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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43d7b219576sm4172172f8f.19.2026.04.13.02.18.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Apr 2026 02:18:11 -0700 (PDT) Date: Mon, 13 Apr 2026 10:17:59 +0100 From: David Laight To: "Michael S. Tsirkin" Cc: Jinhui Guo , Jason Wang , Xuan Zhuo , Eugenio =?UTF-8?B?UMOpcmV6?= , Jiri Pirko , virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] virtio_pci_modern: Use GFP_ATOMIC with spin_lock_irqsave held in virtqueue_exec_admin_cmd() Message-ID: <20260413101759.6323fb68@pumpkin> In-Reply-To: <20260413034046-mutt-send-email-mst@kernel.org> References: <20260413072249.30433-1-guojinhui.liam@bytedance.com> <20260413034046-mutt-send-email-mst@kernel.org> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 13 Apr 2026 03:45:20 -0400 "Michael S. Tsirkin" wrote: > On Mon, Apr 13, 2026 at 03:22:49PM +0800, Jinhui Guo wrote: > > virtqueue_exec_admin_cmd() holds admin_vq->lock with spin_lock_irqsave(), > > which disables interrupts. Using GFP_KERNEL inside this critical section > > is unsafe because kmalloc() may sleep, leading to potential deadlocks or > > scheduling violations. > > > > Switch to GFP_ATOMIC to ensure the allocation is non-blocking. > > > > Fixes: 4c3b54af907e ("virtio_pci_modern: use completion instead of busy loop to wait on admin cmd result") > > Cc: stable@vger.kernel.org > > Signed-off-by: Jinhui Guo > > --- > > drivers/virtio/virtio_pci_modern.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c > > index 6d8ae2a6a8ca..db8e4f88b749 100644 > > --- a/drivers/virtio/virtio_pci_modern.c > > +++ b/drivers/virtio/virtio_pci_modern.c > > @@ -101,7 +101,7 @@ static int virtqueue_exec_admin_cmd(struct virtio_pci_admin_vq *admin_vq, > > return -EIO; > > > > spin_lock_irqsave(&admin_vq->lock, flags); > > - ret = virtqueue_add_sgs(vq, sgs, out_num, in_num, cmd, GFP_KERNEL); > > + ret = virtqueue_add_sgs(vq, sgs, out_num, in_num, cmd, GFP_ATOMIC); > > if (ret < 0) { > > if (ret == -ENOSPC) { > > spin_unlock_irqrestore(&admin_vq->lock, flags); > > > GFP_ATOMIC allocations can and will fail. If using them, one must > retry, not just propagate failures. > Or just switch admin_vq->lock to a mutex? Or do the allocate before acquiring the lock (and free it not used in the error path). David > > > > -- > > 2.20.1 > >