On Tue, Jan 02, 2024 at 02:00:41PM -0800, Samuel Holland wrote:
> If no other CPU is online, a local cache or TLB flush is sufficient.
> These checks can be constant-folded when SMP is disabled.
>
> Signed-off-by: Samuel Holland <samuel.holland@xxxxxxxxxx>
> ---
>
> Changes in v4:
> - New patch for v4
>
> arch/riscv/mm/cacheflush.c | 4 +++-
> arch/riscv/mm/tlbflush.c | 4 +++-
> 2 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c
> index 47c485bc7df0..f7933ae88a55 100644
> --- a/arch/riscv/mm/cacheflush.c
> +++ b/arch/riscv/mm/cacheflush.c
> @@ -21,7 +21,9 @@ void flush_icache_all(void)
> {
> local_flush_icache_all();
>
> - if (riscv_use_sbi_for_rfence())
> + if (num_online_cpus() < 2)
with patch5, I think it's better to short cut for !SMP, I.E
if (!IS_ENABLED(CONFIG_SMP) || num_online_cpus()) < 2)
so that the UP case can avoid a atomic read and check
> + return;
> + else if (riscv_use_sbi_for_rfence())
> sbi_remote_fence_i(NULL);
> else
> on_each_cpu(ipi_remote_fence_i, NULL, 1);
> diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
> index 2f18fe6fc4f3..37b3c93e3c30 100644
> --- a/arch/riscv/mm/tlbflush.c
> +++ b/arch/riscv/mm/tlbflush.c
> @@ -73,7 +73,9 @@ static void __ipi_flush_tlb_all(void *info)
>
> void flush_tlb_all(void)
> {
> - if (riscv_use_sbi_for_rfence())
> + if (num_online_cpus() < 2)
ditto
> + local_flush_tlb_all();
> + else if (riscv_use_sbi_for_rfence())
> sbi_remote_sfence_vma_asid(NULL, 0, FLUSH_TLB_MAX_SIZE, FLUSH_TLB_NO_ASID);
> else
> on_each_cpu(__ipi_flush_tlb_all, NULL, 1);
> --
> 2.42.0
>
>
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