linux-kernel - Re: [RFC PATCH v3 06/12] 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: <CAHS8izMGNLM18TF1RCDBfdOXXpqseePA4_27qmQt-FsrFzGfdQ@mail.gmail.com>
Date:   Sun, 12 Nov 2023 20:54:18 -0800
From:   Mina Almasry <almasrymina@...gle.com>
To:     Jakub Kicinski <kuba@...nel.org>
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,
        linaro-mm-sig@...ts.linaro.org,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.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>,
        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>
Subject: Re: [RFC PATCH v3 06/12] memory-provider: dmabuf devmem memory provider

On Fri, Nov 10, 2023 at 3:16 PM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Sun,  5 Nov 2023 18:44:05 -0800 Mina Almasry wrote:
> > +static int mp_dmabuf_devmem_init(struct page_pool *pool)
> > +{
> > +     struct netdev_dmabuf_binding *binding = pool->mp_priv;
> > +
> > +     if (!binding)
> > +             return -EINVAL;
> > +
> > +     if (pool->p.flags & PP_FLAG_DMA_MAP ||
> > +         pool->p.flags & PP_FLAG_DMA_SYNC_DEV)
> > +             return -EOPNOTSUPP;
>
> This looks backwards, we should _force_ the driver to use the dma
> mapping built into the page pool APIs, to isolate the driver from
> how the DMA addr actually gets obtained. Right?
>
> Maybe seeing driver patches would illuminate.

The full tree with driver patches is here:

https://github.com/torvalds/linux/compare/master...mina:linux:tcpdevmem-v3

This is probably the most relevant patch, it implements POC page-pool
support into GVE + devmem support:

https://github.com/torvalds/linux/commit/3c27aa21eb3374f2f1677ece6258f046da234443

But, to answer your question, yes, this is a mistake. devmem doesn't
need to be mapped, which is why I disabled the flag. Actually what
should happen is like you said, we should enforce that PP_FLAG_DMA_MAP
is on, and have it be a no-op, so the driver doesn't try to map the
devmem on its own.

-- 
Thanks,
Mina