On Sun, Mar 7, 2021 at 8:09 AM Greg Gallagher <g...@embeddedgreg.com> wrote:
>
>
> On Sun, Mar 7, 2021 at 7:56 AM Jan Kiszka <jan.kis...@siemens.com> wrote:
>
>> On 06.03.21 15:58, Philippe Gerum wrote:
>> >
>> > Jan Kiszka <jan.kis...@siemens.com> writes:
>> >
>> >> On 05.03.21 12:38, Jan Kiszka via Xenomai wrote:
>> >>> From: Jan Kiszka <jan.kis...@siemens.com>
>> >>>
>> >>> This is still needed to avoid that a real-time parent seems minor
>> faults
>> >>> after forking for shared pages until they are finally unshared.
>> >>>
>> >>> This missing support became visible in Xenomai when running the
>> complete
>> >>> smokey test suite on certain architectures/config combinations.
>> >>>
>> >>> Fixes: 0f0b6099c45f ("ipipe: mm: Drop un-COW from copy_pte_range")
>> >>> Signed-off-by: Jan Kiszka <jan.kis...@siemens.com>
>> >>> ---
>> >>>
>> >>> For discussion. If there is a better pattern in reach, I'm happy to
>> go
>> >>> that path as well.
>> >>>
>> >>> Otherwise, this should go into our 4.19 branches (Greg, your arm64
>> isn't
>> >>> in sync with noarch, you will need manual merging). Possibly, it
>> already
>> >>> applies to 5.4 as well, didn't check yet.
>> >>>
>> >>> mm/memory.c | 76
>> ++++++++++++++++++++++++++++++++++++++++++++++++-----
>> >>> 1 file changed, 69 insertions(+), 7 deletions(-)
>> >>>
>> >>> diff --git a/mm/memory.c b/mm/memory.c
>> >>> index 4cc7c72a0b7e..f102f4de2213 100644
>> >>> --- a/mm/memory.c
>> >>> +++ b/mm/memory.c
>> >>> @@ -141,6 +141,9 @@ EXPORT_SYMBOL(zero_pfn);
>> >>>
>> >>> unsigned long highest_memmap_pfn __read_mostly;
>> >>>
>> >>> +static bool cow_user_page(struct page *dst, struct page *src,
>> >>> + struct vm_fault *vmf);
>> >>> +
>> >>> /*
>> >>> * CONFIG_MMU architectures set up ZERO_PAGE in their paging_init()
>> >>> */
>> >>> @@ -957,8 +960,9 @@ struct page *vm_normal_page_pmd(struct
>> vm_area_struct *vma, unsigned long addr,
>> >>>
>> >>> static inline unsigned long
>> >>> copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
>> >>> - pte_t *dst_pte, pte_t *src_pte, struct vm_area_struct
>> *vma,
>> >>> - unsigned long addr, int *rss)
>> >>> + pte_t *dst_pte, pte_t *src_pte, struct vm_area_struct *vma,
>> >>> + unsigned long addr, int *rss, pmd_t *src_pmd,
>> >>> + struct page *uncow_page)
>> >>> {
>> >>> unsigned long vm_flags = vma->vm_flags;
>> >>> pte_t pte = *src_pte;
>> >>> @@ -1036,6 +1040,33 @@ copy_one_pte(struct mm_struct *dst_mm, struct
>> mm_struct *src_mm,
>> >>> * in the parent and the child
>> >>> */
>> >>> if (is_cow_mapping(vm_flags) && pte_write(pte)) {
>> >>> +#ifdef CONFIG_IPIPE
>> >>> + if (uncow_page) {
>> >>> + struct page *old_page = vm_normal_page(vma, addr,
>> pte);
>> >>> + struct vm_fault vmf;
>> >>> +
>> >>> + vmf.vma = vma;
>> >>> + vmf.address = addr;
>> >>> + vmf.orig_pte = pte;
>> >>> + vmf.pmd = src_pmd;
>> >>> +
>> >>> + if (cow_user_page(uncow_page, old_page, &vmf)) {
>> >>> + pte = mk_pte(uncow_page,
>> vma->vm_page_prot);
>> >>> +
>> >>> + if (vm_flags & VM_SHARED)
>> >>> + pte = pte_mkclean(pte);
>> >>> + pte = pte_mkold(pte);
>> >>> +
>> >>> + page_add_new_anon_rmap(uncow_page, vma,
>> addr,
>> >
>> >>> + false);
>> >>> + rss[!!PageAnon(uncow_page)]++;
