On 05/01/2021 09:13, Mike Rapoport wrote: > On Sun, Jan 03, 2021 at 03:09:14PM -0500, Andrea Arcangeli wrote: >> Hello Mike, >> >> On Sun, Jan 03, 2021 at 03:47:53PM +0200, Mike Rapoport wrote: >>> Thanks for the logs, it seems that implicitly adding reserved regions to >>> memblock.memory wasn't that bright idea :) >> >> Would it be possible to somehow clean up the hack then? >> >> The only difference between the clean solution and the hack is that >> the hack intended to achieved the exact same, but without adding the >> reserved regions to memblock.memory. > > I didn't consider adding reserved regions to memblock.memory as a clean > solution, this was still a hack, but I didn't think that things are that > fragile. > > I still think we cannot rely on memblock.reserved to detect > memory/zone/node sizes and the boot failure reported here confirms this. > >> The comment on that problematic area says the reserved area cannot be >> used for DMA because of some unexplained hw issue, and that doing so >> prevents booting, but since the area got reserved, even with the clean >> solution, it shouldn't have never been used for DMA? >> >> So I can only imagine that the physical memory region is way more >> problematic than just for DMA. It sounds like that anything that >> touches it, including the CPU, will hang the system, not just DMA. It >> sounds somewhat similar to the other e820 direct mapping issue on x86? > > My understanding is that the boot failed because when I implicitly added > the reserved region to memblock.memory the memory size seen by > free_area_init() jumped from 2G to 4G because the reserved area was close > to 4G. The very first allocation would get a chunk from slightly below of > 4G and as there is no real memory there, the kernel would crash. > >> If you want to test the hack on the arm board to check if it boots you >> can use the below commit: >> >> https://git.kernel.org/pub/scm/linux/kernel/git/andrea/aa.git/commit/?id=c3ea2633015104ce0df33dcddbc36f57de1392bc > > My take is your solution would boot with this memory configuration, but I > still don't think that using memblock.reserved for zone/node sizing is > correct. The rk3288 platform has now been failing to boot for nearly a month on linux-next: https://kernelci.org/test/case/id/5ffbed0a31ad81239bc94cdb/ Until a fix or a new version of this patch is made, would it be possible to drop it or revert it so the platform become usable again? Or if you want, I can make a cleaned-up version of my hack to ignore the problematic region if you still need your patch to be on linux-next, but that would probably be less than ideal. Thanks, Guillaume
