On 19/09/17 01:18 PM, Christian König wrote:
Am 19.09.2017 um 19:14 schrieb Tom St Denis:
On 19/09/17 01:10 PM, Christian König wrote:
As far as I know we don't need #ifdefs cause there are dummy
functions when IOMMU is not compiled in.
But this patch is a NAK since it circumvents the /dev/mem restriction
when IOMMU is disabled and that is not something we can easily allow.
I raised this objection 24 hours ago and was told to go ahead with the
read/write methods anyways.
Short of making a list of mappings/allocations in the ttm layer I have
no idea how we would track this in the non-iommu case which means the
entire iova debugfs entry should have been NAK'ed in the first place.
I'm open to suggestions.
As long as IOMMU is enabled the entry is perfectly fine, cause only
memory mapped to the IOMMU is accessible to the GPU and so accessible
using the debugfs entry as well.
On devices where there's no translation (e.g. Carrizo) does the iommu
layer track mappings? I'm wondering if on those I could seek outside of
boundaries and read system memory anyways.
Only when IOMMU is disabled we can't go this way cause we can't know
which memory is mapped to the driver and which isn't (or could we
somehow track this?).
I suggest to not create the file in the first place if IOMMU is disabled.
I could easily do this (basically check if the domain is not null at
debugfs init time).
Tom
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