netdev - Re: [PATCH net-next v4 8/8] bnxt_en: add support for device memory tcp

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Message-ID: <5e6974f1-3a8f-42c0-8925-22c7e9c44cf0@davidwei.uk>
Date: Tue, 18 Feb 2025 16:15:56 -0800
From: David Wei <dw@...idwei.uk>
To: Taehee Yoo <ap420073@...il.com>, Mina Almasry <almasrymina@...gle.com>
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Subject: Re: [PATCH net-next v4 8/8] bnxt_en: add support for device memory
 tcp

On 2024-11-01 11:24, Taehee Yoo wrote:
> On Fri, Nov 1, 2024 at 11:53 PM Mina Almasry <almasrymina@...gle.com> wrote:
>>
>> On Tue, Oct 22, 2024 at 9:25 AM Taehee Yoo <ap420073@...il.com> wrote:
>>>
>>> Currently, bnxt_en driver satisfies the requirements of Device memory
>>> TCP, which is tcp-data-split.
>>> So, it implements Device memory TCP for bnxt_en driver.
>>>
>>> From now on, the aggregation ring handles netmem_ref instead of page
>>> regardless of the on/off of netmem.
>>> So, for the aggregation ring, memory will be handled with the netmem
>>> page_pool API instead of generic page_pool API.
>>>
>>> If Devmem is enabled, netmem_ref is used as-is and if Devmem is not
>>> enabled, netmem_ref will be converted to page and that is used.
>>>
>>> Driver recognizes whether the devmem is set or unset based on the
>>> mp_params.mp_priv is not NULL.
>>> Only if devmem is set, it passes PP_FLAG_ALLOW_UNREADABLE_NETMEM.
>>
>> Looks like in the latest version, you pass
>> PP_FLAG_ALLOW_UNREADABLE_NETMEM unconditionally, so this line is
>> obsolete.
> 
> Okay, I will remove this line.
> 
>>
>> However, I think you should only pass PP_FLAG_ALLOW_UNREADABLE_NETMEM
>> if hds_thresh==0 and tcp-data-split==1, because otherwise the driver
>> is not configured well enough to handle unreadable netmem, right? I
>> know that we added checks in the devmem binding to detect hds_thresh
>> and tcp-data-split, but we should keep another layer of protection in
>> the driver. The driver should not set PP_FLAG_ALLOW_UNREADABLE_NETMEM
>> unless it's configured to be able to handle unreadable netmem.
> 
> Okay, I agree, I will pass PP_FLAG_ALLOW_UNREADABLE_NETMEM
> only when hds_thresh==0 and tcp-data-split==1.
> 
>>
>>>
>>> Tested-by: Stanislav Fomichev <sdf@...ichev.me>
>>> Signed-off-by: Taehee Yoo <ap420073@...il.com>
>>> ---
>>>
>>> v4:
>>>  - Do not select NET_DEVMEM in Kconfig.
>>>  - Pass PP_FLAG_ALLOW_UNREADABLE_NETMEM flag unconditionally.
>>>  - Add __bnxt_rx_agg_pages_xdp().
>>>  - Use gfp flag in __bnxt_alloc_rx_netmem().
>>>  - Do not add *offset in the __bnxt_alloc_rx_netmem().
>>>  - Do not pass queue_idx to bnxt_alloc_rx_page_pool().
>>>  - Add Test tag from Stanislav.
>>>  - Add page_pool_recycle_direct_netmem() helper.
>>>
>>> v3:
>>>  - Patch added.
>>>
>>>  drivers/net/ethernet/broadcom/bnxt/bnxt.c | 182 ++++++++++++++++------
>>>  drivers/net/ethernet/broadcom/bnxt/bnxt.h |   2 +-
>>>  include/net/page_pool/helpers.h           |   6 +
>>>  3 files changed, 142 insertions(+), 48 deletions(-)

Hi Taehee, what is your plan with this patch? Are you still working on
it? I noticed that you dropped it in later versions of this series. With
io_uring zero copy Rx now merged I also need bnxt support, but I don't
want to duplicate efforts. Please let me know, thanks!