Re: [RFC PATCH 04/12] riscv: Allow to dynamically define VA_BITS

[Alex Ghiti]

Le 1/5/21 à 7:06 AM, Anup Patel a écrit :
> On Tue, Jan 5, 2021 at 1:33 AM Alexandre Ghiti <alex@xxxxxxxx> wrote:
> > With 4-level page table folding at runtime, we don't know at compile time
> > the size of the virtual address space so we must set VA_BITS dynamically
> > so that sparsemem reserves the right amount of memory for struct pages.
> >
> > Signed-off-by: Alexandre Ghiti <alex@xxxxxxxx>
> > ---
> >   arch/riscv/Kconfig                 | 10 ----------
> >   arch/riscv/include/asm/pgtable.h   | 11 +++++++++--
> >   arch/riscv/include/asm/sparsemem.h |  6 +++++-
> >   3 files changed, 14 insertions(+), 13 deletions(-)
> >
> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > index 44377fd7860e..2979a44103be 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -122,16 +122,6 @@ config ZONE_DMA32
> >          bool
> >          default y if 64BIT
> >
> > -config VA_BITS
> > -       int
> > -       default 32 if 32BIT
> > -       default 39 if 64BIT
> > -
> > -config PA_BITS
> > -       int
> > -       default 34 if 32BIT
> > -       default 56 if 64BIT
> > -
> >   config PAGE_OFFSET
> >          hex
> >          default 0xC0000000 if 32BIT && MAXPHYSMEM_2GB
> > diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> > index 102b728ca146..c7973bfd65bc 100644
> > --- a/arch/riscv/include/asm/pgtable.h
> > +++ b/arch/riscv/include/asm/pgtable.h
> > @@ -43,8 +43,14 @@
> >    * struct pages to map half the virtual address space. Then
> >    * position vmemmap directly below the VMALLOC region.
> >    */
> > +#ifdef CONFIG_64BIT
> > +#define VA_BITS                39
> > +#else
> > +#define VA_BITS                32
> > +#endif
> > +
> >   #define VMEMMAP_SHIFT \
> > -       (CONFIG_VA_BITS - PAGE_SHIFT - 1 + STRUCT_PAGE_MAX_SHIFT)
> > +       (VA_BITS - PAGE_SHIFT - 1 + STRUCT_PAGE_MAX_SHIFT)
> >   #define VMEMMAP_SIZE   BIT(VMEMMAP_SHIFT)
> >   #define VMEMMAP_END    (VMALLOC_START - 1)
> >   #define VMEMMAP_START  (VMALLOC_START - VMEMMAP_SIZE)
> > @@ -83,6 +89,7 @@
> >   #endif /* CONFIG_64BIT */
> >
> >   #ifdef CONFIG_MMU
> > +
> >   /* Number of entries in the page global directory */
> >   #define PTRS_PER_PGD    (PAGE_SIZE / sizeof(pgd_t))
> >   /* Number of entries in the page table */
> > @@ -453,7 +460,7 @@ static inline int ptep_clear_flush_young(struct vm_area_struct *vma,
> >    * and give the kernel the other (upper) half.
> >    */
> >   #ifdef CONFIG_64BIT
> > -#define KERN_VIRT_START        (-(BIT(CONFIG_VA_BITS)) + TASK_SIZE)
> > +#define KERN_VIRT_START        (-(BIT(VA_BITS)) + TASK_SIZE)
> >   #else
> >   #define KERN_VIRT_START        FIXADDR_START
> >   #endif
> > diff --git a/arch/riscv/include/asm/sparsemem.h b/arch/riscv/include/asm/sparsemem.h
> > index 45a7018a8118..63acaecc3374 100644
> > --- a/arch/riscv/include/asm/sparsemem.h
> > +++ b/arch/riscv/include/asm/sparsemem.h
> > @@ -4,7 +4,11 @@
> >   #define _ASM_RISCV_SPARSEMEM_H
> >
> >   #ifdef CONFIG_SPARSEMEM
> > -#define MAX_PHYSMEM_BITS       CONFIG_PA_BITS
> > +#ifdef CONFIG_64BIT
> > +#define MAX_PHYSMEM_BITS       56
> > +#else
> > +#define MAX_PHYSMEM_BITS       34
> > +#endif /* CONFIG_64BIT */
> >   #define SECTION_SIZE_BITS      27
> >   #endif /* CONFIG_SPARSEMEM */
> >
> > --
> > 2.20.1
>
> Looks good to me.
>
> Reviewed-by: Anup Patel <anup@xxxxxxxxxxxxxx>

Thanks,

> Regards,
> Anup

Alex