linux-kernel - Re: [PATCH v3] tee: convert convert get_user_pages() --> pin_user

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Message-ID: <20200825083204.GA2068961@jade>
Date:   Tue, 25 Aug 2020 10:32:04 +0200
From:   Jens Wiklander <jens.wiklander@...aro.org>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     arm@...nel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, olof@...om.net, soc@...nel.org,
        tee-dev@...ts.linaro.org, Sumit Semwal <sumit.semwal@...aro.org>,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH v3] tee: convert convert get_user_pages() -->
 pin_user_pages()

On Mon, Aug 24, 2020 at 02:11:25PM -0700, John Hubbard wrote:
> This code was using get_user_pages*(), in a "Case 2" scenario
> (DMA/RDMA), using the categorization from [1]. That means that it's
> time to convert the get_user_pages*() + put_page() calls to
> pin_user_pages*() + unpin_user_pages() calls.
> 
> Factor out a new, small release_registered_pages() function, in
> order to consolidate the logic for discerning between
> TEE_SHM_USER_MAPPED and TEE_SHM_KERNEL_MAPPED pages. This also
> absorbs the kfree() call that is also required there.
> 
> There is some helpful background in [2]: basically, this is a small
> part of fixing a long-standing disconnect between pinning pages, and
> file systems' use of those pages.
> 
> [1] Documentation/core-api/pin_user_pages.rst
> 
> [2] "Explicit pinning of user-space pages":
>     https://lwn.net/Articles/807108/
> 
> Cc: Jens Wiklander <jens.wiklander@...aro.org>
> Cc: Sumit Semwal <sumit.semwal@...aro.org>
> Cc: tee-dev@...ts.linaro.org
> Cc: linux-media@...r.kernel.org
> Cc: dri-devel@...ts.freedesktop.org
> Cc: linaro-mm-sig@...ts.linaro.org
> Signed-off-by: John Hubbard <jhubbard@...dia.com>
> ---
> 
> OK, one more try, this time actually handling the _USER_MAPPED vs.
> _KERNEL_MAPPED pages!
> 
> thanks,
> John Hubbard
> NVIDIA

Looks good and it works too! :-) I've tested it on my Hikey board with
the OP-TEE test suite.
I'm picking this up.

Thanks,
Jens