From: Christoph Hellwig <hch@lst.de>
To: "Petr Tesařík" <petr@tesarici.cz>
Cc: Michael Kelley <mhklinux@outlook.com>,
Will Deacon <will@kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
Christoph Hellwig <hch@lst.de>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Petr Tesarik <petr.tesarik1@huawei-partners.com>,
"kernel-team@android.com" <kernel-team@android.com>,
"iommu@lists.linux.dev" <iommu@lists.linux.dev>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Dexuan Cui <decui@microsoft.com>,
Nicolin Chen <nicolinc@nvidia.com>
Subject: Re: [PATCH v5 6/6] swiotlb: Remove pointless stride adjustment for allocations >= PAGE_SIZE
Date: Tue, 5 Mar 2024 15:08:33 +0100 [thread overview]
Message-ID: <20240305140833.GC3659@lst.de> (raw)
In-Reply-To: <20240304200428.4111d78e@meshulam.tesarici.cz>
On Mon, Mar 04, 2024 at 08:04:28PM +0100, Petr Tesařík wrote:
> Sure, this will solve the allocations. But my understanding of this
> same thread is that we don't need it here. The historical page order
> alignment applies ONLY to allocations, NOT to mappings. It is
> documented in Documentation/core-api/dma-api-howto.rst under Consistent
> DMA mappings, for dma_alloc_coherent(). IIUC it does not apply to the
> streaming DMA mappings. At least, it would explain why nobody
> complained that the more strict guarantee for sizes greater than
> PAGE_SIZE was not kept...
Yes. arm32 (and before the dma-direct conversion various other
architectures) have relaxed the required to a PAGE_SIZE alignment,
and at least no native dma direct has ever returned less than PAGE_SIZE
alignment even for smaller allocations (as they are all rounded up
to PAGE_SIZE). So I think the documentation could also use some
updating to match reality.
next prev parent reply other threads:[~2024-03-05 14:08 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-28 13:39 [PATCH v5 0/6] Fix double allocation in swiotlb_alloc() Will Deacon
2024-02-28 13:39 ` [PATCH v5 1/6] swiotlb: Fix double-allocation of slots due to broken alignment handling Will Deacon
2024-02-29 5:44 ` Michael Kelley
2024-02-28 13:39 ` [PATCH v5 2/6] swiotlb: Enforce page alignment in swiotlb_alloc() Will Deacon
2024-02-28 13:39 ` [PATCH v5 3/6] swiotlb: Honour dma_alloc_coherent() " Will Deacon
2024-02-28 13:39 ` [PATCH v5 4/6] swiotlb: Fix alignment checks when both allocation and DMA masks are present Will Deacon
2024-02-28 13:39 ` [PATCH v5 5/6] iommu/dma: Force swiotlb_max_mapping_size on an untrusted device Will Deacon
2024-02-29 5:57 ` Michael Kelley
2024-02-28 13:39 ` [PATCH v5 6/6] swiotlb: Remove pointless stride adjustment for allocations >= PAGE_SIZE Will Deacon
2024-02-29 6:07 ` Michael Kelley
2024-02-29 7:36 ` Michael Kelley
2024-02-29 13:33 ` Christoph Hellwig
2024-02-29 15:44 ` Michael Kelley
2024-02-29 15:47 ` Christoph Hellwig
2024-03-01 15:39 ` Petr Tesařík
2024-03-01 16:38 ` Robin Murphy
2024-03-01 17:33 ` Petr Tesařík
2024-03-01 17:08 ` Petr Tesařík
2024-03-01 17:54 ` Robin Murphy
2024-03-01 18:42 ` Petr Tesařík
2024-03-04 3:31 ` Michael Kelley
2024-03-04 11:00 ` Petr Tesařík
2024-03-04 13:37 ` Robin Murphy
2024-03-04 15:55 ` Petr Tesařík
2024-03-04 16:02 ` Will Deacon
2024-03-04 16:10 ` Michael Kelley
2024-03-04 16:53 ` Robin Murphy
2024-03-04 18:22 ` Michael Kelley
2024-03-05 11:20 ` Robin Murphy
2024-03-05 15:15 ` Petr Tesařík
2024-03-04 19:04 ` Petr Tesařík
2024-03-05 14:08 ` Christoph Hellwig [this message]
2024-03-04 16:04 ` Michael Kelley
2024-03-04 17:11 ` Robin Murphy
2024-03-04 18:08 ` Michael Kelley
2024-03-05 14:05 ` Christoph Hellwig
2024-03-04 15:32 ` Will Deacon
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