From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj2-f12.google.com (mail-pj2-f12.google.com [74.125.227.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 79BFC37EFF1 for ; Sun, 27 Sep 2026 04:09:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.227.140 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790482159; cv=none; b=PK8Zz3Fvxx+9OnorpjY925sN3ftjhhMqHgnDi6BHxLGK/A8mVhd2GwytGZIKoGHQXgFbrts/5gwnvKZyxUFUZwrR0GEnDDIQsfPufatEo81jvYVL4B0tYwavUt3zrNOJsGrayuHGtxlMmYjFHH7f+wtLOCDlehH++1IAHoWMLOc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790482159; c=relaxed/simple; bh=2LjSmy5wQ+RbKF7JAhK6ovvEPU2UEhSF5hUQSR7JJEs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ef6nimiocZnw0ngnOv7G1ya+Kb08G0HqeyurSpuieGLiotEkqIJJ72CDRpfudJ/bgG4e8e6o7n0Jytp2giu+pk9Htt4TB7/5BcB8hCiV8KaZlEnC8QXrrDdl5GEcYfK5TRJ491iYWhZrALN/KDGMU2XzwhUXpWW8mKLaaEWV1Zw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=IOprq73l; arc=none smtp.client-ip=74.125.227.140 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="IOprq73l" Received: by mail-pj2-f12.google.com with SMTP id 98e67ed59e1d1-398b3b189e0so1084359a91.2 for ; Sat, 26 Sep 2026 21:09:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1790482158; x=1791086958; darn=lists.linux.dev; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=2LjSmy5wQ+RbKF7JAhK6ovvEPU2UEhSF5hUQSR7JJEs=; b=IOprq73ljazuiiFNIT8rjTX4gTtDdSXs5H6eB+Do9X4DWz9/Cvx3ZtQ50Rq1iA/LEs sb2dU2PPx8DXIS9DDSsvh1R5f1l0/lXeAD7yfBCX1zeecFccNGCFjYIz/PN9N925lK5I 7gIvX8nS6xLQA04rlOxvZi1zzsfLIvndgmbq3/jLoSvFu5bUlJTRGyPaZd1/jlZUBVup jZRC9OBxk2FZXbcJ8Ts+z+Owp7AStVJ7bfKf9BxT6VsBccfoZfkPWeuj+SHJpc9iE72Z UHchh6rLpRcOxb7D4sZKg4Q1aYIR05n0csNd8uG+R1bn1hkDlSovsiFJRrOTRD6VF04S Ls4A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790482158; x=1791086958; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=2LjSmy5wQ+RbKF7JAhK6ovvEPU2UEhSF5hUQSR7JJEs=; b=DduSCS9P250kZEgbAjXdzhhASmhATp6vVUvsPXeegIls4M8ergIJJL11xY8ykze18h QJRPLy5COo7AqK8rnFJAYnAJH66dGO5+yFQCEBdp7lSMV4OQsc/iYYDYEciRTP41VwLY 40mcwaJAyf0Ex5HZFn07pDKtCHmyeqtmD0lmlN0J1F4H7Bjf9RDglMdacSE1QxQOCriB TVbxG2wMQmBbGIv94+7tbi+uY0pWYTN8RyoJ+FtWQzeQ+KfT5SRuOYUK3IoPeajP5VYl 4Oh+ntIrjPP2y4JhkMPYJ5nVNoEN6flzTd7Pqy8oyhMiFHxx36h8SghiDPx46oj1Vh36 6VeA== X-Forwarded-Encrypted: i=1; AKwUvBwjEIlfAsGg+YdvksEG9fS1YdPxWxMjH+MRlvdBXlIH+gGP7Ufbbf2J0VRQ4t9thHdhc+cC0vF/1knf0C0fbw==@lists.linux.dev X-Gm-Message-State: AFq9FYIRFFc+rQ/+3FbA0jL3Eyd9uk/g5ChqmSNGXKBga3WY8KLSRJoK VF6kHEyfEzNzsHO/HHpUclFKcx0nFIAMZULDe46THfN8o36a70r7dkze X-Gm-Gg: AYBFou3UpQe6sdr03bSSkqG2bqTgY8jWzaV2YRsndBqsd4P0oD6cVcwPnkX2cprgJ4p jTuid4wrYoPrwugOKpZSlWCs5RJ1myZJeE7Nlv0eZKrIwomU4t+Ss3UQB6UHrYCYvW/fHVfB1xM ICGw19UTl/WDKekhD+G0DyB33htlgajkEbugALMy0I1qqA1wWjnxgel9PTIxaCWsvH0y07C9yb+ ADOn6lq+37hLy+tp4kK1E6uwGgxSMiyUfq383vwy9vkJ0s038GjwzhQ5mqQDxVPQY7/JVseN/ol 9VJtoeSnejt3RsLyY+M173a016WrlMGLTxxohlSvFbEORmy9Ys8PsI2kz+mwfOaLC3kwJeJt79C 6IfW9SqvfAdNtkqxWQ+1P1Q5GJX20uifjuC7FwY1YxBGXEfic0m+4RwothFShsPTPxWLXvIIouv elx3HUFBKX2VVGv+Eb6HcXkE29yRbQoszuc6yguNG1lr6NfF0XlHMQVxolZvwfUIbMQBFM5iviz 7mnnp253fsfXxRr X-Received: by 2002:a17:90b:5107:b0:3a0:d823:c750 with SMTP id 98e67ed59e1d1-3a0d823cb37mr3049456a91.49.1790482157721; Sat, 26 Sep 2026 21:09:17 -0700 (PDT) Received: from thangnn-ASUS.. ([2405:4802:1d4a:e90:3a0c:2ea9:4ab7:bd1b]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3a09766210bsm18717708a91.8.2026.09.26.21.09.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 26 Sep 2026 21:09:17 -0700 (PDT) From: Nguyen Ngoc Thang To: Hillf Danton Cc: David Airlie , Gerd Hoffmann , Dmitry Osipenko , Gurchetan Singh , Thomas Zimmermann , linux-kernel@vger.kernel.org, syzbot+1b129b44597a126d2d79@syzkaller.appspotmail.com, dri-devel@lists.freedesktop.org, virtualization@lists.linux.dev Subject: Re: [PATCH] drm/virtio: share one vbuf cache across all devices Date: Sun, 27 Sep 2026 11:09:11 +0700 Message-ID: <20260927040911.15181-1-ngocthang2710.1999@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260927000323.299-1-hdanton@sina.com> References: <20260927000323.299-1-hdanton@sina.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Sun, 27 Sep 2026, Hillf Danton wrote: > What is unclear -- why is kmalloc failing to work in 2026? kmalloc isn't failing. The failure is in kmem_cache_create(): the driver creates a dedicated cache with a fixed global name for each device, so a second probe while the first drm_device is still alive (release is deferred by an open /dev/fbN) trips the duplicate-name check. Your question made me look at whether the dedicated cache is needed at all. A vbuf is sizeof(struct virtio_gpu_vbuffer) + 96 + 24 = 216 bytes, which lands in kmalloc-256 anyway, so the cache buys nothing over kzalloc()/kfree(). Dropping it also removes the lifetime problem entirely and needs no module-level state. I'll send a v2 that switches the kmem_cache_zalloc() calls and kmem_cache_free() to kzalloc()/kfree() and deletes the cache setup and teardown. Thanks, Nguyen Ngoc Thang