Reverting seems like the right approach at the moment. My apologies for the breakage so late the in the cycle.
Post-revert, there remains a bug here wherein you can make the system OOPS if you mmap memory above the 48 bit bus width. Linus/Ingo, is there something in particular that you'd like to see before pulling in a check on the bus width (or some other fix)? Based on Linus' comment, the bus width check smells like something that should cook for a while before pulling into mainline. On Thu, Oct 26, 2017 at 1:29 PM, Linus Torvalds <torva...@linux-foundation.org> wrote: > On Thu, Oct 26, 2017 at 9:02 PM, Ingo Molnar <mi...@kernel.org> wrote: >> >> Well, 'mem=2048M' shouldn't really limit device memory, it's supposed to >> limit >> (trim) 'RAM' and not much else. > > Agreed. You should very much be able to map in IO memory or whatever > above the 2G address even if the high_memory itself might be limited > to 2GB. > > So I think that commit ce56a86e2ade ("x86/mm: Limit mmap() of /dev/mem > to valid physical addresses") is wrong, in that "high_memory" is very > much the wrong thing to test. > > The memory mapping limit might validly be something like > > 1ull << boot_cpu_data.x86_phys_bits > > or similar, but for now I suspect that the right thing to do is to > revert. I'm not convinced that our "x86_phys_bits" value is guaranteed > to be always right, since I think we mainlyjust use it for showing > things, rather than have lots of code that depends on it. > > Ingo? > > Linus