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([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: linux-kernel@vger.kernel.org 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