On Tue, Sep 10, 2019 at 10:10:49AM -0700, Rob Clark wrote:
On Tue, Sep 10, 2019 at 9:34 AM Robin Murphy robin.murphy@arm.com wrote:
On 06/09/2019 22:44, Rob Clark wrote:
NOTE that in discussion of previous revisions, RMRR came up. This is not really a replacement for RMRR (nor does RMRR really provide any more information than we already get from EFI GOP, or DT in the simplefb case). I also don't see how RMRR could help w/ SMMU handover of CB/SMR config (Bjorn's patchset[1]) without defining new tables.
The point of RMRR-like-things is that they identify not just the memory region but also the specific device accessing them, which means the IOMMU driver knows up-front which IDs etc. it must be careful not to disrupt. Obviously for SMMU that *would* be some new table (designed to encompass everything relevant) since literal RMRRs are specifically an Intel VT-d thing.
Perhaps I'm not looking in the right place, but the extent of what I could find about RMRR tables was:
https://github.com/tianocore/edk2/blob/master/MdePkg/Include/IndustryStandar...
I couldn't really see how that specifies the device. But entirely possible that I'm not seeing the whole picture.
I don't think anybody was planning to implement RMRR "as-is" for arm64, so you might be better off looking at the proposal from Thierry, although it has some issues that are still to be resolved:
http://lkml.kernel.org/r/20190829111407.17191-1-thierry.reding@gmail.com
Will