On 12/21/24 00:05, Catalin Marinas wrote:
> On Mon, Dec 09, 2024 at 05:42:27PM +0800, Zhenhua Huang wrote:
>> vmemmap_check_pmd() is used to determine if needs to populate to base
>> pages. Implement it for arm64 arch.
>>
>> Fixes: 2045a3b8911b ("mm/sparse-vmemmap: generalise vmemmap_populate_hugepages()")
>> Signed-off-by: Zhenhua Huang <quic_zhenhuah@xxxxxxxxxxx>
>> ---
>> arch/arm64/mm/mmu.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>> index fd59ee44960e..41c7978a92be 100644
>> --- a/arch/arm64/mm/mmu.c
>> +++ b/arch/arm64/mm/mmu.c
>> @@ -1169,7 +1169,8 @@ int __meminit vmemmap_check_pmd(pmd_t *pmdp, int node,
>> unsigned long addr, unsigned long next)
>> {
>> vmemmap_verify((pte_t *)pmdp, node, addr, next);
>> - return 1;
>> +
>> + return pmd_sect(*pmdp);
Please change this as pmd_sect(READ_ONCE(*pmdp)) instead.
>> }
>>
>> int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
>
> Don't we need this patch only if we implement the first one? Please fold
> it into the other patch.
Seems like these patches might not be related.
While creating huge page based vmemmap mapping during vmemmap_populate_hugepages(),
vmemmap_check_pmd() validates if a populated (i.e pmd_none) PMD already represents
a huge mapping and can be skipped there after.
Current implementation for vmemmap_check_pmd() on arm64, unconditionally returns 1
thus asserting that the given populated PMD entry is a huge one indeed, which will
be the case unless something is wrong. vmemmap_verify() only ensures that the node
where the pfn is allocated from is local.
int __meminit vmemmap_check_pmd(pmd_t *pmdp, int node,
unsigned long addr, unsigned long next)
{
vmemmap_verify((pte_t *)pmdp, node, addr, next);
return 1;
}
However it does not really check the entry to be a section mapping which it should.
Returning pmd_sect(READ_ONCE(*pmdp)) is the right thing, which should have been the
case from the beginning when vmemmap_check_pmd() was added. I guess because arm64's
original vmemmap_populate() checked only for vmemmap_verify() as well. So probably
this does not need a "Fixes: " tag.
