Messages in this thread Patches in this message | | | From | Atish Patra <> | Subject | Re: [PATCH] RISC-V: Issue a local tlb flush if possible. | Date | Sat, 10 Aug 2019 09:21:45 +0000 |
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On 8/9/19, 6:43 PM, "Atish Patra" <Atish.Patra@wdc.com> wrote:
In RISC-V, tlb flush happens via SBI which is expensive. If the target cpumask contains a local hartid, some cost can be saved by issuing a local tlb flush as we do that in OpenSBI anyways.
Signed-off-by: Atish Patra <atish.patra@wdc.com> --- arch/riscv/include/asm/tlbflush.h | 33 +++++++++++++++++++++++++++---- 1 file changed, 29 insertions(+), 4 deletions(-) diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h index 687dd19735a7..b32ba4fa5888 100644 --- a/arch/riscv/include/asm/tlbflush.h +++ b/arch/riscv/include/asm/tlbflush.h @@ -8,6 +8,7 @@ #define _ASM_RISCV_TLBFLUSH_H #include <linux/mm_types.h> +#include <linux/sched.h> #include <asm/smp.h> /* @@ -46,14 +47,38 @@ static inline void remote_sfence_vma(struct cpumask *cmask, unsigned long start, unsigned long size) { struct cpumask hmask; + struct cpumask tmask; + int cpuid = smp_processor_id(); cpumask_clear(&hmask); - riscv_cpuid_to_hartid_mask(cmask, &hmask); - sbi_remote_sfence_vma(hmask.bits, start, size); + cpumask_clear(&tmask); + + if (cmask) + cpumask_copy(&tmask, cmask); + else + cpumask_copy(&tmask, cpu_online_mask); + + if (cpumask_test_cpu(cpuid, &tmask)) { + /* Save trap cost by issuing a local tlb flush here */ + if ((start == 0 && size == -1) || (size > PAGE_SIZE)) + local_flush_tlb_all(); + else if (size == PAGE_SIZE) + local_flush_tlb_page(start); + cpumask_clear_cpu(cpuid, &tmask); + } else if (cpumask_empty(&tmask)) { + /* cpumask is empty. So just do a local flush */ + local_flush_tlb_all(); + return; + } + + if (!cpumask_empty(&tmask)) { + riscv_cpuid_to_hartid_mask(&tmask, &hmask); + sbi_remote_sfence_vma(hmask.bits, start, size); + } } -#define flush_tlb_all() sbi_remote_sfence_vma(NULL, 0, -1) -#define flush_tlb_page(vma, addr) flush_tlb_range(vma, addr, 0) +#define flush_tlb_all() remote_sfence_vma(NULL, 0, -1) +#define flush_tlb_page(vma, addr) flush_tlb_range(vma, addr, (addr) + PAGE_SIZE)
I did not see Paul's patch to fix this. I will remove this in v2 and rebase on top of Paul's patch.
Regards, Atish #define flush_tlb_range(vma, start, end) \ remote_sfence_vma(mm_cpumask((vma)->vm_mm), start, (end) - (start)) #define flush_tlb_mm(mm) \ -- 2.21.0
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