On Fri, Oct 09, 2020 at 11:09:27AM +0200, Peter Zijlstra wrote: > 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? > > 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. > > 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. > > Will, can you live with the below, if not, what would you like to do, > make the entire function __weak so that you can override it, or hook > into it somewhere?
Hmm, so I don't think we currently have any PMUs that set 'data->addr' on arm64, in which case maybe none of this currently matters for us. However, I must admit that I couldn't figure out exactly what gets exposed to userspace when the backend drivers don't look at the sample_type or do anything with the addr field. Will
