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FROMGIT: BACKPORT: vsock/virtio: Allocate nonlinear SKBs for handling large transmit buffers

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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 <sgarzare@redhat.com>
Signed-off-by: Will Deacon <will@kernel.org>
Message-Id: <20250717090116.11987-10-will@kernel.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(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 <willdeacon@google.com>
Change-Id: Icf2d6179ca7ac36383604ba6e0fd96a7f5a9c767
This commit is contained in:
Will Deacon
2025-07-17 10:01:16 +01:00
committed by Isaac Manjarres
parent 080548dfc3
commit 35ae5c9699
1 changed files with 3 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
net/vmw_vsock/virtio_transport_common.c
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@@ -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;