On 19/09/17 01:23 PM, Christian König wrote: > 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. On my Carrizo devel system (A12-9800) the GPU dma addresses are physical addresses. I only first saw iommu with APUs enabled on Raven. I'll see if I can read non-mapped pages via the iova file on my Carrizo. >>> 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. Sent to the list already. Tested with enabled/disabled. Seems to work for me. Tom
