linux-kernel - Re: [PATCH] of: fdt: modify small size memory check

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Date: Mon, 4 Mar 2024 11:05:22 -0600
From: Rob Herring <robh+dt@...nel.org>
To: skseofh@...il.com
Cc: devicetree@...r.kernel.org, frowand.list@...il.com, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] of: fdt: modify small size memory check

On Mon, Mar 4, 2024 at 9:03 AM <skseofh@...il.com> wrote:
>
>
> >>
> >> From: Daero Lee <skseofh@...il.com>
> >>
> >> After page aligning, the size may become zero. So I added exception
> >> handling code for size 0.
> >
> >That may be true, but when would anyone only have memory regions of
> >less than 2 pages. In any case memblock_add will just do nothing. What
> >is the actual problem you are having?
> >
> >Rob
>
> Ignore the previous mail.
> I modified the patch to clear this size check routine. Please check

You still haven't answered my questions above.

Though the patch below is a bit more readable than what we currently have...

>
> -------------------------------------------------------------------------
> From 2135d37c37f8c369033f79102b17ddf5bb3ff838 Mon Sep 17 00:00:00 2001
> From: Daero Lee <skseofh@...il.com>
> Date: Mon, 4 Mar 2024 23:21:14 +0900
> Subject: [PATCH] of: fdt: modify small size memory check
>
> Small size memory which is less than 1 PAGE_SIZE after page align
> should not be added to memblock.
>
> In this patch, the size check was modified to make it clear.
>
> Signed-off-by: Daero Lee <skseofh@...il.com>
> ---
>  drivers/of/fdt.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index bf502ba8da95..9cf844e664b0 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -1220,18 +1220,16 @@ int __init early_init_dt_scan_chosen(char *cmdline)
>  void __init __weak early_init_dt_add_memory_arch(u64 base, u64 size)
>  {
>         const u64 phys_offset = MIN_MEMBLOCK_ADDR;
> +       u64 abase = PAGE_ALIGN(base), aend = PAGE_ALIGN_DOWN(base + size);
>
> -       if (size < PAGE_SIZE - (base & ~PAGE_MASK)) {
> +       if((aend - abase) < PAGE_SIZE) {
>                 pr_warn("Ignoring memory block 0x%llx - 0x%llx\n",
>                         base, base + size);
>                 return;
>         }
>
> -       if (!PAGE_ALIGNED(base)) {
> -               size -= PAGE_SIZE - (base & ~PAGE_MASK);
> -               base = PAGE_ALIGN(base);
> -       }
> -       size &= PAGE_MASK;
> +       base = abase;
> +       size = (aend - abase) & PAGE_MASK;
>
>         if (base > MAX_MEMBLOCK_ADDR) {
>                 pr_warn("Ignoring memory block 0x%llx - 0x%llx\n",
> --
> 2.25.1
>
>