On 2024-01-03 9:02 AM, Jisheng Zhang wrote:
> On Tue, Jan 02, 2024 at 02:00:49PM -0800, Samuel Holland wrote:
>> Even if multiple ASIDs are not supported, using the single-ASID variant
>> of the sfence.vma instruction preserves TLB entries for global (kernel)
>> pages. So it is always more efficient to use the single-ASID code path.
>>
>> Signed-off-by: Samuel Holland <samuel.holland@xxxxxxxxxx>
>> ---
>>
>> Changes in v4:
>> - There is now only one copy of __flush_tlb_range()
>>
>> Changes in v2:
>> - Update both copies of __flush_tlb_range()
>>
>> arch/riscv/include/asm/mmu_context.h | 2 --
>> arch/riscv/mm/context.c | 3 +--
>> arch/riscv/mm/tlbflush.c | 3 +--
>> 3 files changed, 2 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/riscv/include/asm/mmu_context.h b/arch/riscv/include/asm/mmu_context.h
>> index 7030837adc1a..b0659413a080 100644
>> --- a/arch/riscv/include/asm/mmu_context.h
>> +++ b/arch/riscv/include/asm/mmu_context.h
>> @@ -33,8 +33,6 @@ static inline int init_new_context(struct task_struct *tsk,
>> return 0;
>> }
>>
>> -DECLARE_STATIC_KEY_FALSE(use_asid_allocator);
>> -
>> #include <asm-generic/mmu_context.h>
>>
>> #endif /* _ASM_RISCV_MMU_CONTEXT_H */
>> diff --git a/arch/riscv/mm/context.c b/arch/riscv/mm/context.c
>> index 3ca9b653df7d..20057085ab8a 100644
>> --- a/arch/riscv/mm/context.c
>> +++ b/arch/riscv/mm/context.c
>> @@ -18,8 +18,7 @@
>>
>> #ifdef CONFIG_MMU
>>
>> -DEFINE_STATIC_KEY_FALSE(use_asid_allocator);
>> -
>> +static DEFINE_STATIC_KEY_FALSE(use_asid_allocator);
>
> One of my optimization "riscv: tlb: avoid tlb flushing if fullmm == 1"
> will make use of use_asid_allocator, so could we remove this modification?
Yes, I can leave the global declaration alone for now.
>> static unsigned long num_asids;
>>
>> static atomic_long_t current_version;
>> diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
>> index 5ec621545c69..39d80f56d292 100644
>> --- a/arch/riscv/mm/tlbflush.c
>> +++ b/arch/riscv/mm/tlbflush.c
>> @@ -84,8 +84,7 @@ static void __flush_tlb_range(struct mm_struct *mm, unsigned long start,
>> if (cpumask_empty(cmask))
>> return;
>>
>> - if (static_branch_unlikely(&use_asid_allocator))
>> - asid = cntx2asid(atomic_long_read(&mm->context.id));
>> + asid = cntx2asid(atomic_long_read(&mm->context.id));
>> } else {
>> cmask = cpu_online_mask;
>> }
>> --
>> 2.42.0
>>
>>
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