>> >>> + goto out_set_pte;
>> >>> + } else {
>> >>> + /* unexpected: source page no longer
>> present */
>> >>> + WARN_ON_ONCE(1);
>> >>> + }
>> >>> + }
>> >>> +#endif /* CONFIG_IPIPE */
>> >>> ptep_set_wrprotect(src_mm, addr, src_pte);
>> >>> pte = pte_wrprotect(pte);
>> >>> }
>> >>> @@ -1083,13 +1114,27 @@ static int copy_pte_range(struct mm_struct
>> *dst_mm, struct mm_struct *src_mm,
>> >>> int progress = 0;
>> >>> int rss[NR_MM_COUNTERS];
>> >>> swp_entry_t entry = (swp_entry_t){0};
>> >>> -
>> >>> + struct page *uncow_page = NULL;
>> >>> +#ifdef CONFIG_IPIPE
>> >>> + int do_cow_break = 0;
>> >>> +again:
>> >>> + if (do_cow_break) {
>> >>> + uncow_page = alloc_page_vma(GFP_HIGHUSER, vma, addr);
>> >>> + if (uncow_page == NULL)
>> >>> + return -ENOMEM;
>> >>> + do_cow_break = 0;
>> >>> + }
>> >>> +#else
>> >>> again:
>> >>> +#endif
>> >>> init_rss_vec(rss);
>> >>>
>> >>> dst_pte = pte_alloc_map_lock(dst_mm, dst_pmd, addr, &dst_ptl);
>> >>> - if (!dst_pte)
>> >>> + if (!dst_pte) {
>> >>> + if (uncow_page)
>> >>> + put_page(uncow_page);
>> >>> return -ENOMEM;
>> >>> + }
>> >>> src_pte = pte_offset_map(src_pmd, addr);
>> >>> src_ptl = pte_lockptr(src_mm, src_pmd);
>> >>> spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
>> >>> @@ -1112,8 +1157,25 @@ static int copy_pte_range(struct mm_struct
>> *dst_mm, struct mm_struct *src_mm,
>> >>> progress++;
>> >>> continue;
>> >>> }
>> >>> +#ifdef CONFIG_IPIPE
>> >>> + if (likely(uncow_page == NULL) &&
>> likely(pte_present(*src_pte))) {
>> >>> + if (is_cow_mapping(vma->vm_flags) &&
>> >>> + test_bit(MMF_VM_PINNED, &src_mm->flags) &&
>> >>> + ((vma->vm_flags|src_mm->def_flags) &
>> VM_LOCKED)) {
>> >>> + arch_leave_lazy_mmu_mode();
>> >>> + spin_unlock(src_ptl);
>> >>> + pte_unmap(src_pte);
>> >>> + add_mm_rss_vec(dst_mm, rss);
>> >>> + pte_unmap_unlock(dst_pte, dst_ptl);
>> >>> + cond_resched();
>> >>> + do_cow_break = 1;
>> >>> + goto again;
>> >>> + }
>> >>> + }
>> >>> +#endif
>> >>> entry.val = copy_one_pte(dst_mm, src_mm, dst_pte, src_pte,
>> >>> - vma, addr, rss);
>> >>> + vma, addr, rss, src_pmd,
>> uncow_page);
>> >>> + uncow_page = NULL;
>> >>> if (entry.val)
>> >>> break;
>> >>> progress += 8;
>> >>> @@ -2348,8 +2410,8 @@ static inline int pte_unmap_same(struct
>> mm_struct *mm, pmd_t *pmd,
>> >>> return same;
>> >>> }
>> >>>
>> >>> -static inline bool cow_user_page(struct page *dst, struct page *src,
>> >>> - struct vm_fault *vmf)
>> >>> +static bool cow_user_page(struct page *dst, struct page *src,
>> >>> + struct vm_fault *vmf)
>> >>> {
>> >>> bool ret;
>> >>> void *kaddr;
>> >>>
>> >>
>> >> With this applied to ipipe-4.19 and 5.4 queues, related issues are
>> gone, see
>> >>
>> >> https://source.denx.de/Xenomai/xenomai-images/-/pipelines/6670
>> >>
>> >> I'm inclined to take this for now so that we can move forward with
>> other
>> >> topics. Any comments?
>> >>
>> >
>> > Fine with me. This code can be simplified, working on it. I'll channel
>> > this through Dovetail.
>> >
>>
>> OK, applied.
>>
>> Greg, you can find updated no-arch branches for 4.19 and 5.4.
>
>
>> Did this commit go into the no-arch tree? I'll have new arm/arm64 5.4 and
4.19 releases this week (aiming for Wednesday).
Thanks
Greg
