From 35ae5c96990dd9eb0b9236e4f5c387e44a00f823 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Thu, 17 Jul 2025 10:01:16 +0100 Subject: [PATCH] FROMGIT: BACKPORT: vsock/virtio: Allocate nonlinear SKBs for handling large transmit buffers When transmitting a vsock packet, virtio_transport_send_pkt_info() calls virtio_transport_alloc_linear_skb() to allocate and fill SKBs with the transmit 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 transmit data in the fragments. Note that this affects both the vhost and virtio transports. Reviewed-by: Stefano Garzarella Signed-off-by: Will Deacon Message-Id: <20250717090116.11987-10-will@kernel.org> Signed-off-by: Michael S. Tsirkin (cherry picked from commit c7991b44d7b44f9270dec63acd0b2965d29aab43 git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git vhost) Bug: 421244320 [willdeacon@: Inline skb_copy_datagram_from_iter() call due to missing zero-copy support and therefore missing definition of virtio_transport_fill_skb()] Signed-off-by: Will Deacon Change-Id: Icf2d6179ca7ac36383604ba6e0fd96a7f5a9c767 --- net/vmw_vsock/virtio_transport_common.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c index a561738c3c95..9e630e0f5cf7 100644 --- a/net/vmw_vsock/virtio_transport_common.c +++ b/net/vmw_vsock/virtio_transport_common.c @@ -59,10 +59,9 @@ virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *info, const size_t skb_len = VIRTIO_VSOCK_SKB_HEADROOM + len; struct virtio_vsock_hdr *hdr; struct sk_buff *skb; - void *payload; int err; - skb = virtio_vsock_alloc_linear_skb(skb_len, GFP_KERNEL); + skb = virtio_vsock_alloc_skb(skb_len, GFP_KERNEL); if (!skb) return NULL; @@ -79,8 +78,8 @@ virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *info, hdr->fwd_cnt = cpu_to_le32(0); if (info->msg && len > 0) { - payload = skb_put(skb, len); - err = memcpy_from_msg(payload, info->msg, len); + virtio_vsock_skb_put(skb, len); + err = skb_copy_datagram_from_iter(skb, 0, &info->msg->msg_iter, len); if (err) goto out;