on 2024/10/25 0:04, Simon Horman wrote:

On Thu, Oct 24, 2024 at 04:31:46PM +0800, Jijie Shao wrote:

quoted

on 2024/10/24 16:26, Paolo Abeni wrote:

quoted

On 10/18/24 12:10, Jijie Shao wrote:

quoted

From: Peiyang Wang <redacted>

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 <redacted>
Signed-off-by: Jian Shen <shenjian15@huawei.com>
Signed-off-by: Jijie Shao <shaojijie@huawei.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.