Peter Zijlstra <[email protected]> writes: > On Thu, Oct 01, 2020 at 06:57:46AM -0700, [email protected] wrote: >> +/* >> + * Return the MMU page size of a given virtual address >> + */ >> +static u64 __perf_get_page_size(struct mm_struct *mm, unsigned long addr) >> +{ >> + pgd_t *pgd; >> + p4d_t *p4d; >> + pud_t *pud; >> + pmd_t *pmd; >> + pte_t *pte; >> + >> + pgd = pgd_offset(mm, addr); >> + if (pgd_none(*pgd)) >> + return 0; >> + >> + p4d = p4d_offset(pgd, addr); >> + if (!p4d_present(*p4d)) >> + return 0; >> + >> + if (p4d_leaf(*p4d)) >> + return 1ULL << P4D_SHIFT; >> + >> + pud = pud_offset(p4d, addr); >> + if (!pud_present(*pud)) >> + return 0; >> + >> + if (pud_leaf(*pud)) >> + return 1ULL << PUD_SHIFT; >> + >> + pmd = pmd_offset(pud, addr); >> + if (!pmd_present(*pmd)) >> + return 0; >> + >> + if (pmd_leaf(*pmd)) >> + return 1ULL << PMD_SHIFT; >> + >> + pte = pte_offset_map(pmd, addr); >> + if (!pte_present(*pte)) { >> + pte_unmap(pte); >> + return 0; >> + } >> + >> + pte_unmap(pte); >> + return PAGE_SIZE; >> +} > > So this mostly works, but gets a number of hugetlb and arch specific > things wrong. > > With the first 3 patches, this is only exposed to x86 and Power. > Michael, does the above work for you?
It might work on our server CPUs (book3s) but in general no I don't think it will work for all powerpc. > Looking at: > > arch/powerpc/include/asm/book3s/64/hugetlb.h:check_and_get_huge_psize() > > You seem to limit yourself to page-table sizes, however if I then look > at the same function in: > > arch/powerpc/include/asm/nohash/32/hugetlb-8xx.h > arch/powerpc/include/asm/nohash/hugetlb-book3e.h > > it doesn't seem to constrain itself so. Yeah the embedded CPUs have more weird sizes. I think we have all the logic in our __find_linux_pte(). > Patch 4 makes it all far worse by exposing it to pretty much everybody. > > Now, I think we can fix at least the user mappings with the below delta, > but if archs are using non-page-table MMU sizes we'll need arch helpers. > > ARM64 is in that last boat. I think we probably need it to be weak so we can provide our own version. cheers
