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

Sasha Levin
2020-12-28T22:58:08Z

On Mon, Dec 28, 2020 at 10:54:23AM -0800, Jakub Kicinski wrote:
>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 :/

The timeline is usually for a commit to appear in a release, and it did.
Was it too early?

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

What do you mean with "queued"? Its in Linus's tree for about two weeks
now.

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

The autosel stuff is about 2-3(-4) weeks at this point, stuff with a
fixes tag gets picked up in about 2 weeks.

--
Thanks,
Sasha