Messages in this thread Patch in this message | | | From | "Kirill A. Shutemov" <> | Subject | [PATCHv14 08/17] x86/mm: Reduce untagged_addr() overhead until the first LAM user | Date | Wed, 11 Jan 2023 15:37:27 +0300 |
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Use static key to reduce untagged_addr() overhead.
The key only gets enabled when the first process enables LAM.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> --- arch/x86/include/asm/uaccess.h | 8 ++++++-- arch/x86/kernel/process_64.c | 4 ++++ 2 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index 32c9dd052e43..f9f85d596581 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -24,6 +24,8 @@ static inline bool pagefault_disabled(void); #endif #ifdef CONFIG_ADDRESS_MASKING +DECLARE_STATIC_KEY_FALSE(tagged_addr_key); + /* * Mask out tag bits from the address. * @@ -32,8 +34,10 @@ static inline bool pagefault_disabled(void); */ #define __untagged_addr(untag_mask, addr) ({ \ u64 __addr = (__force u64)(addr); \ - s64 sign = (s64)__addr >> 63; \ - __addr &= untag_mask | sign; \ + if (static_branch_likely(&tagged_addr_key)) { \ + s64 sign = (s64)__addr >> 63; \ + __addr &= untag_mask | sign; \ + } \ (__force __typeof__(addr))__addr; \ }) diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 88aae519c8f8..1b41c60ebf6e 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -745,6 +745,9 @@ static long prctl_map_vdso(const struct vdso_image *image, unsigned long addr) #ifdef CONFIG_ADDRESS_MASKING +DEFINE_STATIC_KEY_FALSE(tagged_addr_key); +EXPORT_SYMBOL_GPL(tagged_addr_key); + #define LAM_U57_BITS 6 static int prctl_enable_tagged_addr(struct mm_struct *mm, unsigned long nr_bits) @@ -781,6 +784,7 @@ static int prctl_enable_tagged_addr(struct mm_struct *mm, unsigned long nr_bits) mmap_write_unlock(mm); + static_branch_enable(&tagged_addr_key); return 0; } #endif -- 2.38.2
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