Re: [PATCH 5.10 462/717] ice, xsk: clear the status bits for the next_to_use descriptor

Jakub Kicinski
2020-12-28T18:55:27Z

On Mon, 28 Dec 2020 13:47:40 +0100 Greg Kroah-Hartman wrote:
> From: Björn Töpel <bjorn.topel@intel.com>
>
> [ Upstream commit 8d14768a7972b92c73259f0c9c45b969d85e3a60 ]
>
> On the Rx side, the next_to_use index points to the next item in the
> HW ring to be refilled/allocated, and next_to_clean points to the next
> item to potentially be processed.
>
> When the HW Rx ring is fully refilled, i.e. no packets has been
> processed, the next_to_use will be next_to_clean - 1. When the ring is
> fully processed next_to_clean will be equal to next_to_use. The latter
> case is where a bug is triggered.
>
> If the next_to_use bits are not cleared, and the "fully processed"
> state is entered, a stale descriptor can be processed.
>
> The skb-path correctly clear the status bit for the next_to_use
> descriptor, but the AF_XDP zero-copy path did not do that.
>
> This change adds the status bits clearing of the next_to_use
> descriptor.
>
> Fixes: 2d4238f55697 ("ice: Add support for AF_XDP")
> Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> Signed-off-by: Sasha Levin <sashal@kernel.org>

Oh wow, so much for Sasha waiting longer for code to get tested before
auto-pulling things into stable :/

I have this change and other changes here queued, but haven't sent the
submission yet.

How long is the auto-backporting delay in terms of calendar days?