On Thu, 2008-08-14 at 01:20 -0700, David Miller wrote: > I just mentioned this to Ben H. on IRC and promised I would report it > here. :-) > > The first loop over lmb.memory in this function interprets the > memory_limit as a raw size limit, and that's fine so far. > > But the second loop over lmb.reserved interprets this value > instead as an "address limit." > > I haven't cobbled together a fix myself, but probably the way to do > this is, when we're about break out of the first loop over lmb.memory, > walk through the now-trimmed memory blobs and trim those from > lmb.reserved, one by one.
Perhaps after the first loop we should set memory_limit to equal lmb_end_of_DRAM(), then the second loop should work as it is. I think that actually makes memory_limit (the variable) more useful, and avoids more code like we have in numa_enforce_memory_limit(), which doesn't use memory_limit exactly because it isn't the value we're actually interested in (because of holes). > This bug got introduced by: > > commit 2babf5c2ec2f2d5de3e38d20f7df7fd815fd10c9 > Author: Michael Ellerman <[EMAIL PROTECTED]> > Date: Wed May 17 18:00:46 2006 +1000 > > [PATCH] powerpc: Unify mem= handling > > back when LMB was still a powerpc local item. :-) Guilty as charged. I have some tests for that code, but clearly not enough - and it gets very little exercise otherwise. > This led me to another bug which probably a lot of platforms are > effected by. > > If you do this command line memory limiting, and the kernel was placed > by the boot loader into physical ram (say at the end of the available > physical memory) that gets trimmed out by the command line option, we > hang or crash right as we boot into userspace because freeing up > initmem ends up freeing invalid page structs. > > I think, on sparc64, instead of adding all kinds of complicated logic > to free_initmem() I'm simply going to only poison the pages and > not free them at all if cmdline_memory_size has been set. Would it be that much extra logic to check that the address is less than the limit? Especially if we changed memory_limit to incorporate holes. cheers -- Michael Ellerman OzLabs, IBM Australia Development Lab wwweb: http://michael.ellerman.id.au phone: +61 2 6212 1183 (tie line 70 21183) We do not inherit the earth from our ancestors, we borrow it from our children. - S.M.A.R.T Person
signature.asc
Description: This is a digitally signed message part
_______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
