linux-kernel - Re: [PATCH V2 net 2/9] net: hns3: add sync command to sync io-pgtable

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Message-ID: <214d37cc-96c0-4d47-bea0-3985e920d88c@redhat.com>
Date: Thu, 24 Oct 2024 10:36:45 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Jijie Shao <shaojijie@...wei.com>, davem@...emloft.net,
 edumazet@...gle.com, kuba@...nel.org, shenjian15@...wei.com,
 salil.mehta@...wei.com
Cc: 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 2/9] net: hns3: add sync command to sync io-pgtable

On 10/18/24 12:10, Jijie Shao wrote:
> From: Jian Shen <shenjian15@...wei.com>
> 
> To avoid errors in pgtable prefectch, add a sync command to sync
> io-pagtable.
> 
> In the case of large traffic, the TX bounce buffer may be used up.

It's unclear to me what do you mean for large traffic. Is that large
packets instead?

Skimming over the previous patch, it looks like the for the bugger H/W
driver will use the bounce buffer for all packets with len < 64K. As
this driver does not support big tcp, such condition means all packets.

So its not clear to me the 'may' part - it looks like the critical path
will always happen on the bugged H/W

> At this point, we go to mapping/unmapping on TX path again.
> So we added the sync command in driver to avoid hardware issue.

I thought the goal of the previous patch was to avoid such sync-up.

So I don't understand why it's there.

A more verbose explanation will help.

> Signed-off-by: Jian Shen <shenjian15@...wei.com>
> Signed-off-by: Peiyang Wang <wangpeiyang1@...wei.com>
> Signed-off-by: Jijie Shao <shaojijie@...wei.com>

Also we need a fixes tag.

Thanks,

Paolo