On Mon, Mar 13, 2017 at 07:50:21PM +0100, Borislav Petkov wrote: >On Fri, Feb 17, 2017 at 10:30:33PM +0800, Wei Yang wrote: >> In case (last_start <= step_size), start is for sure to be 0. So, it is >
Hmm, I may write it more specific:
"start" is for sure to be set to 0 with round_down(last_start - 1, step_size).
>Well, lemme see:
>
>[ 0.000000] memory_map_top_down: entry, [0x100000:0x7ffdf000)
>[ 0.000000] memory_map_top_down: addr: 0x7fc00000, real_end: 0x7fe00000
>[ 0.000000] memory_map_top_down: last_start: 0x40000000 <= step_size:
>0x2000000000, start: 0x40000000
>
> ^^^^^^^^^^
>It doesn't look like 0 to me.
>
>---
>diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
>index 2193799ca800..d3b02a416df3 100644
>--- a/arch/x86/mm/init.c
>+++ b/arch/x86/mm/init.c
>@@ -527,8 +531,13 @@ static void __init memory_map_top_down(unsigned long
>map_start,
> start = round_down(last_start - 1, step_size);
> if (start < map_start)
> start = map_start;
>- } else
>+ } else {
>+ pr_info("%s: last_start: 0x%lx <= step_size: 0x%lx,
>start: 0x%lx\n",
>+ __func__, last_start, step_size, start);
>+
If you change this log with the following
pr_err("%s: last_start: 0x%lx <= step_size: 0x%lx,
start: 0x%lx\n",
__func__, last_start, step_size,
round_down(last_start - 1, step_size));
You could see after calculation, start is 0 when (last_start <= step_size).
--
Wei Yang
Help you, Help me
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