+CC arcml Hi Alexey, On 05/05/2017 01:44 AM, Alexey Brodkin wrote: > Hi Vineet, > > Playing with PAE40 on axs103 v1.2-rc2 (where PAE really seems to work quite well) > Eugeniy bumped into the fact that PAE could be enabled without HIGHMEM. > > Personally I din't face that trouble because I used to enable HIGHMEM manually before > even thinking of PAE. > > So we were surprised why there's no dependency which I was pretty sure was there > back in the day. And to no surprise I found you removed such a dependency in > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7cab91b87dd8eeee5911ec34be8bb0288ebba18b > "ARCv2: Allow enabling PAE40 w/o HIGHMEM". > > Now what we have another [and this time real HW] platform with PAE support > and DDR mapped above 4Gb do you think we may revert this change and > put dependency on HIGHMEM for PAE? > > If you like I may send a patch to that effect. I understand your point, and PAE40 when really exercising > 32 bits certainly needs HIGHMEM. However in a setup where we only had 32 bit paddr, we can technically still build a PAE40 enabled kernel - which uses PAE40 enabled MMU cmds etc (with upper words always happening to be 0) and should in theory work as well. Agreed it is not a production config, still it is a useful "test" config or a "developer" config. The next question is why was Euginey seeing the errors - because he had DT setup memory > 1_0000_0000 and CONFIG_HIGHMEM was not enabled ? That certainly is broken and needs to be prevented at config or early run time. -Vineet
