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Sun, 23 Jun 2024 17:12:44 -0700 (PDT) Message-ID: Date: Mon, 24 Jun 2024 01:12:46 +0100 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next v12 06/13] page_pool: devmem support To: Mina Almasry Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-alpha@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, sparclinux@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-arch@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Donald Hunter , Jonathan Corbet , Richard Henderson , Ivan Kokshaysky , Matt Turner , Thomas Bogendoerfer , "James E.J. Bottomley" , Helge Deller , Andreas Larsson , Sergey Shtylyov , Jesper Dangaard Brouer , Ilias Apalodimas , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Arnd Bergmann , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Steffen Klassert , Herbert Xu , David Ahern , Willem de Bruijn , Shuah Khan , Sumit Semwal , =?UTF-8?Q?Christian_K=C3=B6nig?= , Bagas Sanjaya , Christoph Hellwig , Nikolay Aleksandrov , David Wei , Jason Gunthorpe , Yunsheng Lin , Shailend Chand , Harshitha Ramamurthy , Shakeel Butt , Jeroen de Borst , Praveen Kaligineedi , linux-mm@kvack.org, Matthew Wilcox References: <20240613013557.1169171-1-almasrymina@google.com> <20240613013557.1169171-7-almasrymina@google.com> <439590d4-0f05-4f5e-80ec-e7fdf214e307@gmail.com> Content-Language: en-US From: Pavel Begunkov In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 6/21/24 19:48, Mina Almasry wrote: > On Mon, Jun 17, 2024 at 7:17 AM Pavel Begunkov wrote: ... >>> static inline unsigned long netmem_to_pfn(netmem_ref netmem) >>> { >>> + if (netmem_is_net_iov(netmem)) >>> + return 0; >> >> IIRC 0 is a valid pfn. Not much of a concern since it's >> used only for tracing, but might make sense to pass some >> invalid pfn if there is one >> > > AFAIU all non-negative pfns are technically valid pfns if the machine > is big enough. > > I could have this function return long long instead of unsigned long > so I can return a negative number for errors, and then cast to > unsigned long when I figure out it's actually a pfn. Seemed like such > a hassle especially since the call site is just tracing that I figured > it's not that worth it. Yeah, sounds like an overkill for tracing > >>> + >>> return page_to_pfn(netmem_to_page(netmem)); >>> } >>> >> ... >>> static inline netmem_ref netmem_compound_head(netmem_ref netmem) >>> { >>> + /* niov are never compounded */ >>> + if (netmem_is_net_iov(netmem)) >>> + return netmem; >>> + >>> return page_to_netmem(compound_head(netmem_to_page(netmem))); >>> } >>> >>> +static inline void *netmem_address(netmem_ref netmem) >> >> I don't think it's used anywhere, do I miss it? >> > > Ah, It's used by the GVE devmem implementation: > https://github.com/mina/linux/commit/da89baa81873d457cbf7b49ee6b4f0d66855b205 > > I could leave it out of this patch, then add it with the follow up GVE > devmem implementation, but I figured almost for sure drivers are going > to need this eventually, and it's small, so just put it here. Either way is fine by me, checking the function is not leftovers -- Pavel Begunkov