Re: [PATCH 3/4] ARM: change vmalloc_min to vmalloc_start

["Xu, Yanfei" <yanfei.xu@windriver.com>]

On 5/18/21 8:15 PM, Russell King (Oracle) wrote:
> [Please note: This e-mail is from an EXTERNAL e-mail address]
> 
> Change the current vmalloc_min, which is supposed to be the lowest
> address of vmalloc space including the VMALLOC_OFFSET, to vmalloc_start
> which does not include VMALLOC_OFFSET.
> 
> Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
> ---
>   arch/arm/mm/mmu.c | 10 +++++-----
>   1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> index d932c46a02e0..457203b41ceb 100644
> --- a/arch/arm/mm/mmu.c
> +++ b/arch/arm/mm/mmu.c
> @@ -1123,8 +1123,7 @@ void __init debug_ll_io_init(void)
>   }
>   #endif
> 
> -static unsigned long __initdata vmalloc_min =
> -       VMALLOC_END - (240 << 20) - VMALLOC_OFFSET;
> +static unsigned long __initdata vmalloc_start = VMALLOC_END - (240 << 20);
> 
>   /*
>    * vmalloc=size forces the vmalloc area to be exactly 'size'
> @@ -1142,14 +1141,14 @@ static int __init early_vmalloc(char *arg)
>                          vmalloc_reserve >> 20);
>          }
> 
> -       vmalloc_max = VMALLOC_END - (PAGE_OFFSET + SZ_32M);
> +       vmalloc_max = VMALLOC_END - (PAGE_OFFSET + SZ_32M + VMALLOC_OFFSET);
>          if (vmalloc_reserve > vmalloc_max) {
>                  vmalloc_reserve = vmalloc_max;
>                  pr_warn("vmalloc area is too big, limiting to %luMB\n",
>                          vmalloc_reserve >> 20);
>          }
> 
> -       vmalloc_min = VMALLOC_END - vmalloc_reserve;
> +       vmalloc_start = VMALLOC_END - vmalloc_reserve;
>          return 0;
>   }
>   early_param("vmalloc", early_vmalloc);

The minimal vamlloc size should reduce 8MB, to be same with the original 
vmalloc size.

@@ -1133,8 +1133,8 @@ static int __init early_vmalloc(char *arg)
         unsigned long vmalloc_reserve = memparse(arg, NULL);
         unsigned long vmalloc_max;

-       if (vmalloc_reserve < SZ_16M) {
-               vmalloc_reserve = SZ_16M;
+       if (vmalloc_reserve < SZ_8M) {
+               vmalloc_reserve = SZ_8M;
                 pr_warn("vmalloc area too small, limiting to %luMB\n",
                         vmalloc_reserve >> 20);
         }

Another point, the current size of "vmalloc=" will be align up with 8MB, 
should we align it down? The original is align down when we consider the 
vmalloc_offest in vmalloc size. If yes, we could do it like

index eb6173315291..1fc2696fadd2 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -1133,8 +1133,9 @@ static int __init early_vmalloc(char *arg)
         unsigned long vmalloc_reserve = memparse(arg, NULL);
         unsigned long vmalloc_max;

-       if (vmalloc_reserve < SZ_16M) {
-               vmalloc_reserve = SZ_16M;
+       vmalloc_reserve = ALIGN_DOWN(vmalloc_reserve, SZ_8M);
+       if (vmalloc_reserve < SZ_8M) {
+               vmalloc_reserve = SZ_8M;
                 pr_warn("vmalloc area too small, limiting to %luMB\n",
                         vmalloc_reserve >> 20);
         }


Regards,
Yanfei


> @@ -1169,7 +1168,8 @@ void __init adjust_lowmem_bounds(void)
>           * and may itself be outside the valid range for which phys_addr_t
>           * and therefore __pa() is defined.
>           */
> -       vmalloc_limit = (u64)vmalloc_min - PAGE_OFFSET + PHYS_OFFSET;
> +       vmalloc_limit = (u64)vmalloc_start -
> +                       (PAGE_OFFSET + PHYS_OFFSET + VMALLOC_OFFSET);
> 
>          /*
>           * The first usable region must be PMD aligned. Mark its start
> --
> 2.20.1
> 

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