linux-kernel - Re: [RFC PATCH 1/4] tee: Re-enable vmalloc page support for shared memory

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Message-ID: <ZHCoJEkVinvsB2lZ@infradead.org>
Date:   Fri, 26 May 2023 05:37:56 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Arnaud POULIQUEN <arnaud.pouliquen@...s.st.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Jens Wiklander <jens.wiklander@...aro.org>,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org,
        linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        op-tee@...ts.trustedfirmware.org
Subject: Re: [RFC PATCH 1/4] tee: Re-enable vmalloc page support for shared
 memory

On Wed, May 24, 2023 at 04:01:14PM +0200, Arnaud POULIQUEN wrote:
> > As per the discussion back then: don't just blindly do the same dumb
> > thing again and fix the interfae to actually pass in a page array,
> > or iov_iter or an actually useful container that fits.
> > 
> 
> I suppose your are speaking about this discussion:
> https://lore.kernel.org/all/20221002002326.946620-3-ira.weiny@intel.com/

Yes.

> 
> If I'm not mistaken, I should modify at tee_shm_register_kernel_buf API and
> register_shm_helper inernal function, right?
> 

> What about having equivalent of shm_get_kernel_pages in an external helper (to
> defined where to put it), could it be an alternative of the upadate of the
> tee_shm API?

I think the fundamentally right thing is to pass an iov_iter to
register_shm_helper, and then use the new as of 6.3
iov_iter_extract_pages helper to extract the pages from that.  For
the kernel users you can then simply pass down an ITER_BVEC iter
that you can fill with vmalloc pages if you want.