linux-kernel - Re: [net-next v1 08/16] memory-provider: dmabuf devmem memory provider

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <d17e203c-ee9f-44fc-8b03-bb34e80701e7@gmail.com>
Date:   Fri, 8 Dec 2023 23:05:49 +0000
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Mina Almasry <almasrymina@...gle.com>,
        Shailend Chand <shailend@...gle.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-kselftest@...r.kernel.org,
        bpf@...r.kernel.org, linux-media@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Jeroen de Borst <jeroendb@...gle.com>,
        Praveen Kaligineedi <pkaligineedi@...gle.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        David Ahern <dsahern@...nel.org>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Shuah Khan <shuah@...nel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        Yunsheng Lin <linyunsheng@...wei.com>,
        Harshitha Ramamurthy <hramamurthy@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Kaiyuan Zhang <kaiyuanz@...gle.com>
Subject: Re: [net-next v1 08/16] memory-provider: dmabuf devmem memory
 provider

On 12/8/23 00:52, Mina Almasry wrote:
> Implement a memory provider that allocates dmabuf devmem page_pool_iovs.
> 
> The provider receives a reference to the struct netdev_dmabuf_binding
> via the pool->mp_priv pointer. The driver needs to set this pointer for
> the provider in the page_pool_params.
> 
> The provider obtains a reference on the netdev_dmabuf_binding which
> guarantees the binding and the underlying mapping remains alive until
> the provider is destroyed.
> 
> Usage of PP_FLAG_DMA_MAP is required for this memory provide such that
> the page_pool can provide the driver with the dma-addrs of the devmem.
> 
> Support for PP_FLAG_DMA_SYNC_DEV is omitted for simplicity.
> 
> Signed-off-by: Willem de Bruijn <willemb@...gle.com>
> Signed-off-by: Kaiyuan Zhang <kaiyuanz@...gle.com>
> Signed-off-by: Mina Almasry <almasrymina@...gle.com>
[...]
> +void __page_pool_iov_free(struct page_pool_iov *ppiov);
> +
> +static inline void page_pool_iov_put_many(struct page_pool_iov *ppiov,
> +					  unsigned int count)
> +{
> +	if (!refcount_sub_and_test(count, &ppiov->refcount))
> +		return;
> +
> +	__page_pool_iov_free(ppiov);
> +}
> +
> +/* page pool mm helpers */
> +
> +DECLARE_STATIC_KEY_FALSE(page_pool_mem_providers);
> +static inline bool page_is_page_pool_iov(const struct page *page)
> +{
> +	return static_branch_unlikely(&page_pool_mem_providers) &&
> +	       (unsigned long)page & PP_IOV;

Are there any recommendations of not using static keys in widely
used inline functions? I'm not familiar with static key code
generation, but I think the compiler will bloat users with fat chunks
of code in unlikely paths. And I'd assume it creates an array of all
uses, which it'll be walked on enabling/disabling the branch.

> +}
> +
> +static inline struct page_pool_iov *page_to_page_pool_iov(struct page *page)
> +{
> +	if (page_is_page_pool_iov(page))
> +		return (struct page_pool_iov *)((unsigned long)page & ~PP_IOV);
> +
> +	DEBUG_NET_WARN_ON_ONCE(true);
> +	return NULL;
> +}
> +
>   /**
>    * page_pool_dev_alloc_pages() - allocate a page.
>    * @pool:	pool from which to allocate
-- 
Pavel Begunkov