Am 19.09.2017 um 19:20 schrieb Tom St Denis: > 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. Why do you think there isn't any translation on CZ? I mean the whole ATC thing uses the IOMMU (v2 in this case) on APUs. >> 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). Yeah, please do this for now. I mean it would be great to have this interface even with IOMMU disabled, but of hand I can't think of a way to allow this. Christian. > > Tom
