On Fri, 4 Mar 2022, Thomas Bogendoerfer wrote: > > > With this patch, when add "mem=3G" to the command-line, the > > > kernel boots successfully, we can see the following messages: > > > > unfortunately this patch would break platforms without memory detection, > > which simply use mem=32M for memory configuration. Not sure how many > > rely on this mechanism. If we can make sure nobody uses it, I'm fine > > with your patch. > > maybe we could add a CONFIG option, which will be selected by > platforms, which don't need/want this usermem thing. FWIW I don't understand what the issue is here beyond that we have a bug that causes a system to hang when "mem=3G" is passed on the kernel command line. That is assuming that system does have contiguous RAM available for the kernel to use from address 0 up to 3GiB; otherwise it's a user error to tell the kernel it has that memory available (I did get bitten by that myself too): garbage in, garbage out. I think having a CONFIG option automatically selected to disable the ability to give a memory map override would handicap people in debugging their systems or working around firmware bugs, so I would rather be against it. Maciej
