Re: [PATCH v3 13/13] dma: arm64: Add CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC and enable it for arm64

From: "Petr Tesařík" <petr@tesarici.cz>
To: Alexander Graf <agraf@csgraf.de>
Cc: Isaac Manjarres <isaacmanjarres@google.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Arnd Bergmann <arnd@arndb.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Ard Biesheuvel <ardb@kernel.org>,
	Saravana Kannan <saravanak@google.com>,
	Alasdair Kergon <agk@redhat.com>, Daniel Vetter <daniel@ffwll.ch>,
	Joerg Roedel <joro@8bytes.org>, Mark Brown <broonie@kernel.org>,
	Mike Snitzer <snitzer@kernel.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	linux-mm@kvack.org, iommu@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v3 13/13] dma: arm64: Add CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC and enable it for arm64
Date: Thu, 20 Apr 2023 13:51:24 +0200	[thread overview]
Message-ID: <20230420135124.62c452db@meshulam.tesarici.cz> (raw)
In-Reply-To: <629d62ce-b993-35fe-05ff-ee0befc0c73d@csgraf.de>

Hi Alex!

Nice to meet you again...

On Thu, 1 Dec 2022 00:32:07 +0100
Alexander Graf <agraf@csgraf.de> wrote:

> Hi Isaac,
> 
> On 30.11.22 19:48, Isaac Manjarres wrote:
> > On Tue, Nov 08, 2022 at 11:03:31AM +0100, Christoph Hellwig wrote:  
> >> On Tue, Nov 08, 2022 at 09:52:15AM +0000, Catalin Marinas wrote:  
> >>> Since it's hard to guess the optimal swiotlb buffer for such platforms,
> >>> I think a follow-up step would be to use the DMA coherent pool for
> >>> bouncing if no swiotlb buffer is available. At least the pool can grow
> >>> dynamically. Yet another option would be to increase the swiotlb buffer
> >>> at run-time but it has an overhead for is_swiotlb_buffer().  
> >> Alex said he wanted to look into growing the swiotlb buffer on demand
> >> for other reason, so adding him to Cc to check if there has been any
> >> progress on that.  
> > Hi Alex,
> >
> > Did you get a chance to look into this? If so, have you been able to
> > make progress on being able to grow the SWIOTLB buffer on demand?  
> 
> 
> I've been slightly under water and haven't been able to look at this yet 
> :). It's on my list, but will probably be a while until I get to it. 
> Would you be interested in having a first try?

All right, I have just found this thread now after having sent my own
patch series to make SWIOTLB dynamic. I hope you don't mind. I didn't
want to "steal" the project from you.

Petr T