On Thu, Mar 09, 2023 at 01:45:05PM +0100, Alexandre Ghiti wrote: > > On 3/7/23 12:35, Mike Rapoport wrote: > > Hi Conor, > > > > Sorry for the delay, somehow this slipped between the cracks. > > > > On Thu, Feb 02, 2023 at 10:01:26PM +0000, Conor Dooley wrote: > > > Hullo Palmer, Mike & whoever else may read this, > > > > > > Just reviving this thread from a little while ago as I have been in the > > > area again recently... > > TBH, I didn't really dig deep into the issues, but the thought I had was > > what if DT was mapped via fixmap until the setup_vm_final() and then it > > would be possible to call DT methods early. > > > > Could be I'm shooting in the dark :) > > > I think I understand the issue now, it's because In riscv, we establish 2 > different virtual mappings and we map the device tree at 2 different virtual > addresses, which is the problem. > > So to me, the solution is: > > - to revert your previous fix, that is calling > early_init_fdt_scan_reserved_mem() before any call to memblock_alloc() > (which could result in an allocation in the area you want to reserve) > > - to map the device tree at the same virtual address, because > early_init_fdt_scan_reserved_mem() initializes reserved_mem with the dtb > mapping established in setup_vm() and uses reserved_mem with the new mapping > from setup_vm_final (which is what Mike proposes, we should use the fixmap > region to have the same virtual addresses) > > Hope that makes sense: I'll come up with something this afternoon for you to > test! Sounds good. Please give me some ELI5 commit messages if you can, explanations for this stuff (which I found took a lot of archaeology to understand) would be very welcome next time we need to go back looking at this stuff. Thanks Alex! Conor.
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