Vineet Gupta <Vineet.Gupta1@xxxxxxxxxxxx> writes: > This showed up on ARC when running LMBench bw_mem tests as > Overlapping TLB Machine Check Exception triggered due to STLB entry > (2M pages) overlapping some NTLB entry (regular 8K page). > > bw_mem 2m touches a large chunk of vaddr creating NTLB entries. > In the interim khugepaged kicks in, collapsing the contiguous ptes into > a single pmd. pmdp_collapse_flush()->flush_pmd_tlb_range() is called to > flush out NTLB entries for the ptes. This for ARC (by design) can only > shootdown STLB entries (for pmd). The stray NTLB entries cause the overlap > with the subsequent STLB entry for collapsed page. > So make pmdp_collapse_flush() call pte flush interface not pmd flush. > > Note that originally all thp flush call sites in generic code called > flush_tlb_range() leaving it to architecture to implement the flush for > pte and/or pmd. Commit 12ebc1581ad11454 changed this by calling a new > opt-in API flush_pmd_tlb_range() which made the semantics more explicit > but failed to distinguish the pte vs pmd flush in generic code, which is > what this patch fixes. > > Note that ARC can fixed w/o touching the generic pmdp_collapse_flush() > by defining a ARC version, but that defeats the purpose of generic > version, plus sementically this is the right thing to do. > > Fixes STAR 9000961194: LMBench on AXS103 triggering duplicate TLB > exceptions with super pages > > Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx> > Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> #4.4 > Cc: <linux-snps-arc@xxxxxxxxxxxxxxxxxxx> > Cc: linux-kernel@xxxxxxxxxxxxxxx > Cc: linux-mm@xxxxxxxxx > Fixes: 12ebc1581ad11454 ("mm,thp: introduce flush_pmd_tlb_range") > Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx> We do have reverse usage in migration code path, which I have as a patch here. https://github.com/kvaneesh/linux/commit/b8a78933fea93cb0b2978868e59a0a4b12eb92eb > --- > mm/pgtable-generic.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c > index 7d3db0247983..1ba58213ad65 100644 > --- a/mm/pgtable-generic.c > +++ b/mm/pgtable-generic.c > @@ -210,7 +210,9 @@ pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address, > VM_BUG_ON(address & ~HPAGE_PMD_MASK); > VM_BUG_ON(pmd_trans_huge(*pmdp)); > pmd = pmdp_huge_get_and_clear(vma->vm_mm, address, pmdp); > - flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE); > + > + /* collapse entails shooting down ptes not pmd */ > + flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE); > return pmd; > } > #endif > -- > 2.5.0 -aneesh -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html