linux-kernel - Re: [PATCH V2 net 1/9] net: hns3: default enable tx bounce buffer when smmu enabled

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <977d1e83-b24b-4f4c-ad5b-8fb95f45d189@huawei.com>
Date: Fri, 25 Oct 2024 09:10:39 +0800
From: Jijie Shao <shaojijie@...wei.com>
To: Simon Horman <horms@...nel.org>
CC: <shaojijie@...wei.com>, Paolo Abeni <pabeni@...hat.com>,
	<davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
	<shenjian15@...wei.com>, <salil.mehta@...wei.com>, <liuyonglong@...wei.com>,
	<wangpeiyang1@...wei.com>, <lanhao@...wei.com>, <chenhao418@...wei.com>,
	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2 net 1/9] net: hns3: default enable tx bounce buffer
 when smmu enabled


on 2024/10/25 0:04, Simon Horman wrote:
> On Thu, Oct 24, 2024 at 04:31:46PM +0800, Jijie Shao wrote:
>> on 2024/10/24 16:26, Paolo Abeni wrote:
>>> On 10/18/24 12:10, Jijie Shao wrote:
>>>> From: Peiyang Wang <wangpeiyang1@...wei.com>
>>>>
>>>> The SMMU engine on HIP09 chip has a hardware issue.
>>>> SMMU pagetable prefetch features may prefetch and use a invalid PTE
>>>> even the PTE is valid at that time. This will cause the device trigger
>>>> fake pagefaults. The solution is to avoid prefetching by adding a
>>>> SYNC command when smmu mapping a iova. But the performance of nic has a
>>>> sharp drop. Then we do this workaround, always enable tx bounce buffer,
>>>> avoid mapping/unmapping on TX path.
>>>>
>>>> This issue only affects HNS3, so we always enable
>>>> tx bounce buffer when smmu enabled to improve performance.
>>>>
>>>> Signed-off-by: Peiyang Wang <wangpeiyang1@...wei.com>
>>>> Signed-off-by: Jian Shen <shenjian15@...wei.com>
>>>> Signed-off-by: Jijie Shao <shaojijie@...wei.com>
>>> I'm sorry to nick pick on somewhat small details, but we really need a
>>> fixes tag here to make 110% clear is a bugfix. I guess it could be the
>>> commit introducing the support for the buggy H/W.
>>>
>>> Thanks,
>>>
>>> Paolo
>> I have a little doubt that this patch is about H/W problem,
>> so how can we write the the fixes tag?
> Hi Jijie,
>
> That is a good point. But the much point of the Fixes tag is to indicate how
> far back the fix should be backported. So I would say the ID of the patch
> where the user would have first seen this problem - possibly the patch that
> added the driver.

That's a good idea. Thank you.