Messages in this thread | | | Date | Thu, 27 Mar 2008 19:13:20 -0700 | From | Jeremy Fitzhardinge <> | Subject | Re: [PATCH 2 of 4] hotplug-memory: adding non-section-aligned memory is bad |
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KAMEZAWA Hiroyuki wrote: > On Fri, 28 Mar 2008 10:34:51 +0900 > Yasunori Goto <y-goto@jp.fujitsu.com> wrote: > >>>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >>>> --- a/mm/memory_hotplug.c >>>> +++ b/mm/memory_hotplug.c >>>> @@ -300,6 +300,11 @@ >>>> int ret; >>>> u64 start = res->start; >>>> u64 size = res->end - res->start + 1; >>>> + >>>> + /* Adding non-section-aligned memory will give unexpected >>>> + and unintuitive results. */ >>>> + WARN_ON((start & SECTION_SIZE_MASK) != 0); >>>> + WARN_ON((size & SECTION_SIZE_MASK) != 0); >>>> >>>> >>> Why just WARNING ? not BUG_ON? >>> >> Both Nack. >> >> Because, firmware may occupy some area in the section. >> Firmware must exclude those area to notify kernel. So, E820, EFI, >> or _CRS of ACPI may return not aligned address and size. >> register_memory_resource() and walk_memory_resource() are to skip >> them silently. This is intended. >> >> > Ah, ok. sorry. > > Jeremy, I think you can check whether you have 'struct page' or not by > pfn_valid(). > > If pfn_valid() == false, you should call add_memory() and create > a section/mem_map. If pfn_valid() == true, you should just remove > PG_reserved bit in mem_map by online_page().
OK. Would that ever be necessary if I explicitly align my start and size?
J
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