Messages in this thread | | | Date | Tue, 14 Mar 2017 11:56:39 +0800 | From | Wei Yang <> | Subject | Re: [PATCH] x86/mm: trivial code cleanup for memory_map_top_doown() |
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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).
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