From: Christoph Hellwig <hch@lst.de>
To: Michael Kelley <mhklinux@outlook.com>
Cc: Will Deacon <will@kernel.org>,
"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>,
Christoph Hellwig <hch@lst.de>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Robin Murphy <robin.murphy@arm.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: Thu, 29 Feb 2024 14:33:46 +0100 [thread overview]
Message-ID: <20240229133346.GA7177@lst.de> (raw)
In-Reply-To: <SN6PR02MB41577D09E97B1D9645369D58D45F2@SN6PR02MB4157.namprd02.prod.outlook.com>
On Thu, Feb 29, 2024 at 07:36:05AM +0000, Michael Kelley wrote:
> If there *is* a requirement for page alignment of page-size-or-greater
> requests, even when alloc_align_mask and min_align_mask are zero,
> we need to think about how to do that correctly, as that requirement
> is no longer met after Patch 1 of this series.
It has been historical behavior that all dma allocations are page
aligned (including in fact smaller than page sized ones that get
rounded up to a page size). The documentation actually (incorretly)
states an even stronger guarantee:
"The CPU virtual address and the DMA address are both
guaranteed to be aligned to the smallest PAGE_SIZE order which
is greater than or equal to the requested size. This invariant
exists (for example) to guarantee that if you allocate a chunk
which is smaller than or equal to 64 kilobytes, the extent of the
buffer you receive will not cross a 64K boundary."
next prev parent reply other threads:[~2024-02-29 13:33 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 [this message]
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
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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