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author | Nadav Amit <namit@vmware.com> | 2022-05-09 18:20:50 -0700 |
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committer | Andrew Morton <akpm@linux-foundation.org> | 2022-05-13 07:20:05 -0700 |
commit | c9fe66560bf2dc7d109754414e309888cb8c9ba9 (patch) | |
tree | b609e89d09822a588f5445e736edc83e5b34af35 /include | |
parent | 4a18419f71cdf9155d2d2a6c79546f720978b990 (diff) | |
download | linux-stable-c9fe66560bf2dc7d109754414e309888cb8c9ba9.tar.gz linux-stable-c9fe66560bf2dc7d109754414e309888cb8c9ba9.tar.bz2 linux-stable-c9fe66560bf2dc7d109754414e309888cb8c9ba9.zip |
mm/mprotect: do not flush when not required architecturally
Currently, using mprotect() to unprotect a memory region or uffd to
unprotect a memory region causes a TLB flush. However, in such cases the
PTE is often not modified (i.e., remain RO) and therefore not TLB flush is
needed.
Add an arch-specific pte_needs_flush() which tells whether a TLB flush is
needed based on the old PTE and the new one. Implement an x86
pte_needs_flush().
Always flush the TLB when it is architecturally needed even when skipping
a TLB flush might only result in a spurious page-faults by skipping the
flush.
Even with such conservative manner, we can in the future further refine
the checks to test whether a PTE is present by only considering the
architectural _PAGE_PRESENT flag instead of {pte|pmd}_preesnt(). For not
be careful and use the latter.
Link: https://lkml.kernel.org/r/20220401180821.1986781-3-namit@vmware.com
Signed-off-by: Nadav Amit <namit@vmware.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Nick Piggin <npiggin@gmail.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r-- | include/asm-generic/tlb.h | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h index eee6f7763a39..ff3e82553a76 100644 --- a/include/asm-generic/tlb.h +++ b/include/asm-generic/tlb.h @@ -658,6 +658,20 @@ static inline void tlb_flush_p4d_range(struct mmu_gather *tlb, } while (0) #endif +#ifndef pte_needs_flush +static inline bool pte_needs_flush(pte_t oldpte, pte_t newpte) +{ + return true; +} +#endif + +#ifndef huge_pmd_needs_flush +static inline bool huge_pmd_needs_flush(pmd_t oldpmd, pmd_t newpmd) +{ + return true; +} +#endif + #endif /* CONFIG_MMU */ #endif /* _ASM_GENERIC__TLB_H */ |