Re: why do we still need bootmem allocator?

[Rob Herring]

On Wed, Jun 27, 2018 at 5:27 AM Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> wrote:
>
> Hi,
>
> On Mon, Jun 25, 2018 at 10:09:41AM -0600, Rob Herring wrote:
> > On Mon, Jun 25, 2018 at 8:08 AM Michal Hocko <mhocko@xxxxxxxxxx> wrote:
> > >
> > > Hi,
> > > I am wondering why do we still keep mm/bootmem.c when most architectures
> > > already moved to nobootmem. Is there any fundamental reason why others
> > > cannot or this is just a matter of work?
> >
> > Just because no one has done the work. I did a couple of arches
> > recently (sh, microblaze, and h8300) mainly because I broke them with
> > some DT changes.
>
> I've tried running the current upstream on h8300 gdb simulator and it
> failed:

It seems my patch[1] is still not applied. The maintainer said he applied it.

> [    0.000000] BUG: Bad page state in process swapper  pfn:00004
> [    0.000000] page:007ed080 count:0 mapcount:-128 mapping:00000000
> index:0x0
> [    0.000000] flags: 0x0()
> [    0.000000] raw: 00000000 0040bdac 0040bdac 00000000 00000000 00000002
> ffffff7f 00000000
> [    0.000000] page dumped because: nonzero mapcount
> ---Type <return> to continue, or q <return> to quit---
> [    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.18.0-rc2+ #50
> [    0.000000] Stack from 00401f2c:
> [    0.000000]   00401f2c 001116cb 007ed080 00401f40 000e20e6 00401f54
> 0004df14 00000000
> [    0.000000]   007ed080 007ed000 00401f5c 0004df8c 00401f90 0004e982
> 00000044 00401fd1
> [    0.000000]   007ed000 007ed000 00000000 00000004 00000008 00000000
> 00000003 00000011
> [    0.000000]
> [    0.000000] Call Trace:
> [    0.000000]         [<000e20e6>] [<0004df14>] [<0004df8c>] [<0004e982>]
> [    0.000000]         [<00051a28>] [<00001000>] [<00000100>]
> [    0.000000] Disabling lock debugging due to kernel taint
>
> With v4.13 I was able to get to "no valid init found".
>
> I had a quick look at h8300 memory initialization and it seems it has
> starting pfn set to 0 while fdt defines memory start at 4M.

Perhaps there's another issue.

Rob

[1] https://patchwork.kernel.org/patch/10290317/