Paul Mackerras <pau...@ozlabs.org> writes: > On Wed, Nov 23, 2016 at 04:39:57PM +0530, Aneesh Kumar K.V wrote: >> When we are updating pte, we just need to flush the tlb mapping for >> that pte. Right now we do a full mm flush because we don't track page >> size. Update the interface to track the page size and use that to >> do the right tlb flush. > [...] > >> +int radix_get_mmu_psize(unsigned long page_size) >> +{ >> + int psize; >> + >> + if (page_size == (1UL << mmu_psize_defs[mmu_virtual_psize].shift)) >> + psize = mmu_virtual_psize; >> + else if (page_size == (1UL << mmu_psize_defs[MMU_PAGE_2M].shift)) >> + psize = MMU_PAGE_2M; >> + else if (page_size == (1UL << mmu_psize_defs[MMU_PAGE_1G].shift)) >> + psize = MMU_PAGE_1G; > > Do we actually have support for 1G pages yet? I couldn't see where > they get instantiated.
We use that for kernel linear mapping. > >> + else >> + return -1; >> + return psize; >> +} >> + >> + >> static int __init radix_dt_scan_page_sizes(unsigned long node, >> const char *uname, int depth, >> void *data) >> diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c >> index 911fdfb63ec1..503ae9bd3efe 100644 >> --- a/arch/powerpc/mm/pgtable.c >> +++ b/arch/powerpc/mm/pgtable.c >> @@ -219,12 +219,18 @@ int ptep_set_access_flags(struct vm_area_struct *vma, >> unsigned long address, >> pte_t *ptep, pte_t entry, int dirty) >> { >> int changed; >> + unsigned long page_size; >> + >> entry = set_access_flags_filter(entry, vma, dirty); >> changed = !pte_same(*(ptep), entry); >> if (changed) { >> - if (!is_vm_hugetlb_page(vma)) >> + if (!is_vm_hugetlb_page(vma)) { >> + page_size = PAGE_SIZE; >> assert_pte_locked(vma->vm_mm, address); >> - __ptep_set_access_flags(vma->vm_mm, ptep, entry); >> + } else >> + page_size = huge_page_size(hstate_vma(vma)); > > I don't understand how this can work with THP. You're determining the > page size using only the VMA, but with a THP VMA surely we get > different page sizes at different addresses? That applies only for hugetlb pages. Ie, for hugetlb vma we use vm_area_struct to determine the hugepage size. For THP hugepage configuration we end up calling int pmdp_set_access_flags(struct vm_area_struct *vma, unsigned long address, pmd_t *pmdp, pmd_t entry, int dirty) and for that we do __ptep_set_access_flags(vma->vm_mm, pmdp_ptep(pmdp), pmd_pte(entry), address, HPAGE_PMD_SIZE); > > More generally, I'm OK with adding the address parameter to > __ptep_set_access_flags, but I think Ben's suggestion of encoding the > page size in the PTE value is a good one. I think it is as simple as > the patch below (assuming we only support 2MB large pages for now). > That would simplify things a bit and also it would mean that we are > sure we know the page size correctly even with THP. > > diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h > b/arch/powerpc/include/asm/book3s/64/pgtable.h > index 9fd77f8..e4f3581 100644 > --- a/arch/powerpc/include/asm/book3s/64/pgtable.h > +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h > @@ -32,7 +32,8 @@ > #define _PAGE_SOFT_DIRTY 0x00000 > #endif > #define _PAGE_SPECIAL _RPAGE_SW2 /* software: special page */ > - > +#define _PAGE_GIGANTIC _RPAGE_SW0 /* software: 1GB page */ > +#define _PAGE_LARGE _RPAGE_SW1 /* software: 2MB page */ I already use _RPAGE_SW1 for _PAGE_DEVMAP (pmem/nvdimm, patch set to the list but not merged yet). We are really low on software free bits w.r.t pte and I was avoiding using that. I was thinking this series is a simpler cleanup of different page table update interface to take page size as argument. > > #define _PAGE_PTE (1ul << 62) /* distinguishes PTEs from > pointers */ > #define _PAGE_PRESENT (1ul << 63) /* pte contains a > translation */ > diff --git a/arch/powerpc/mm/pgtable-book3s64.c > b/arch/powerpc/mm/pgtable-book3s64.c > index f4f437c..7ff0289 100644 > --- a/arch/powerpc/mm/pgtable-book3s64.c > +++ b/arch/powerpc/mm/pgtable-book3s64.c > @@ -86,7 +86,7 @@ pmd_t pfn_pmd(unsigned long pfn, pgprot_t pgprot) > { > unsigned long pmdv; > > - pmdv = (pfn << PAGE_SHIFT) & PTE_RPN_MASK; > + pmdv = ((pfn << PAGE_SHIFT) & PTE_RPN_MASK) | _PAGE_LARGE; > return pmd_set_protbits(__pmd(pmdv), pgprot); > } > I will look at this and see if can make the patch simpler. But do we really want to use the pte bit for this ? Aren't we low on free pte bits ? -aneesh