Subject: Re: [PATCH net-next] virtio_net: sync RX buffer before reading the header

From: [email-masked]
Date: Fri, 27 Mar 2026 03:20:14 +0000

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <[email-masked]>:

On Tue, 24 Mar 2026 11:15:54 -0400 you wrote:
> receive_buf() reads the virtio header through buf before
> page_pool_dma_sync_for_cpu() runs in receive_small() or
> receive_mergeable(). The header buffer is thus unsynchronized at the
> point where flags and, for mergeable buffers, num_buffers are consumed.
> 
> Omar Elghoul reported that on s390x Secure Execution this showed up as
> greatly reduced virtio-net performance together with "bad gso" and
> "bad csum" messages in dmesg. This is because with SE sync actually
> copies data, so the header is uninitialized.
> 
> [...]

Here is the summary with links:
  - [net-next] virtio_net: sync RX buffer before reading the header
    https://git.kernel.org/netdev/net-next/c/fe3e54253f0b

You are awesome, thank you!
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