Re: [PATCH RFC] mips: bootmem: Don't use memory holes for page bitmap

[Ralf Baechle <ralf@linux-mips.org>]

On Thu, Jul 02, 2015 at 05:16:01PM +0200, Alexander Sverdlin wrote:

> Commit f9a7febd leads to a fact that mapstart and therefore a page bitmap for
> bootmem allocator immediately follows initrd_end. This doesn't always work
> well on Octeon, where there are holes in PFN ranges (refer to 5b3b1688 and
> 4MB-aligned PFN allocation). Depending on the inird location it could happen,
> that mapstart would be in an area not allocated by plat_mem_setup() in
> arch/mips/cavium-octeon/setup.c, but in the alignment hole between initrd and
> the next PFN area. Later on this memory will be unconditionally made available
> to buddy allocator at the end of free_all_bootmem_core() (mm/bootmem.c).
> All of this results in Linux using the memory not designated for Linux in
> Octeon's plat_mem_setup(), which in turn means corruption of the memory used
> by another OS/baremetal code on the same SoC.
> 
> It doesn't look to me as a problem of Octeon platform code, but rather as an
> inability of f9a7febd to deal correctly with the fragmented memory-mappings.
> Proposed fix moves the check for initrd address to the same calculation-loop
> in bootmem_init() (arch/mips/kernel/setup.c), which also accounts for kernel
> code location. This should result in mapstart located starting from the first
> PFN area after kernel code AND initrd.
> 
> Signed-off-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>

Appears reasonable.  Applied.

Thanks,

  Ralf