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Subject[RFC PATCH 16/26] hugetlb: make hugetlb_change_protection compatible with HGM
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HugeTLB is now able to change the protection of hugepages that are
mapped at high granularity.

I need to add more of the HugeTLB PTE wrapper functions to clean up this
patch. I'll do this in the next version.

Signed-off-by: James Houghton <jthoughton@google.com>
---
mm/hugetlb.c | 91 +++++++++++++++++++++++++++++++++++-----------------
1 file changed, 62 insertions(+), 29 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 51fc1d3f122f..f9c7daa6c090 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6476,14 +6476,15 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
{
struct mm_struct *mm = vma->vm_mm;
unsigned long start = address;
- pte_t *ptep;
pte_t pte;
struct hstate *h = hstate_vma(vma);
- unsigned long pages = 0, psize = huge_page_size(h);
+ unsigned long base_pages = 0, psize = huge_page_size(h);
bool shared_pmd = false;
struct mmu_notifier_range range;
bool uffd_wp = cp_flags & MM_CP_UFFD_WP;
bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE;
+ struct hugetlb_pte hpte;
+ bool hgm_enabled = hugetlb_hgm_enabled(vma);

/*
* In the case of shared PMDs, the area to flush could be beyond
@@ -6499,28 +6500,38 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,

mmu_notifier_invalidate_range_start(&range);
i_mmap_lock_write(vma->vm_file->f_mapping);
- for (; address < end; address += psize) {
+ while (address < end) {
spinlock_t *ptl;
- ptep = huge_pte_offset(mm, address, psize);
- if (!ptep)
+ pte_t *ptep = huge_pte_offset(mm, address, huge_page_size(h));
+
+ if (!ptep) {
+ address += huge_page_size(h);
continue;
- ptl = huge_pte_lock(h, mm, ptep);
- if (huge_pmd_unshare(mm, vma, &address, ptep)) {
+ }
+ hugetlb_pte_populate(&hpte, ptep, huge_page_shift(h));
+ if (hgm_enabled) {
+ int ret = hugetlb_walk_to(mm, &hpte, address, PAGE_SIZE,
+ /*stop_at_none=*/true);
+ BUG_ON(ret);
+ }
+
+ ptl = hugetlb_pte_lock(mm, &hpte);
+ if (huge_pmd_unshare(mm, vma, &address, hpte.ptep)) {
/*
* When uffd-wp is enabled on the vma, unshare
* shouldn't happen at all. Warn about it if it
* happened due to some reason.
*/
WARN_ON_ONCE(uffd_wp || uffd_wp_resolve);
- pages++;
+ base_pages += hugetlb_pte_size(&hpte) / PAGE_SIZE;
spin_unlock(ptl);
shared_pmd = true;
- continue;
+ goto next_hpte;
}
- pte = huge_ptep_get(ptep);
+ pte = hugetlb_ptep_get(&hpte);
if (unlikely(is_hugetlb_entry_hwpoisoned(pte))) {
spin_unlock(ptl);
- continue;
+ goto next_hpte;
}
if (unlikely(is_hugetlb_entry_migration(pte))) {
swp_entry_t entry = pte_to_swp_entry(pte);
@@ -6540,12 +6551,13 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
newpte = pte_swp_mkuffd_wp(newpte);
else if (uffd_wp_resolve)
newpte = pte_swp_clear_uffd_wp(newpte);
- set_huge_swap_pte_at(mm, address, ptep,
- newpte, psize);
- pages++;
+ set_huge_swap_pte_at(mm, address, hpte.ptep,
+ newpte,
+ hugetlb_pte_size(&hpte));
+ base_pages += hugetlb_pte_size(&hpte) / PAGE_SIZE;
}
spin_unlock(ptl);
- continue;
+ goto next_hpte;
}
if (unlikely(pte_marker_uffd_wp(pte))) {
/*
@@ -6553,21 +6565,40 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
* no need for huge_ptep_modify_prot_start/commit().
*/
if (uffd_wp_resolve)
- huge_pte_clear(mm, address, ptep, psize);
+ huge_pte_clear(mm, address, hpte.ptep, psize);
}
- if (!huge_pte_none(pte)) {
+ if (!hugetlb_pte_none(&hpte)) {
pte_t old_pte;
- unsigned int shift = huge_page_shift(hstate_vma(vma));
-
- old_pte = huge_ptep_modify_prot_start(vma, address, ptep);
- pte = huge_pte_modify(old_pte, newprot);
- pte = arch_make_huge_pte(pte, shift, vma->vm_flags);
- if (uffd_wp)
- pte = huge_pte_mkuffd_wp(huge_pte_wrprotect(pte));
- else if (uffd_wp_resolve)
- pte = huge_pte_clear_uffd_wp(pte);
- huge_ptep_modify_prot_commit(vma, address, ptep, old_pte, pte);
- pages++;
+ unsigned int shift = hpte.shift;
+ /*
+ * This is ugly. This will be cleaned up in a future
+ * version of this series.
+ */
+ if (shift > PAGE_SHIFT) {
+ old_pte = huge_ptep_modify_prot_start(
+ vma, address, hpte.ptep);
+ pte = huge_pte_modify(old_pte, newprot);
+ pte = arch_make_huge_pte(
+ pte, shift, vma->vm_flags);
+ if (uffd_wp)
+ pte = huge_pte_mkuffd_wp(huge_pte_wrprotect(pte));
+ else if (uffd_wp_resolve)
+ pte = huge_pte_clear_uffd_wp(pte);
+ huge_ptep_modify_prot_commit(
+ vma, address, hpte.ptep,
+ old_pte, pte);
+ } else {
+ old_pte = ptep_modify_prot_start(
+ vma, address, hpte.ptep);
+ pte = pte_modify(old_pte, newprot);
+ if (uffd_wp)
+ pte = pte_mkuffd_wp(pte_wrprotect(pte));
+ else if (uffd_wp_resolve)
+ pte = pte_clear_uffd_wp(pte);
+ ptep_modify_prot_commit(
+ vma, address, hpte.ptep, old_pte, pte);
+ }
+ base_pages += hugetlb_pte_size(&hpte) / PAGE_SIZE;
} else {
/* None pte */
if (unlikely(uffd_wp))
@@ -6576,6 +6607,8 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
make_pte_marker(PTE_MARKER_UFFD_WP));
}
spin_unlock(ptl);
+next_hpte:
+ address += hugetlb_pte_size(&hpte);
}
/*
* Must flush TLB before releasing i_mmap_rwsem: x86's huge_pmd_unshare
@@ -6597,7 +6630,7 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
i_mmap_unlock_write(vma->vm_file->f_mapping);
mmu_notifier_invalidate_range_end(&range);

- return pages << h->order;
+ return base_pages;
}

/* Return true if reservation was successful, false otherwise. */
--
2.37.0.rc0.161.g10f37bed90-goog
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