Re: [PATCH 1/3] riscv: Fix memory_limit for 64-bit kernel

[Alex Ghiti]

Le 1/07/2021 à 21:01, Alex Ghiti a écrit :
> Le 1/07/2021 à 12:44, Kefeng Wang a écrit :
> > On 2021/6/29 17:13, Alexandre Ghiti wrote:
> > > As described in Documentation/riscv/vm-layout.rst, the end of the
> > > virtual address space for 64-bit kernel is occupied by the modules/BPF/
> > > kernel mappings so this actually reduces the amount of memory we are 
> > > able
> > > to map and then use in the linear mapping. So make sure this limit is
> > > correctly set.
> > >
> > > Fixes: c9811e379b21 ("riscv: Add mem kernel parameter support")
> >
> >
> > Should the Fixes tag be de043da0b9e7 （“RISC-V: Fix usage of 
> > memblock_enforce_memory_limit“）,
> >
> > The -PAGE_OFFSET is set to the maximal physical memory from this point :)
>
> Oops, thank you!

Actually the commit you mentioned was merged way before I moved the 
kernel to the end of the address space, so the proper Fixes tag should be:

Fixes: 2bfc6cd81bd1 ("riscv: Move kernel mapping outside of linear mapping")

Thanks anyway,

> Alex
>
> > > Signed-off-by: Alexandre Ghiti <alex@xxxxxxxx>
> > > ---
> > >   arch/riscv/mm/init.c | 11 +++++++++--
> > >   1 file changed, 9 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> > > index 12f956b3a674..04a5db3a9788 100644
> > > --- a/arch/riscv/mm/init.c
> > > +++ b/arch/riscv/mm/init.c
> > > @@ -124,10 +124,17 @@ void __init mem_init(void)
> > >   }
> > >   /*
> > > - * The default maximal physical memory size is -PAGE_OFFSET,
> > > - * limit the memory size via mem.
> > > + * The default maximal physical memory size is -PAGE_OFFSET for 
> > > 32-bit kernel,
> > > + * whereas for 64-bit kernel, the end of the virtual address space 
> > > is occupied
> > > + * by the modules/BPF/kernel mappings which reduces the available 
> > > size of the
> > > + * linear mapping.
> > > + * Limit the memory size via mem.
> > >    */
> > > +#ifdef CONFIG_64BIT
> > > +static phys_addr_t memory_limit = -PAGE_OFFSET - SZ_4G;
> > > +#else
> > >   static phys_addr_t memory_limit = -PAGE_OFFSET;
> > > +#endif
> > >   static int __init early_mem(char *p)
> > >   {
> >
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