition, add a protocol clarification over how short writes may be\nreported in that reply. QEMU never reports a short write via the\ncount field.\n\nReported-by: Patrick Mooney <patrick@matx.com>\nSigned-off-by: John Levon <john.levon@nutanix.com>\nReviewed-by: Cédric Le Goater <clg@redhat.com>\nLink: https://lore.kernel.org/qemu-devel/20260410085716.877185-4-john.levon@nutanix.com\nSigned-off-by: Cédric Le Goater <clg@redhat.com>\n---\n docs/interop/vfio-user.rst | 6 ++++++\n hw/vfio-user/pci.c | 30 ++++++++++++++++++++++--------\n 2 files changed, 28 insertions(+), 8 deletions(-)", "diff": "diff --git a/docs/interop/vfio-user.rst b/docs/interop/vfio-user.rst\nindex d4766487ea6d0ee021316890d443814957cf6284..12deb25102af217f7f292b4cb655dc4a6a92439a 100644\n--- a/docs/interop/vfio-user.rst\n+++ b/docs/interop/vfio-user.rst\n@@ -1429,6 +1429,9 @@ Reply\n * *count* is the size of the data transferred.\n * *data* is the data read.\n \n+Note that whether short reads return an error or just set count appropriately is\n+a client-side choice; servers should be prepared to handle both cases.\n+\n ``VFIO_USER_DMA_WRITE``\n -----------------------\n \n@@ -1469,6 +1472,9 @@ Reply\n * *address* is the client DMA memory address being accessed.\n * *count* is the size of the data transferred.\n \n+Note that whether short writes return an error or just set count appropriately\n+is a client-side choice; servers should be prepared to handle both cases.\n+\n ``VFIO_USER_DEVICE_RESET``\n --------------------------\n \ndiff --git a/hw/vfio-user/pci.c b/hw/vfio-user/pci.c\nindex 64b8b3cb8cf5d66879af1703c4f2b5ae0c7418ca..facc79727acb82c35fec5b4bef79e78b3878531a 100644\n--- a/hw/vfio-user/pci.c\n+++ b/hw/vfio-user/pci.c\n@@ -109,6 +109,10 @@ static void vfio_user_dma_read(VFIOPCIDevice *vdev, VFIOUserDMARW *msg)\n \n r = pci_dma_read(pdev, res->offset, &res->data, res->count);\n \n+ /*\n+ * pci_dma_read() doesn't support reporting short reads via the reply's\n+ * count parameter; in this case, we'll reply with an error instead.\n+ */\n switch (r) {\n case MEMTX_OK:\n if (res->hdr.flags & VFIO_USER_NO_REPLY) {\n@@ -136,6 +140,7 @@ static void vfio_user_dma_write(VFIOPCIDevice *vdev, VFIOUserDMARW *msg)\n {\n PCIDevice *pdev = PCI_DEVICE(vdev);\n VFIOUserProxy *proxy = vdev->vbasedev.proxy;\n+ VFIOUserDMARW *res;\n MemTxResult r;\n \n if (msg->hdr.size < sizeof(*msg)) {\n@@ -150,26 +155,35 @@ static void vfio_user_dma_write(VFIOPCIDevice *vdev, VFIOUserDMARW *msg)\n \n r = pci_dma_write(pdev, msg->offset, &msg->data, msg->count);\n \n+ res = g_malloc0(sizeof(*res));\n+ memcpy(res, msg, sizeof(*res));\n+ g_free(msg);\n+\n+ /*\n+ * pci_dma_write() doesn't support reporting short writes via the reply's\n+ * count parameter; in this case, we'll reply with an error instead.\n+ */\n switch (r) {\n case MEMTX_OK:\n- if ((msg->hdr.flags & VFIO_USER_NO_REPLY) == 0) {\n- vfio_user_send_reply(proxy, &msg->hdr, sizeof(msg->hdr));\n- } else {\n- g_free(msg);\n+ if (res->hdr.flags & VFIO_USER_NO_REPLY) {\n+ g_free(res);\n+ return;\n }\n+\n+ vfio_user_send_reply(proxy, &res->hdr, sizeof(*res));\n break;\n case MEMTX_ERROR:\n- vfio_user_send_error(proxy, &msg->hdr, EFAULT);\n+ vfio_user_send_error(proxy, &res->hdr, EFAULT);\n break;\n case MEMTX_DECODE_ERROR:\n- vfio_user_send_error(proxy, &msg->hdr, ENODEV);\n+ vfio_user_send_error(proxy, &res->hdr, ENODEV);\n break;\n case MEMTX_ACCESS_ERROR:\n- vfio_user_send_error(proxy, &msg->hdr, EPERM);\n+ vfio_user_send_error(proxy, &res->hdr, EPERM);\n break;\n default:\n error_printf(\"vfio_user_dma_write unknown error %d\\n\", r);\n- vfio_user_send_error(vdev->vbasedev.proxy, &msg->hdr, EINVAL);\n+ vfio_user_send_error(vdev->vbasedev.proxy, &res->hdr, EINVAL);\n }\n }\n \n", "prefixes": [ "PULL", "14/14" ] }