From: Catalin Marinas <catalin.marinas@arm.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Arnd Bergmann <arnd@arndb.de>, Christoph Hellwig <hch@lst.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>,
Isaac Manjarres <isaacmanjarres@google.com>,
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
Subject: Re: [PATCH v4 13/15] iommu/dma: Force bouncing if the size is not cacheline-aligned
Date: Fri, 19 May 2023 16:46:35 +0100 [thread overview]
Message-ID: <ZGeZ21UQAXvrMe/2@arm.com> (raw)
In-Reply-To: <ZGeBcLVFKpLdTveZ@arm.com>
On Fri, May 19, 2023 at 03:02:24PM +0100, Catalin Marinas wrote:
> On Fri, May 19, 2023 at 01:29:38PM +0100, Robin Murphy wrote:
> > On 2023-05-18 18:34, Catalin Marinas wrote:
> > > + sg_dma_mark_bounced(sg);
> >
> > I'd prefer to have iommu_dma_map_sg_swiotlb() mark the segments, since
> > that's in charge of the actual bouncing. Then we can fold the alignment
> > check into dev_use_swiotlb() (with the dev_is_untrusted() condition taking
> > priority), and sync/unmap can simply rely on sg_is_dma_bounced() alone.
>
> With this patch we only set the SG_DMA_BOUNCED on the first element of
> the sglist. Do you want to set this flag only on individual elements
> being bounced? It makes some sense in principle but the
> iommu_dma_unmap_sg() path would need to scan the list again to decide
> whether to go the swiotlb path.
>
> If we keep the SG_DMA_BOUNCED flag only on the first element, I can
> change it to your suggestion, assuming I understood it.
Can one call:
iommu_dma_map_sg(sg, nents);
...
iommu_dma_unmap_sg(sg + n, nents - n);
(i.e. unmap it in multiple steps)
If yes, setting SG_DMA_BOUNCED on the first element only won't work. I
don't find this an unlikely scenario, so we maybe we do have to walk the
list again in unmap to search for the flag.
--
Catalin
next prev parent reply other threads:[~2023-05-19 15:46 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-18 17:33 [PATCH v4 00/15] mm, dma, arm64: Reduce ARCH_KMALLOC_MINALIGN to 8 Catalin Marinas
2023-05-18 17:33 ` [PATCH v4 01/15] mm/slab: Decouple ARCH_KMALLOC_MINALIGN from ARCH_DMA_MINALIGN Catalin Marinas
2023-05-19 15:49 ` Catalin Marinas
2023-05-18 17:33 ` [PATCH v4 02/15] dma: Allow dma_get_cache_alignment() to return the smaller cache_line_size() Catalin Marinas
2023-05-20 5:42 ` Christoph Hellwig
2023-05-20 6:14 ` Christoph Hellwig
2023-05-20 10:34 ` Catalin Marinas
2023-05-18 17:33 ` [PATCH v4 03/15] mm/slab: Simplify create_kmalloc_cache() args and make it static Catalin Marinas
2023-05-18 17:33 ` [PATCH v4 04/15] mm/slab: Limit kmalloc() minimum alignment to dma_get_cache_alignment() Catalin Marinas
2023-05-18 17:33 ` [PATCH v4 05/15] drivers/base: Use ARCH_DMA_MINALIGN instead of ARCH_KMALLOC_MINALIGN Catalin Marinas
2023-05-19 9:41 ` Greg Kroah-Hartman
2023-05-18 17:33 ` [PATCH v4 06/15] drivers/gpu: " Catalin Marinas
2023-05-18 17:33 ` [PATCH v4 07/15] drivers/usb: " Catalin Marinas
2023-05-19 9:41 ` Greg Kroah-Hartman
2023-05-18 17:33 ` [PATCH v4 08/15] drivers/spi: " Catalin Marinas
2023-05-18 17:33 ` [PATCH v4 09/15] drivers/md: " Catalin Marinas
2023-05-18 17:33 ` [PATCH v4 10/15] arm64: Allow kmalloc() caches aligned to the smaller cache_line_size() Catalin Marinas
2023-05-18 17:33 ` [PATCH v4 11/15] scatterlist: Add dedicated config for DMA flags Catalin Marinas
2023-05-20 5:42 ` Christoph Hellwig
2023-05-18 17:34 ` [PATCH v4 12/15] dma-mapping: Force bouncing if the kmalloc() size is not cache-line-aligned Catalin Marinas
2023-05-20 5:44 ` Christoph Hellwig
2023-05-18 17:34 ` [PATCH v4 13/15] iommu/dma: Force bouncing if the size is not cacheline-aligned Catalin Marinas
2023-05-19 12:29 ` Robin Murphy
2023-05-19 14:02 ` Catalin Marinas
2023-05-19 15:46 ` Catalin Marinas [this message]
2023-05-19 17:09 ` Robin Murphy
2023-05-22 7:27 ` Catalin Marinas
2023-05-23 15:47 ` Robin Murphy
2023-05-18 17:34 ` [PATCH v4 14/15] mm: slab: Reduce the kmalloc() minimum alignment if DMA bouncing possible Catalin Marinas
2023-05-19 11:00 ` Catalin Marinas
2023-05-18 17:34 ` [PATCH v4 15/15] arm64: Enable ARCH_WANT_KMALLOC_DMA_BOUNCE for arm64 Catalin Marinas
2023-05-18 17:56 ` [PATCH v4 00/15] mm, dma, arm64: Reduce ARCH_KMALLOC_MINALIGN to 8 Linus Torvalds
2023-05-18 18:13 ` Ard Biesheuvel
2023-05-18 18:50 ` Catalin Marinas
2023-05-18 18:46 ` Catalin Marinas
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