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[80.230.32.59]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-430f7475895sm3073017f8f.33.2025.12.13.23.20.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 13 Dec 2025 23:20:40 -0800 (PST) Date: Sun, 14 Dec 2025 02:20:36 -0500 From: "Michael S. Tsirkin" To: Matias Ezequiel Vara Larsen Cc: Francesco Valla , Marc Kleine-Budde , Vincent Mailhol , Harald Mommer , Mikhail Golubev-Ciuchea , Jason Wang , Xuan Zhuo , linux-can@vger.kernel.org, virtualization@lists.linux.dev, Wolfgang Grandegger , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Stefano Garzarella Subject: Re: [PATCH v6] can: virtio: Add virtio CAN driver Message-ID: <20251214022000-mutt-send-email-mst@kernel.org> References: Precedence: bulk X-Mailing-List: linux-can@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Dec 12, 2025 at 04:35:08PM +0100, Matias Ezequiel Vara Larsen wrote: > > > + > > > + priv->can_ctr_msg.cpkt_out.msg_type = cpu_to_le16(msg_type); > > > + sg_init_one(&sg_out, &priv->can_ctr_msg.cpkt_out, > > > + sizeof(priv->can_ctr_msg.cpkt_out)); > > > + sg_init_one(&sg_in, &priv->can_ctr_msg.cpkt_in, sizeof(priv->can_ctr_msg.cpkt_in)); > > > + > > > + err = virtqueue_add_sgs(vq, sgs, 1u, 1u, priv, GFP_ATOMIC); > > > + if (err != 0) { > > > + /* Not expected to happen */ > > > + dev_err(dev, "%s(): virtqueue_add_sgs() failed\n", __func__); > > > + mutex_unlock(&priv->ctrl_lock); > > > + return VIRTIO_CAN_RESULT_NOT_OK; > > > + } > > > + > > > + if (!virtqueue_kick(vq)) { > > > + /* Not expected to happen */ > > > + dev_err(dev, "%s(): Kick failed\n", __func__); > > > + mutex_unlock(&priv->ctrl_lock); > > > + return VIRTIO_CAN_RESULT_NOT_OK; > > > + } > > > + > > > + while (!virtqueue_get_buf(vq, &len) && !virtqueue_is_broken(vq)) > > > + wait_for_completion(&priv->ctrl_done); > > > + > > > > Since the call is synchronous, does can_ctr_msg really need to be part > > of priv? Cannot be it allocated from the stack? > > > > I tried to allocate in the stack but the guest blocks when during `ip > link set up can0`, any idea? you can not DMA to/from the stack, really. -- MST