From: Christoph Hellwig <hch@lst.de>
To: "Koenig, Christian" <Christian.Koenig@amd.com>
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Subject: Re: [PATCH 0/6] drm+dma: cache support for arm, etc
Date: Thu, 15 Aug 2019 20:27:42 +0200 [thread overview]
Message-ID: <20190815182742.GA20859@lst.de> (raw)
In-Reply-To: <e3f73b3c-49d5-3c19-dfff-0a24b4617e50@amd.com>
On Thu, Aug 15, 2019 at 06:21:00PM +0000, Koenig, Christian wrote:
> > (2) Add support for DMA_ATTR_NO_KERNEL_MAPPING to this new API instead
> > of dma_alloc_attrs. The initial difference with that flag is just
> > that we allow highmem, but in the future we could also unmap this
> > memory from the kernel linear mapping entirely on architectures
> > where we can easily do that.
>
> Mhm, why would we want to do this?
To avoid the CPU misspeculating into this memory. For example NVMe SSDs
have a feature called host memory buffer that is a lot like your stolen
main ram for the GPU case. We currently hand the SSD a
DMA_ATTR_NO_KERNEL_MAPPING allocation if it requests such a buffer. If
possible we'd really like to make sure no speculative execution bug
(or intentional attacker with a kernel exploit for that matter) can easily
access that memory.
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next prev parent reply other threads:[~2019-08-15 18:27 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-14 21:59 [PATCH 0/6] drm+dma: cache support for arm, etc Rob Clark
2019-08-14 21:59 ` [PATCH 1/6] arm64: export arch_sync_dma_for_*() Rob Clark
2019-08-14 21:59 ` [PATCH 2/6] mips: " Rob Clark
2019-08-14 21:59 ` [PATCH 4/6] arm: add arch_sync_dma_for_*() Rob Clark
2019-08-15 6:51 ` [PATCH 0/6] drm+dma: cache support for arm, etc Christoph Hellwig
2019-08-15 13:54 ` Rob Clark
2019-08-15 17:53 ` Christoph Hellwig
2019-08-15 18:21 ` Koenig, Christian
2019-08-15 18:27 ` Christoph Hellwig [this message]
2019-08-16 21:04 ` Rob Clark
2019-08-19 5:23 ` Christoph Hellwig
2019-08-19 14:39 ` Rob Clark
[not found] <215e5cb7-0fcf-48db-a656-817054dde420@email.android.com>
2019-08-15 18:52 ` Christoph Hellwig
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