From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8AED0268684; Mon, 14 Jul 2025 15:21:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752506491; cv=none; b=oQI9ePMCobPCkv4HlK5eMX06zJFuS4ak0Qzv55ObnMLLxwq/ysq1ZbNa3OMFf824Ya9nLAf4ewv6hbsZdGI9PuJxYWMkputy2EPnqvC5QXdgTbxeJ8UnoS2901im3KDiCySWR4p2Wjb9rKE0gSsIiCbqYWE+9y/v04yrVW0mKfQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752506491; c=relaxed/simple; bh=J3h0bzv+66l5Vs9eafGDJARdqv3+sQK6ZF2ENvt/3ao=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=LDo3COxIvmjWfCbcBuZMK34zQlsx9L+VO2qWYvr/b0WLoxvh23od+cpp19RI4Rk4Ih4CrqIjED+4W0c/ZMIZOscP4DSRFVfb7DU9hmgmMC1Ooesk99cfwGkCY6TqenSo9gbCJjournsWT1y9EqlksEg5B6dA9+Qep7RPwy8r9U8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NFspP8lE; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="NFspP8lE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 21068C4CEED; Mon, 14 Jul 2025 15:21:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752506491; bh=J3h0bzv+66l5Vs9eafGDJARdqv3+sQK6ZF2ENvt/3ao=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NFspP8lExdSkLPa6lXOanaUhJmwVlfQi/GCal5vgjXZqHppSz2xS7g/g+K1IUvdgB N4dl+zrFV5eV5OZMYl8EDjDMZ+hEj0gkB1WpcSeX2r1Ljgewo08+83Jd5DlGQxxL26 61/+jY0z7+Ub/L2TBd3juZmSUt1EgX0no/4bHeKjoxsHK19NUPdmHk5MhVL2jwIBpX 4bz4q3xUf1fbSLgMLmsS25z9mRSdE++0JGZ5Pd4UKGynIFRUmwmCZsspgO4YtEBpae DiydLS14INe/vl/i08Sz1AATZqiLeW9atahKEDm7ncy5Yr2gUoESsoCTzZtFr43G7T 1qIY6mIrQSZlA== From: Will Deacon To: linux-kernel@vger.kernel.org Cc: Will Deacon , Keir Fraser , Steven Moreland , Frederick Mayle , Stefan Hajnoczi , Stefano Garzarella , "Michael S. Tsirkin" , Jason Wang , =?UTF-8?q?Eugenio=20P=C3=A9rez?= , netdev@vger.kernel.org, virtualization@lists.linux.dev Subject: [PATCH v3 7/9] vhost/vsock: Allocate nonlinear SKBs for handling large receive buffers Date: Mon, 14 Jul 2025 16:21:01 +0100 Message-Id: <20250714152103.6949-8-will@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250714152103.6949-1-will@kernel.org> References: <20250714152103.6949-1-will@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When receiving a packet from a guest, vhost_vsock_handle_tx_kick() calls vhost_vsock_alloc_linear_skb() to allocate and fill an SKB with the receive data. Unfortunately, these are always linear allocations and can therefore result in significant pressure on kmalloc() considering that the maximum packet size (VIRTIO_VSOCK_MAX_PKT_BUF_SIZE + VIRTIO_VSOCK_SKB_HEADROOM) is a little over 64KiB, resulting in a 128KiB allocation for each packet. Rework the vsock SKB allocation so that, for sizes with page order greater than PAGE_ALLOC_COSTLY_ORDER, a nonlinear SKB is allocated instead with the packet header in the SKB and the receive data in the fragments. Finally, add a debug warning if virtio_vsock_skb_rx_put() is ever called on an SKB with a non-zero length, as this would be destructive for the nonlinear case. Signed-off-by: Will Deacon --- drivers/vhost/vsock.c | 8 +++----- include/linux/virtio_vsock.h | 40 +++++++++++++++++++++++++++++------- 2 files changed, 36 insertions(+), 12 deletions(-) diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c index 24b7547b05a6..0679a706ebc0 100644 --- a/drivers/vhost/vsock.c +++ b/drivers/vhost/vsock.c @@ -349,7 +349,7 @@ vhost_vsock_alloc_skb(struct vhost_virtqueue *vq, return NULL; /* len contains both payload and hdr */ - skb = virtio_vsock_alloc_linear_skb(len, GFP_KERNEL); + skb = virtio_vsock_alloc_skb(len, GFP_KERNEL); if (!skb) return NULL; @@ -378,10 +378,8 @@ vhost_vsock_alloc_skb(struct vhost_virtqueue *vq, virtio_vsock_skb_rx_put(skb, payload_len); - nbytes = copy_from_iter(skb->data, payload_len, &iov_iter); - if (nbytes != payload_len) { - vq_err(vq, "Expected %zu byte payload, got %zu bytes\n", - payload_len, nbytes); + if (skb_copy_datagram_from_iter(skb, 0, &iov_iter, payload_len)) { + vq_err(vq, "Failed to copy %zu byte payload\n", payload_len); kfree_skb(skb); return NULL; } diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h index 36dd0cd55368..fa5934ea9c81 100644 --- a/include/linux/virtio_vsock.h +++ b/include/linux/virtio_vsock.h @@ -49,20 +49,46 @@ static inline void virtio_vsock_skb_clear_tap_delivered(struct sk_buff *skb) static inline void virtio_vsock_skb_rx_put(struct sk_buff *skb, u32 len) { - skb_put(skb, len); + DEBUG_NET_WARN_ON_ONCE(skb->len); + + if (skb_is_nonlinear(skb)) + skb->len = len; + else + skb_put(skb, len); +} + +static inline struct sk_buff * +__virtio_vsock_alloc_skb_with_frags(unsigned int header_len, + unsigned int data_len, + gfp_t mask) +{ + struct sk_buff *skb; + int err; + + skb = alloc_skb_with_frags(header_len, data_len, + PAGE_ALLOC_COSTLY_ORDER, &err, mask); + if (!skb) + return NULL; + + skb_reserve(skb, VIRTIO_VSOCK_SKB_HEADROOM); + skb->data_len = data_len; + return skb; } static inline struct sk_buff * virtio_vsock_alloc_linear_skb(unsigned int size, gfp_t mask) { - struct sk_buff *skb; + return __virtio_vsock_alloc_skb_with_frags(size, 0, mask); +} - skb = alloc_skb(size, mask); - if (!skb) - return NULL; +static inline struct sk_buff *virtio_vsock_alloc_skb(unsigned int size, gfp_t mask) +{ + if (size <= SKB_WITH_OVERHEAD(PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) + return virtio_vsock_alloc_linear_skb(size, mask); - skb_reserve(skb, VIRTIO_VSOCK_SKB_HEADROOM); - return skb; + size -= VIRTIO_VSOCK_SKB_HEADROOM; + return __virtio_vsock_alloc_skb_with_frags(VIRTIO_VSOCK_SKB_HEADROOM, + size, mask); } static inline void -- 2.50.0.727.gbf7dc18ff4-goog