Commit 4369deaa authored by Dan Williams's avatar Dan Williams Committed by Ingo Molnar

generic/pgtable: Introduce set_pte_safe()

Commit:

  f77084d9 "x86/mm/pat: Disable preemption around __flush_tlb_all()"

introduced a warning to capture cases __flush_tlb_all() is called without
pre-emption disabled. It triggers a false positive warning in the memory
hotplug path.

On investigation it was found that the __flush_tlb_all() calls are not
necessary. However, they are only "not necessary" in practice provided
the ptes are being initially populated from the !present state.

Introduce set_pte_safe() as a sanity check that the pte is being updated
in a way that does not require a TLB flush.

Forgive the macro, the availability of the various of set_pte() levels
is hit and miss across architectures.

[ mingo: Minor readability edits. ]
Suggested-by: default avatarPeter Zijlstra <peterz@infradead.org>
Suggested-by: default avatarDave Hansen <dave.hansen@intel.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/279dadae-9148-465c-7ec6-3f37e026c6c9@intel.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 0cebbb60
......@@ -400,6 +400,44 @@ static inline int pgd_same(pgd_t pgd_a, pgd_t pgd_b)
}
#endif
/*
* Use set_p*_safe(), and elide TLB flushing, when confident that *no*
* TLB flush will be required as a result of the "set". For example, use
* in scenarios where it is known ahead of time that the routine is
* setting non-present entries, or re-setting an existing entry to the
* same value. Otherwise, use the typical "set" helpers and flush the
* TLB.
*/
#define set_pte_safe(ptep, pte) \
({ \
WARN_ON_ONCE(pte_present(*ptep) && !pte_same(*ptep, pte)); \
set_pte(ptep, pte); \
})
#define set_pmd_safe(pmdp, pmd) \
({ \
WARN_ON_ONCE(pmd_present(*pmdp) && !pmd_same(*pmdp, pmd)); \
set_pmd(pmdp, pmd); \
})
#define set_pud_safe(pudp, pud) \
({ \
WARN_ON_ONCE(pud_present(*pudp) && !pud_same(*pudp, pud)); \
set_pud(pudp, pud); \
})
#define set_p4d_safe(p4dp, p4d) \
({ \
WARN_ON_ONCE(p4d_present(*p4dp) && !p4d_same(*p4dp, p4d)); \
set_p4d(p4dp, p4d); \
})
#define set_pgd_safe(pgdp, pgd) \
({ \
WARN_ON_ONCE(pgd_present(*pgdp) && !pgd_same(*pgdp, pgd)); \
set_pgd(pgdp, pgd); \
})
#ifndef __HAVE_ARCH_DO_SWAP_PAGE
/*
* Some architectures support metadata associated with a page. When a
......
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