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GET /api/1.1/patches/2227794/?format=api
{ "id": 2227794, "url": "http://patchwork.ozlabs.org/api/1.1/patches/2227794/?format=api", "web_url": "http://patchwork.ozlabs.org/project/qemu-devel/patch/20260424-force_rcu-v4-5-feccfaca0568@rsg.ci.i.u-tokyo.ac.jp/", "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": "<20260424-force_rcu-v4-5-feccfaca0568@rsg.ci.i.u-tokyo.ac.jp>", "date": "2026-04-24T09:27:10", "name": "[v4,5/6] virtio-gpu: Force RCU when unmapping blob", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "3a73ed9e2352e09f874cc1c954757d847d7bf4fa", "submitter": { "id": 90980, "url": "http://patchwork.ozlabs.org/api/1.1/people/90980/?format=api", "name": "Akihiko Odaki", "email": "odaki@rsg.ci.i.u-tokyo.ac.jp" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/qemu-devel/patch/20260424-force_rcu-v4-5-feccfaca0568@rsg.ci.i.u-tokyo.ac.jp/mbox/", "series": [ { "id": 501326, "url": "http://patchwork.ozlabs.org/api/1.1/series/501326/?format=api", "web_url": "http://patchwork.ozlabs.org/project/qemu-devel/list/?series=501326", "date": "2026-04-24T09:27:07", "name": "virtio-gpu: Force RCU when unmapping blob", "version": 4, "mbox": "http://patchwork.ozlabs.org/series/501326/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2227794/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2227794/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=fail reason=\"key not found in DNS\" header.d=rsg.ci.i.u-tokyo.ac.jp\n header.i=@rsg.ci.i.u-tokyo.ac.jp header.a=rsa-sha256 header.s=rs20250326\n header.b=PkJdCx71;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; helo=lists1p.gnu.org;\n envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org;\n receiver=patchwork.ozlabs.org)" ], "Received": [ "from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17])\n\t(using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits))\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4g271p2n7Bz1xvV\n\tfor <incoming@patchwork.ozlabs.org>; Fri, 24 Apr 2026 19:28:46 +1000 (AEST)", "from localhost ([::1] helo=lists1p.gnu.org)\n\tby lists1p.gnu.org with esmtp (Exim 4.90_1)\n\t(envelope-from <qemu-devel-bounces@nongnu.org>)\n\tid 1wGCpX-00082u-H1; Fri, 24 Apr 2026 05:28:11 -0400", "from eggs.gnu.org ([2001:470:142:3::10])\n by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)\n (Exim 4.90_1) (envelope-from <odaki@rsg.ci.i.u-tokyo.ac.jp>)\n id 1wGCp4-0007P0-DC\n for qemu-devel@nongnu.org; Fri, 24 Apr 2026 05:27:42 -0400", "from www3579.sakura.ne.jp ([49.212.243.89])\n by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)\n (Exim 4.90_1) (envelope-from <odaki@rsg.ci.i.u-tokyo.ac.jp>)\n id 1wGCoz-0007a8-Sm\n for qemu-devel@nongnu.org; Fri, 24 Apr 2026 05:27:42 -0400", "from h205.csg.ci.i.u-tokyo.ac.jp (h205.csg.ci.i.u-tokyo.ac.jp\n [133.11.54.205]) (authenticated bits=0)\n by www3579.sakura.ne.jp (8.16.1/8.16.1) with ESMTPSA id 63O9RHIh004358\n (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO);\n Fri, 24 Apr 2026 18:27:27 +0900 (JST)\n (envelope-from odaki@rsg.ci.i.u-tokyo.ac.jp)" ], "DKIM-Signature": "a=rsa-sha256; bh=nzLYRcuCdqFWfvHtoSoGlURTO6nugE9Dg725YsMRZMk=;\n c=relaxed/relaxed; d=rsg.ci.i.u-tokyo.ac.jp;\n h=From:Message-Id:To:Subject:Date;\n s=rs20250326; t=1777022847; v=1;\n b=PkJdCx71mqP5xdztHYREDyrpAusenbp+oGE71U1ts5EaNWo7kMptSlOrHwB0EJ7t\n YipfuNjOF33OqPuGIGW8+CXBEfjBJcEH7W3ZstWQscHfczxvLkMzQZItuW2qmeyI\n EjfRgzTMEPurkrJeOiF5ZVguwR2zbeFtxIeksDskMrzhZl3zoP7sHAPnNsTSzhx0\n VrktpSi1/YJuwNKTaN+D3NO7MxtifyvrFCwD3eamYYCN2zLzDq6w5xBs2/M023N4\n eOpQvNkwJyho/Z7mT27eEE68vIpZjc1mdfsq0mXSZoiJLS1xYsb/DRomnnwP2zdN\n hyuA8RJnhKR0i16KAYi9qQ==", "From": "Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>", "Date": "Fri, 24 Apr 2026 18:27:10 +0900", "Subject": "[PATCH v4 5/6] virtio-gpu: Force RCU when unmapping blob", "MIME-Version": "1.0", "Content-Type": "text/plain; charset=\"utf-8\"", "Content-Transfer-Encoding": "7bit", "Message-Id": "<20260424-force_rcu-v4-5-feccfaca0568@rsg.ci.i.u-tokyo.ac.jp>", "References": "<20260424-force_rcu-v4-0-feccfaca0568@rsg.ci.i.u-tokyo.ac.jp>", "In-Reply-To": "<20260424-force_rcu-v4-0-feccfaca0568@rsg.ci.i.u-tokyo.ac.jp>", "To": "qemu-devel@nongnu.org, Dmitry Osipenko <dmitry.osipenko@collabora.com>", "Cc": "Paolo Bonzini <pbonzini@redhat.com>,\n \"Michael S. Tsirkin\" <mst@redhat.com>,\n =?utf-8?q?Alex_Benn=C3=A9e?= <alex.bennee@linaro.org>,\n Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>", "X-Mailer": "b4 0.16-dev-16047", "Received-SPF": "pass client-ip=49.212.243.89;\n envelope-from=odaki@rsg.ci.i.u-tokyo.ac.jp; helo=www3579.sakura.ne.jp", "X-Spam_score_int": "-16", "X-Spam_score": "-1.7", "X-Spam_bar": "-", "X-Spam_report": "(-1.7 / 5.0 requ) BAYES_00=-1.9, DKIM_INVALID=0.1,\n DKIM_SIGNED=0.1, SPF_HELO_NONE=0.001,\n SPF_PASS=-0.001 autolearn=no 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": "Unmapping a blob changes the memory map, which is protected with RCU.\nRCU is designed to minimize the read-side overhead at the cost of\nreclamation delay. While this design usually makes sense, it is\nproblematic when unmapping a blob because the operation blocks all\nvirtio-gpu commands and causes perceivable disruption.\n\nMinimize such the disruption with force_rcu(), which minimizes the\nreclamation delay at the cost of a read-side overhead.\n\nSigned-off-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>\nTested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>\n---\n hw/display/virtio-gpu-virgl.c | 1 +\n 1 file changed, 1 insertion(+)", "diff": "diff --git a/hw/display/virtio-gpu-virgl.c b/hw/display/virtio-gpu-virgl.c\nindex b7a2d160ddd8..69896618fef8 100644\n--- a/hw/display/virtio-gpu-virgl.c\n+++ b/hw/display/virtio-gpu-virgl.c\n@@ -298,6 +298,7 @@ virtio_gpu_virgl_unmap_resource_blob(VirtIOGPU *g,\n /* memory region owns self res->mr object and frees it by itself */\n memory_region_del_subregion(&b->hostmem, mr);\n object_unparent(OBJECT(vmr));\n+ force_rcu();\n \n /* Fallthrough */\n case VIRTIO_GPU_MR_UNMAP_STARTED:\n", "prefixes": [ "v4", "5/6" ] }