From: Simon Horman <horms@kernel.org>
To: Dexuan Cui <decui@microsoft.com>
Cc: kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org,
longli@microsoft.com, andrew+netdev@lunn.ch, davem@davemloft.net,
edumazet@google.com, kuba@kernel.org, pabeni@redhat.com,
kotaranov@microsoft.com, ernis@linux.microsoft.com,
dipayanroy@linux.microsoft.com, kees@kernel.org,
jacob.e.keller@intel.com, ssengar@linux.microsoft.com,
linux-hyperv@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH net] net: mana: Sync page pool RX frags for CPU
Date: Fri, 19 Jun 2026 10:05:14 +0100 [thread overview]
Message-ID: <20260619090514.GT827683@horms.kernel.org> (raw)
In-Reply-To: <20260618035029.249361-1-decui@microsoft.com>
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@vger.kernel.org
> Signed-off-by: Dexuan Cui <decui@microsoft.com>
...
prev parent reply other threads:[~2026-06-19 9:05 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-18 3:50 [PATCH net] net: mana: Sync page pool RX frags for CPU Dexuan Cui
2026-06-18 18:38 ` Haiyang Zhang
2026-06-19 9:05 ` Simon Horman [this message]
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