From 9546f00410ed88b8117388cfd74ea59f4616a158 Mon Sep 17 00:00:00 2001 From: Samuel Holland Date: Tue, 26 Mar 2024 21:49:46 -0700 Subject: [PATCH] riscv: Only send remote fences when some other CPU is online 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 Reviewed-by: Alexandre Ghiti Link: https://lore.kernel.org/r/20240327045035.368512-6-samuel.holland@sifive.com Signed-off-by: Palmer Dabbelt --- 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 d76fc73e594b..f5be1fec8191 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) + 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 da821315d43e..0901aa47b58f 100644 --- a/arch/riscv/mm/tlbflush.c +++ b/arch/riscv/mm/tlbflush.c @@ -79,7 +79,9 @@ static void __ipi_flush_tlb_all(void *info) void flush_tlb_all(void) { - if (riscv_use_sbi_for_rfence()) + if (num_online_cpus() < 2) + 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);