On 2/6/25 18:34, Ryan Roberts wrote:
> On 06/02/2025 06:46, Anshuman Khandual wrote:
>>
>>
>> On 2/5/25 20:39, Ryan Roberts wrote:
>>> commit c910f2b65518 ("arm64/mm: Update tlb invalidation routines for
>>> FEAT_LPA2") changed the "invalidation level unknown" hint from 0 to
>>> TLBI_TTL_UNKNOWN (INT_MAX). But the fallback "unknown level" path in
>>> flush_hugetlb_tlb_range() was not updated. So as it stands, when trying
>>> to invalidate CONT_PMD_SIZE or CONT_PTE_SIZE hugetlb mappings, we will
>>> spuriously try to invalidate at level 0 on LPA2-enabled systems.
>>>
>>> Fix this so that the fallback passes TLBI_TTL_UNKNOWN, and while we are
>>> at it, explicitly use the correct stride and level for CONT_PMD_SIZE and
>>> CONT_PTE_SIZE, which should provide a minor optimization.
>>>
>>> Cc: <stable@xxxxxxxxxxxxxxx>
>>> Fixes: c910f2b65518 ("arm64/mm: Update tlb invalidation routines for FEAT_LPA2")
>>> Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx>
>>> ---
>>> arch/arm64/include/asm/hugetlb.h | 20 ++++++++++++++------
>>> 1 file changed, 14 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/arch/arm64/include/asm/hugetlb.h b/arch/arm64/include/asm/hugetlb.h
>>> index 03db9cb21ace..8ab9542d2d22 100644
>>> --- a/arch/arm64/include/asm/hugetlb.h
>>> +++ b/arch/arm64/include/asm/hugetlb.h
>>> @@ -76,12 +76,20 @@ static inline void flush_hugetlb_tlb_range(struct vm_area_struct *vma,
>>> {
>>> unsigned long stride = huge_page_size(hstate_vma(vma));
>>>
>>> - if (stride == PMD_SIZE)
>>> - __flush_tlb_range(vma, start, end, stride, false, 2);
>>> - else if (stride == PUD_SIZE)
>>> - __flush_tlb_range(vma, start, end, stride, false, 1);
>>> - else
>>> - __flush_tlb_range(vma, start, end, PAGE_SIZE, false, 0);
>>> + switch (stride) {
>>> + case PUD_SIZE:
>>> + __flush_tlb_range(vma, start, end, PUD_SIZE, false, 1);
>>> + break;
>>
>> Just wondering - should not !__PAGETABLE_PMD_FOLDED and pud_sect_supported()
>> checks also be added here for this PUD_SIZE case ?
>
> Yeah I guess so. TBH, it's never been entirely clear to me what the benefit is?
> Is it just to remove (a tiny amount of) dead code when we know we don't support
> blocks at the level? Or is there something more fundamental going on that I've
> missed?
There is a generic fallback for PUD_SIZE in include/asm-generic/pgtable-nopud.h when
it is not defined on arm64 platform and pud_sect_supported() might also get optimized
by the compiler.
static inline bool pud_sect_supported(void)
{
return PAGE_SIZE == SZ_4K;
}
IIUC this just saves dead code from being compiled as you mentioned.
>
> We seem to be quite inconsistent with the use of pud_sect_supported() in
> hugetlbpage.c.
PUD_SIZE switch cases in hugetlb_mask_last_page() and arch_make_huge_pte() ? Those
should be fixed.
>
> Anyway, I'll add this in, I guess it's preferable to follow the established pattern.
Agreed.
>
> Thanks,
> Ryan
>
>>
>>> + case CONT_PMD_SIZE:
>>> + case PMD_SIZE:
>>> + __flush_tlb_range(vma, start, end, PMD_SIZE, false, 2);
>>> + break;
>>> + case CONT_PTE_SIZE:
>>> + __flush_tlb_range(vma, start, end, PAGE_SIZE, false, 3);
>>> + break;
>>> + default:
>>> + __flush_tlb_range(vma, start, end, PAGE_SIZE, false, TLBI_TTL_UNKNOWN);
>>> + }
>>> }
>>>
>>> #endif /* __ASM_HUGETLB_H */
>
