{"id":2227794,"url":"http://patchwork.ozlabs.org/api/1.1/patches/2227794/?format=json","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=json","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=json","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=json","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":"","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 ; 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 )\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 )\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 )\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 ","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 ","Cc":"Paolo Bonzini ,\n \"Michael S. Tsirkin\" ,\n =?utf-8?q?Alex_Benn=C3=A9e?= ,\n Akihiko Odaki ","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 ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","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 \nTested-by: Dmitry Osipenko \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"]}