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
