[PATCH v3] riscv: set max_pfn to the PFN of the last page

[Guo Ren]

Hi Palmer & Vicent,

Please have a look at the patch:

https://lore.kernel.org/linux-riscv/20210121063117.3164494-1-guoren@kernel.org/T/#u

Seems our set_max_mapnr is wrong and it will make pfn_valid fault in
non-zero start-address.

On Tue, May 5, 2020 at 5:14 AM Palmer Dabbelt <palmer at dabbelt.com> wrote:
>
> On Sun, 26 Apr 2020 23:59:24 PDT (-0700), vincent.chen at sifive.com wrote:
> > The current max_pfn equals to zero. In this case, I found it caused users
> > cannot get some page information through /proc such as kpagecount in v5.6
> > kernel because of new sanity checks. The following message is displayed by
> > stress-ng test suite with the command "stress-ng --verbose --physpage 1 -t
> > 1" on HiFive unleashed board.
> >
> >  # stress-ng --verbose --physpage 1 -t 1
> >  stress-ng: debug: [109] 4 processors online, 4 processors configured
> >  stress-ng: info: [109] dispatching hogs: 1 physpage
> >  stress-ng: debug: [109] cache allocate: reducing cache level from L3 (too high) to L0
> >  stress-ng: debug: [109] get_cpu_cache: invalid cache_level: 0
> >  stress-ng: info: [109] cache allocate: using built-in defaults as no suitable cache found
> >  stress-ng: debug: [109] cache allocate: default cache size: 2048K
> >  stress-ng: debug: [109] starting stressors
> >  stress-ng: debug: [109] 1 stressor spawned
> >  stress-ng: debug: [110] stress-ng-physpage: started [110] (instance 0)
> >  stress-ng: error: [110] stress-ng-physpage: cannot read page count for address 0x3fd34de000 in /proc/kpagecount, errno=0 (Success)
> >  stress-ng: error: [110] stress-ng-physpage: cannot read page count for address 0x3fd32db078 in /proc/kpagecount, errno=0 (Success)
> >  ...
> >  stress-ng: error: [110] stress-ng-physpage: cannot read page count for address 0x3fd32db078 in /proc/kpagecount, errno=0 (Success)
> >  stress-ng: debug: [110] stress-ng-physpage: exited [110] (instance 0)
> >  stress-ng: debug: [109] process [110] terminated
> >  stress-ng: info: [109] successful run completed in 1.00s
> >  #
> >
> > After applying this patch, the kernel can pass the test.
> >
> >  # stress-ng --verbose --physpage 1 -t 1
> >  stress-ng: debug: [104] 4 processors online, 4 processors configured stress-ng: info: [104] dispatching hogs: 1 physpage
> >  stress-ng: info: [104] cache allocate: using defaults, can't determine cache details from sysfs
> >  stress-ng: debug: [104] cache allocate: default cache size: 2048K
> >  stress-ng: debug: [104] starting stressors
> >  stress-ng: debug: [104] 1 stressor spawned
> >  stress-ng: debug: [105] stress-ng-physpage: started [105] (instance 0) stress-ng: debug: [105] stress-ng-physpage: exited [105] (instance 0) stress-ng: debug: [104] process [105] terminated
> >  stress-ng: info: [104] successful run completed in 1.01s
> >  #
> >
> > Fixes: 0651c263c8e3 (RISC-V: Move setup_bootmem() to mm/init.c)
> > Cc: stable at vger.kernel.org
> >
> > Signed-off-by: Vincent Chen <vincent.chen at sifive.com>
> > Reviewed-by: Anup Patel <anup at brainfault.org>
> > Reviewed-by: Yash Shah <yash.shah at sifive.com>
> > Tested-by: Yash Shah <yash.shah at sifive.com>
> >
> > Changes since v1:
> > 1. Add Fixes line and Cc stable kernel
> > Changes since v2:
> > 1. Fix typo in Anup email address
> > ---
> >  arch/riscv/mm/init.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> > index fab855963c73..157924baa191 100644
> > --- a/arch/riscv/mm/init.c
> > +++ b/arch/riscv/mm/init.c
> > @@ -149,7 +149,8 @@ void __init setup_bootmem(void)
> >       memblock_reserve(vmlinux_start, vmlinux_end - vmlinux_start);
> >
> >       set_max_mapnr(PFN_DOWN(mem_size));
> > -     max_low_pfn = PFN_DOWN(memblock_end_of_DRAM());
> > +     max_pfn = PFN_DOWN(memblock_end_of_DRAM());
> > +     max_low_pfn = max_pfn;
> >
> >  #ifdef CONFIG_BLK_DEV_INITRD
> >       setup_initrd();
>
> I'm dropping the Fixes tag, as the actual bug goes back farther than that
> commit, that's just as far as it'll auto-apply.
>


-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/