From: Christoph Hellwig <hch@lst.de>
To: Robin Murphy <robin.murphy@arm.com>
Cc: David Gibson <david@gibson.dropbear.id.au>,
Ram Pai <linuxram@us.ibm.com>,
linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
linuxppc-dev@lists.ozlabs.org,
virtualization@lists.linux-foundation.org,
benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@ozlabs.org,
mdroth@linux.vnet.ibm.com, aik@linux.ibm.com,
paul.burton@mips.com, b.zolnierkie@samsung.com,
m.szyprowski@samsung.com, hch@lst.de, jasowang@redhat.com,
andmike@us.ibm.com, sukadev@linux.vnet.ibm.com
Subject: Re: [PATCH 1/2] dma-mapping: Add dma_addr_is_phys_addr()
Date: Tue, 15 Oct 2019 09:31:04 +0200 [thread overview]
Message-ID: <20191015073104.GA32252@lst.de> (raw)
In-Reply-To: <37609731-5539-b906-aa94-2ef0242795ac@arm.com>
On Mon, Oct 14, 2019 at 11:29:24AM +0100, Robin Murphy wrote:
>> However, I would like to see the commit message (and maybe the inline
>> comments) expanded a bit on what the distinction here is about. Some
>> of the text from the next patch would be suitable, about DMA addresses
>> usually being in a different address space but not in the case of
>> bounce buffering.
>
> Right, this needs a much tighter definition. "DMA address happens to be a
> valid physical address" is true of various IOMMU setups too, but I can't
> believe it's meaningful in such cases.
>
> If what you actually want is "DMA is direct or SWIOTLB" - i.e. "DMA address
> is physical address of DMA data (not necessarily the original buffer)" -
> wouldn't dma_is_direct() suffice?
It would. But drivers have absolutely no business knowing any of this.
next prev parent reply other threads:[~2019-10-15 7:31 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-12 1:25 [PATCH 0/2] virtio: Support encrypted memory on powerpc secure guests Ram Pai
2019-10-12 1:25 ` [PATCH 1/2] dma-mapping: Add dma_addr_is_phys_addr() Ram Pai
2019-10-12 1:25 ` [PATCH 2/2] virtio_ring: Use DMA API if memory is encrypted Ram Pai
2019-10-14 4:52 ` David Gibson
2019-10-15 7:35 ` Christoph Hellwig
2019-10-16 7:55 ` Ram Pai
2019-10-17 2:33 ` Jason Wang
2019-10-21 8:36 ` David Gibson
2019-10-14 4:51 ` [PATCH 1/2] dma-mapping: Add dma_addr_is_phys_addr() David Gibson
2019-10-14 10:29 ` Robin Murphy
2019-10-15 7:30 ` Ram Pai
2019-10-15 7:31 ` Christoph Hellwig [this message]
2019-10-12 1:36 ` [PATCH 0/2] virtio: Support encrypted memory on powerpc secure guests Ram Pai
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