Re: [PATCH net] net: mana: Sync page pool RX frags for CPU

[Simon Horman]

On Wed, Jun 17, 2026 at 08:50:29PM -0700, Dexuan Cui wrote:
> MANA allocates RX buffers from page pool fragments when frag_count is
> greater than 1. In that case the buffers remain DMA mapped by page pool
> and the RX completion path does not call dma_unmap_single(). As a result,
> the implicit sync-for-CPU normally performed by dma_unmap_single() is
> missing before the packet data is passed to the networking stack.
> 
> This breaks RX on configurations which require explicit DMA syncing, for
> example when booted with swiotlb=force.
> 
> Fix this by recording the page pool page and DMA sync offset when the RX
> buffer is allocated, and syncing the received packet range for CPU access
> before handing the RX buffer to the stack.
> 
> Also validate the packet length reported in the RX CQE before using it as
> a DMA sync length or passing it to skb processing. The CQE is supplied
> by the device and should not be blindly trusted by Confidential VMs.

I think this last part warrants being split out into a separate patch.

> 
> Fixes: 730ff06d3f5c ("net: mana: Use page pool fragments for RX buffers instead of full pages to improve memory efficiency.")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Dexuan Cui <decui@xxxxxxxxxxxxx>

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