From: joro@8bytes•org (Joerg Roedel)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v5 1/3] iommu: Implement common IOMMU ops for DMA mapping
Date: Tue, 11 Aug 2015 11:37:42 +0200 [thread overview]
Message-ID: <20150811093742.GC14980@8bytes.org> (raw)
In-Reply-To: <55C4B4DF.4040608@arm.com>
On Fri, Aug 07, 2015 at 02:38:39PM +0100, Robin Murphy wrote:
> Indeed, DMA_DEBUG will check that a driver is making DMA API calls
> to the arch code in the right way; this is a different check, to
> catch things like the arch code passing the wrong domain into this
> layer, or someone else having messed directly with the domain via
> the IOMMU API. If the iommu_unmap doesn't match the IOVA region we
> looked up, that means the IOMMU page tables have somehow become
> inconsistent with the IOVA allocator, so we are in an unrecoverable
> situation where we can no longer be sure what devices have access
> to. That's bad.
Sure, but the BUG_ON would also trigger on things like a double-free,
which is bad to handle as a BUG_ON. A WARN_ON for this is sufficient.
> AFAIK, yes (this is just a slight tidyup of the existing code that
> 32-bit Exynos/Tegra/Rockchip/etc. devices are already using) - the
> display guys want increasingly massive contiguous allocations for
> framebuffers, layers, etc., so having IOMMU magic deal with that
> saves CMA for non-IOMMU devices that really need it.
Makes sense, I thougt about something similar for x86 too to avoid the
high-order allocations we currently do. I guess the buffer will later be
mapped into the vmalloc space for the CPU?
Joerg
next prev parent reply other threads:[~2015-08-11 9:37 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-31 17:18 [PATCH v5 0/3] arm64: IOMMU-backed DMA mapping Robin Murphy
2015-07-31 17:18 ` [PATCH v5 1/3] iommu: Implement common IOMMU ops for " Robin Murphy
2015-08-03 17:40 ` Catalin Marinas
2015-08-06 15:23 ` Will Deacon
2015-08-06 17:54 ` joro at 8bytes.org
2015-08-07 8:42 ` Joerg Roedel
2015-08-07 13:38 ` Robin Murphy
2015-08-11 9:37 ` Joerg Roedel [this message]
2015-08-11 13:31 ` Robin Murphy
2015-07-31 17:18 ` [PATCH v5 2/3] arm64: Add IOMMU dma_ops Robin Murphy
2015-08-03 17:33 ` Catalin Marinas
2015-08-07 8:52 ` Joerg Roedel
2015-08-07 15:27 ` Robin Murphy
2015-08-11 9:49 ` Joerg Roedel
2015-08-11 20:15 ` Robin Murphy
2015-09-22 17:12 ` Daniel Kurtz
2015-09-22 18:11 ` Robin Murphy
2015-07-31 17:18 ` [PATCH v5 3/3] arm64: Hook up " Robin Murphy
2015-08-07 8:55 ` Joerg Roedel
2015-08-26 6:19 ` [PATCH v5 0/3] arm64: IOMMU-backed DMA mapping Yong Wu
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