[PATCH] riscv: Add support to allocate gigantic hugepages using CMA

[Alex Ghiti]

Hi Kefeng,

Le 29/07/2021 à 08:24, Kefeng Wang a écrit :
> The RV32 only has at most 1GB memory(MAXPHYSMEM_1GB), so let's
> disable HUGETLBFS on RV32.

There is only one size of hugepages for RV32 which is 4MB, there isn't 
any gigantic hugepage of 1GB: there are only 2 levels of page table, a 
PGDIR represents 4MB and this is the only way to have a hugepage on 
RV32. So I think we should leave hugetlbfs available on RV32.

Thanks,

Alex

> And add support to allocate gigantic
> hugepages using CMA by specifying the hugetlb_cma= kernel parameter.
> 
> Signed-off-by: Kefeng Wang <wangkefeng.wang at huawei.com>
> ---
>   arch/riscv/Kconfig   | 2 +-
>   arch/riscv/mm/init.c | 2 ++
>   2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 8fcceb8eda07..20a589605307 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -33,7 +33,7 @@ config RISCV
>   	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
>   	select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
>   	select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
> -	select ARCH_SUPPORTS_HUGETLBFS if MMU
> +	select ARCH_SUPPORTS_HUGETLBFS if MMU && 64BIT
>   	select ARCH_USE_MEMTEST
>   	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
>   	select ARCH_WANT_FRAME_POINTERS
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index a14bf3910eec..f2268402894b 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -19,6 +19,7 @@
>   #include <linux/set_memory.h>
>   #include <linux/dma-map-ops.h>
>   #include <linux/crash_dump.h>
> +#include <linux/hugetlb.h>
>   
>   #include <asm/fixmap.h>
>   #include <asm/tlbflush.h>
> @@ -216,6 +217,7 @@ static void __init setup_bootmem(void)
>   
>   	early_init_fdt_scan_reserved_mem();
>   	dma_contiguous_reserve(dma32_phys_limit);
> +	hugetlb_cma_reserve(PUD_SHIFT - PAGE_SHIFT);
>   	memblock_allow_resize();
>   }
>   
>