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SubjectRe: [Bug fix PATCH 1/2] acpi, movablemem_map: Exclude memblock.reserved ranges when parsing SRAT.
On 02/20/2013 08:31 PM, Tang Chen wrote:
> On 02/20/2013 07:00 PM, Tang Chen wrote:
>> As mentioned by HPA before, when we are using movablemem_map=acpi, if
>> all the
>> memory ranges in SRAT is hotpluggable, then no memory can be used by
>> kernel.
>>
>> Before parsing SRAT, memblock has already reserve some memory ranges
>> for other
>> purposes, such as for kernel image, and so on. We cannot prevent
>> kernel from
>> using these memory. So we need to exclude these ranges even if these
>> memory is
>> hotpluggable.
>>
>> This patch changes the movablemem_map=acpi option's behavior. The
>> memory ranges
>> reserved by memblock will not be added into movablemem_map.map[]. So
>> even if
>> all the memory is hotpluggable, there will always be memory that
>> could be used
>> by the kernel.
>>

What's the relationship between e820 map and SRAT?

>> Reported-by: H Peter Anvin<hpa@zytor.com>
>> Signed-off-by: Tang Chen<tangchen@cn.fujitsu.com>
>> ---
>> arch/x86/mm/srat.c | 18 +++++++++++++++++-
>> 1 files changed, 17 insertions(+), 1 deletions(-)
>>
>> diff --git a/arch/x86/mm/srat.c b/arch/x86/mm/srat.c
>> index 62ba97b..b8028b2 100644
>> --- a/arch/x86/mm/srat.c
>> +++ b/arch/x86/mm/srat.c
>> @@ -145,7 +145,7 @@ static inline int save_add_info(void) {return 0;}
>> static void __init
>> handle_movablemem(int node, u64 start, u64 end, u32 hotpluggable)
>> {
>> - int overlap;
>> + int overlap, i;
>> unsigned long start_pfn, end_pfn;
>>
>> start_pfn = PFN_DOWN(start);
>> @@ -161,8 +161,24 @@ handle_movablemem(int node, u64 start, u64 end,
>> u32 hotpluggable)
>> *
>> * Using movablemem_map, we can prevent memblock from
>> allocating memory
>> * on ZONE_MOVABLE at boot time.
>> + *
>> + * Before parsing SRAT, memblock has already reserve some memory
>> ranges
>> + * for other purposes, such as for kernel image. We cannot prevent
>> + * kernel from using these memory, so we need to exclude these
>> memory
>> + * even if it is hotpluggable.
>> */
>> if (hotpluggable&& movablemem_map.acpi) {
>> + /* Exclude ranges reserved by memblock. */
>> + struct memblock_type *rgn =&memblock.reserved;
>> +
>> + for (i = 0; i< rgn->cnt; i++) {
>> + if (end<= rgn->regions[i].base ||
>> + start>= rgn->regions[i].base +
>> + rgn->regions[i].size)
>
> Hi all,
>
> Here, I scan the memblock.reserved each time we parse an entry because
> the
> rgn->regions[i].nid is set to MAX_NUMNODES in memblock_reserve(). So I
> cannot
> obtain the nid which the kernel resides in directly from
> memblock.reserved.
>
> I think there could be some problems if the memory ranges in SRAT are
> not in
> increasing order, since if [3,4) [1,2) are all on node0, and kernel is
> not
> using [3,4), but using [1,2), then I cannot remove [3,4) because I
> don't know
> on which node [3,4) is.
>
> Any idea for this ?
>
> And by the way, I think this approach works well when the memory
> entries in
> SRAT are arranged in increasing order.
>
> Thanks. :)
>
>> + continue;
>> + goto out;
>> + }
>> +
>> insert_movablemem_map(start_pfn, end_pfn);
>>
>> /*
>
> --
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