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mm/memory: handle !page case in zap_present_pte() separately

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We don't need uptodate accessed/dirty bits, so in theory we could replace
ptep_get_and_clear_full() by an optimized ptep_clear_full() function. 
Let's rely on the provided pte.

Further, there is no scenario where we would have to insert uffd-wp
markers when zapping something that is not a normal page (i.e., zeropage).
Add a sanity check to make sure this remains true.

should_zap_folio() no longer has to handle NULL pointers.  This change
replaces 2/3 "!page/!folio" checks by a single "!page" one.

Note that arch_check_zapped_pte() on x86-64 checks the HW-dirty bit to
detect shadow stack entries.  But for shadow stack entries, the HW dirty
bit (in combination with non-writable PTEs) is set by software.  So for
the arch_check_zapped_pte() check, we don't have to sync against HW
setting the HW dirty bit concurrently, it is always set.

Link: https://lkml.kernel.org/r/20240214204435.167852-3-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2024-02-14 21:44:27 +01:00 committed by Andrew Morton
parent 789753e17c
commit 0cf18e839f
1 changed files with 11 additions and 11 deletions
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22
mm/memory.c
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@ -1499,10 +1499,6 @@ static inline bool should_zap_folio(struct zap_details *details,
if (should_zap_cows(details))
return true;
/* E.g. the caller passes NULL for the case of a zero folio */
if (!folio)
return true;
/* Otherwise we should only zap non-anon folios */
return !folio_test_anon(folio);
}
@ -1540,24 +1536,28 @@ static inline void zap_present_pte(struct mmu_gather *tlb,
int *rss, bool *force_flush, bool *force_break)
{
struct mm_struct *mm = tlb->mm;
struct folio *folio = NULL;
bool delay_rmap = false;
struct folio *folio;
struct page *page;
page = vm_normal_page(vma, addr, ptent);
if (page)
folio = page_folio(page);
if (!page) {
/* We don't need up-to-date accessed/dirty bits. */
ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm);
arch_check_zapped_pte(vma, ptent);
tlb_remove_tlb_entry(tlb, pte, addr);
VM_WARN_ON_ONCE(userfaultfd_wp(vma));
ksm_might_unmap_zero_page(mm, ptent);
return;
}
folio = page_folio(page);
if (unlikely(!should_zap_folio(details, folio)))
return;
ptent = ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm);
arch_check_zapped_pte(vma, ptent);
tlb_remove_tlb_entry(tlb, pte, addr);
zap_install_uffd_wp_if_needed(vma, addr, pte, details, ptent);
if (unlikely(!page)) {
ksm_might_unmap_zero_page(mm, ptent);
return;
}
if (!folio_test_anon(folio)) {
if (pte_dirty(ptent)) {