[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <b1476f8e-1b4b-497a-9e80-aff679ca8b4b@davidwei.uk>
Date: Wed, 8 Nov 2023 17:00:39 -0800
From: David Wei <dw@...idwei.uk>
To: David Ahern <dsahern@...nel.org>, Mina Almasry <almasrymina@...gle.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arch@...r.kernel.org, linux-kselftest@...r.kernel.org,
linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Jesper Dangaard Brouer <hawk@...nel.org>,
Ilias Apalodimas <ilias.apalodimas@...aro.org>, Arnd Bergmann
<arnd@...db.de>, Willem de Bruijn <willemdebruijn.kernel@...il.com>,
Shuah Khan <shuah@...nel.org>, Sumit Semwal <sumit.semwal@...aro.org>,
Christian König <christian.koenig@....com>,
Shakeel Butt <shakeelb@...gle.com>, Jeroen de Borst <jeroendb@...gle.com>,
Praveen Kaligineedi <pkaligineedi@...gle.com>,
Willem de Bruijn <willemb@...gle.com>, Kaiyuan Zhang <kaiyuanz@...gle.com>,
Pavel Begunkov <asml.silence@...il.com>
Subject: Re: [RFC PATCH v3 05/12] netdev: netdevice devmem allocator
On 2023-11-07 14:55, David Ahern wrote:
> On 11/7/23 3:10 PM, Mina Almasry wrote:
>> On Mon, Nov 6, 2023 at 3:44 PM David Ahern <dsahern@...nel.org> wrote:
>>>
>>> On 11/5/23 7:44 PM, Mina Almasry wrote:
>>>> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>>>> index eeeda849115c..1c351c138a5b 100644
>>>> --- a/include/linux/netdevice.h
>>>> +++ b/include/linux/netdevice.h
>>>> @@ -843,6 +843,9 @@ struct netdev_dmabuf_binding {
>>>> };
>>>>
>>>> #ifdef CONFIG_DMA_SHARED_BUFFER
>>>> +struct page_pool_iov *
>>>> +netdev_alloc_devmem(struct netdev_dmabuf_binding *binding);
>>>> +void netdev_free_devmem(struct page_pool_iov *ppiov);
>>>
>>> netdev_{alloc,free}_dmabuf?
>>>
>>
>> Can do.
>>
>>> I say that because a dmabuf can be host memory, at least I am not aware
>>> of a restriction that a dmabuf is device memory.
>>>
>>
>> In my limited experience dma-buf is generally device memory, and
>> that's really its use case. CONFIG_UDMABUF is a driver that mocks
>> dma-buf with a memfd which I think is used for testing. But I can do
>> the rename, it's more clear anyway, I think.
>
> config UDMABUF
> bool "userspace dmabuf misc driver"
> default n
> depends on DMA_SHARED_BUFFER
> depends on MEMFD_CREATE || COMPILE_TEST
> help
> A driver to let userspace turn memfd regions into dma-bufs.
> Qemu can use this to create host dmabufs for guest framebuffers.
>
>
> Qemu is just a userspace process; it is no way a special one.
>
> Treating host memory as a dmabuf should radically simplify the io_uring
> extension of this set. That the io_uring set needs to dive into
> page_pools is just wrong - complicating the design and code and pushing
> io_uring into a realm it does not need to be involved in.
I think our io_uring proposal will already be vastly simplified once we
rebase onto Kuba's page pool memory provider API. Using udmabuf means
depending on a driver designed for testing, vs io_uring's registered
buffers API that's been tried and tested.
I don't have an intuitive understanding of the trade offs yet, and would
need to try out udmabuf and compare vs say using our own page pool
memory provider.
>
> Most (all?) of this patch set can work with any memory; only device
> memory is unreadable.
>
>
Powered by blists - more mailing lists