Message-ID: <7c6d35e3-165f-5883-1c1b-fce82c976028@huawei.com>
Date: Fri, 22 Dec 2023 14:42:23 +0800
From: Yunsheng Lin <linyunsheng@...wei.com>
To: Mina Almasry <almasrymina@...gle.com>
CC: Shakeel Butt <shakeelb@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
	<linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
	<bpf@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar
	<mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen
	<dave.hansen@...ux.intel.com>, <x86@...nel.org>, "H. Peter Anvin"
	<hpa@...or.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J.
 Wysocki" <rafael@...nel.org>, Sumit Semwal <sumit.semwal@...aro.org>,
	Christian König <christian.koenig@....com>, Michael Chan
	<michael.chan@...adcom.com>, "David S. Miller" <davem@...emloft.net>, Eric
 Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Alexei
 Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Jesper
 Dangaard Brouer <hawk@...nel.org>, John Fastabend <john.fastabend@...il.com>,
	Wei Fang <wei.fang@....com>, Shenwei Wang <shenwei.wang@....com>, Clark Wang
	<xiaoning.wang@....com>, NXP Linux Team <linux-imx@....com>, Jeroen de Borst
	<jeroendb@...gle.com>, Praveen Kaligineedi <pkaligineedi@...gle.com>,
	Shailend Chand <shailend@...gle.com>, Yisen Zhuang <yisen.zhuang@...wei.com>,
	Salil Mehta <salil.mehta@...wei.com>, Jesse Brandeburg
	<jesse.brandeburg@...el.com>, Tony Nguyen <anthony.l.nguyen@...el.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>, Marcin Wojtas
	<mw@...ihalf.com>, Russell King <linux@...linux.org.uk>, Sunil Goutham
	<sgoutham@...vell.com>, Geetha sowjanya <gakula@...vell.com>, Subbaraya
 Sundeep <sbhatta@...vell.com>, hariprasad <hkelam@...vell.com>, Felix Fietkau
	<nbd@....name>, John Crispin <john@...ozen.org>, Sean Wang
	<sean.wang@...iatek.com>, Mark Lee <Mark-MC.Lee@...iatek.com>, Lorenzo
 Bianconi <lorenzo@...nel.org>, Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, Saeed
 Mahameed <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>, Horatiu
 Vultur <horatiu.vultur@...rochip.com>, <UNGLinuxDriver@...rochip.com>, "K. Y.
 Srinivasan" <kys@...rosoft.com>, Haiyang Zhang <haiyangz@...rosoft.com>, Wei
 Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>, Jassi Brar
	<jaswinder.singh@...aro.org>, Ilias Apalodimas <ilias.apalodimas@...aro.org>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>, Jose Abreu
	<joabreu@...opsys.com>, Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Siddharth Vadapalli <s-vadapalli@...com>, Ravi Gunasekaran
	<r-gunasekaran@...com>, Roger Quadros <rogerq@...nel.org>, Jiawen Wu
	<jiawenwu@...stnetic.com>, Mengyuan Lou <mengyuanlou@...-swift.com>, Ronak
 Doshi <doshir@...are.com>, VMware PV-Drivers Reviewers
	<pv-drivers@...are.com>, Ryder Lee <ryder.lee@...iatek.com>, Shayne Chen
	<shayne.chen@...iatek.com>, Kalle Valo <kvalo@...nel.org>, Juergen Gross
	<jgross@...e.com>, Stefano Stabellini <sstabellini@...nel.org>, Oleksandr
 Tyshchenko <oleksandr_tyshchenko@...m.com>, Andrii Nakryiko
	<andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu
	<song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>, KP Singh
	<kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>, Hao Luo
	<haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, Stefan Hajnoczi
	<stefanha@...hat.com>, Stefano Garzarella <sgarzare@...hat.com>, Shuah Khan
	<shuah@...nel.org>, Mickaël Salaün <mic@...ikod.net>,
	Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers
	<ndesaulniers@...gle.com>, Bill Wendling <morbo@...gle.com>, Justin Stitt
	<justinstitt@...gle.com>, Jason Gunthorpe <jgg@...dia.com>, Willem de Bruijn
	<willemdebruijn.kernel@...il.com>
Subject: Re: [RFC PATCH net-next v1 4/4] net: page_pool: use netmem_t instead
 of struct page in API

On 2023/12/22 5:22, Mina Almasry wrote:
> On Thu, Dec 21, 2023 at 3:32 AM Yunsheng Lin <linyunsheng@...wei.com> wrote:
>>
>> On 2023/12/20 11:01, Mina Almasry wrote:
>>
>> ...
>>
>>>>>> Perhaps we should aim to not export netmem_to_page(),
>>>>>> prevent modules from accessing it directly.
>>>>>
>>>>> +1.
>>>>
>>>
>>> I looked into this, but it turns out it's a slightly bigger change
>>> that needs some refactoring to make it work. There are few places
>>> where I believe I need to add netmem_to_page() that are exposed to the
>>> drivers via inline helpers, these are:
>>>
>>> - skb_frag_page(), which returns NULL if the netmem is not a page, but
>>> needs to do a netmem_to_page() to return the page otherwise.
>>
>> Is it possible to introduce something like skb_frag_netmem() for
>> netmem? so that we can keep most existing users of skb_frag_page()
>> unchanged and avoid adding additional checking overhead for existing
>> users.
>>
> 
> In my experience most current skb_frag_page() users need specifically
> the struct page*. Example is illegal_highdma() which
> PageHighMem(skb_frag_page())

For illegal_highdma() case, is it possible to use something like
skb_readabe_frag() checking to avoid calling skb_frag_page() for netmem?

> 
> But RFC v5 adds skb_frag_netmem() for callsites that want a netmem and
> don't care about specifically a page:
> 
> https://patchwork.kernel.org/project/netdevbpf/patch/20231218024024.3516870-10-almasrymina@google.com/
> 
>>> - The helpers inside skb_add_rx_frag(), which needs to do a
>>> netmem_to_page() to set skb->pfmemalloc.
>>
>> Similar as above, perhaps introduce something like skb_add_rx_netmem_frag()?
>>
> 
> Yes, v3 of this series adds skb_add_rx_frag_netmem():
> 
> https://patchwork.kernel.org/project/netdevbpf/patch/20231220214505.2303297-4-almasrymina@google.com/

Powered by blists - more mailing lists