netdev - Re: [PATCH net 4/4] 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: <21993e23-9ac6-4108-94e6-752fe32a11d2@huawei.com>
Date: Tue, 8 Jul 2025 17:41:36 +0800
From: Jijie Shao <shaojijie@...wei.com>
To: Simon Horman <horms@...nel.org>
CC: <shaojijie@...wei.com>, <davem@...emloft.net>, <edumazet@...gle.com>,
	<kuba@...nel.org>, <pabeni@...hat.com>, <andrew+netdev@...n.ch>,
	<shenjian15@...wei.com>, <liuyonglong@...wei.com>, <chenhao418@...wei.com>,
	<jonathan.cameron@...wei.com>, <shameerali.kolothum.thodi@...wei.com>,
	<salil.mehta@...wei.com>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net 4/4] net: hns3: default enable tx bounce buffer when
 smmu enabled


on 2025/7/5 0:31, Simon Horman wrote:
> On Wed, Jul 02, 2025 at 09:09:01PM +0800, Jijie Shao wrote:
>> 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.
>>
>> Fixes: 295ba232a8c3 ("net: hns3: add device version to replace pci revision")
> The cited commit may be a pre-requisite for this patch
> to check HNAE3_DEVICE_VERSION_V3. But it seems to me that the problem
> being addressed existed before the cited commit. If so, I think a different
> Fixes tag is appropriate.
>
>> Signed-off-by: Jian Shen <shenjian15@...wei.com>
>> Signed-off-by: Jijie Shao <shaojijie@...wei.com>
>> ---
>>   .../net/ethernet/hisilicon/hns3/hns3_enet.c   | 31 +++++++++++++++++
>>   .../net/ethernet/hisilicon/hns3/hns3_enet.h   |  2 ++
>>   .../ethernet/hisilicon/hns3/hns3_ethtool.c    | 33 +++++++++++++++++++
> It seems to me that the hns3_ethtool.c changes a) are not a requirement
> for the work-around introduced by this patch and b) may introduce
> complex behaviour between the effect of ethtool copybreak settings
> and the enablement/non-enablement of the work-around.
>
> Would it be possible to make a more minimal fix for net, that
> omits the ethtool changes. And then follow-up with them for net-next
> once the fix is present there?

I will discuss your suggestion with my team.

Thanks
Jijie Shao