From: Robin Murphy <robin.murphy@arm.com>
To: Christoph Hellwig <hch@lst.de>,
Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Cc: linux-kernel@vger.kernel.org,
Jeremy Linton <jeremy.linton@arm.com>,
iommu@lists.linux-foundation.org,
linux-rpi-kernel@lists.infradead.org,
David Rientjes <rientjes@google.com>
Subject: Re: [PATCH] dma-pool: use single atomic pool for both DMA zones
Date: Wed, 8 Jul 2020 17:20:16 +0100 [thread overview]
Message-ID: <304053c7-9f88-8830-3287-2496a4cb48cd@arm.com> (raw)
In-Reply-To: <20200708153635.GB26743@lst.de>
On 2020-07-08 16:36, Christoph Hellwig wrote:
> On Wed, Jul 08, 2020 at 12:35:34PM +0200, Nicolas Saenz Julienne wrote:
>>> Which allows me to switch between ACPI/DT on the machine. In DT mode it
>>> works fine now,
>>
>> Nice, would that count as a Tested-by from you?
>>
>>> but with ACPI I continue to have failures unless I
>>> disable CMA via cma=0 on the kernel command line.
>>
>> Yes, I see why, in atomic_pool_expand() memory is allocated from CMA without
>> checking its correctness. That calls for a separate fix. I'll try to think of
>> something.
>
> I think we need a dma_coherent_ok for the allocations from the
> pool and then fall back to the next better one to get started. And
> yes, CMA is a bit of a mess, that generally needs better checks.
Yeah, another thought that came to mind later is that iommu-dma can use
pages from any pool regardless of the device's DMA mask, so we could
stand to be a lot less restrictive in that case too.
Perhaps it is better to just bite the bullet, keep the straightforward
one-pool-per-zone setup, and implement the dma_coherent_ok() type
fallback logic. More complexity for dma_alloc_from_pool(), but
everything else stays nice and simple - lose the assumption that
dev_to_pool() can work for this and and just let callers pass an
allocation mask directly, and have dma_free_from_pool() simply check all
available pools.
Robin.
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
next prev parent reply other threads:[~2020-07-08 16:20 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-07 12:28 [PATCH] dma-pool: use single atomic pool for both DMA zones Nicolas Saenz Julienne
2020-07-07 22:08 ` Jeremy Linton
2020-07-08 10:35 ` Nicolas Saenz Julienne
2020-07-08 15:11 ` Jeremy Linton
2020-07-08 15:36 ` Christoph Hellwig
2020-07-08 16:20 ` Robin Murphy [this message]
2020-07-08 15:35 ` Christoph Hellwig
2020-07-08 16:00 ` Nicolas Saenz Julienne
2020-07-08 16:10 ` Christoph Hellwig
2020-07-09 21:49 ` David Rientjes via iommu
2020-07-10 8:19 ` Nicolas Saenz Julienne
2020-07-08 23:16 ` Jeremy Linton
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=304053c7-9f88-8830-3287-2496a4cb48cd@arm.com \
--to=robin.murphy@arm.com \
--cc=hch@lst.de \
--cc=iommu@lists.linux-foundation.org \
--cc=jeremy.linton@arm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-rpi-kernel@lists.infradead.org \
--cc=nsaenzjulienne@suse.de \
--cc=rientjes@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).