From d6dcdabafcd7c612b164079d00da6d9775863a0b Mon Sep 17 00:00:00 2001
From: Samuel Holland <samuel.holland@sifive.com>
Date: Tue, 26 Mar 2024 21:49:49 -0700
Subject: riscv: Avoid TLB flush loops when affected by SiFive CIP-1200

Implementations affected by SiFive errata CIP-1200 have a bug which
forces the kernel to always use the global variant of the sfence.vma
instruction. When affected by this errata, do not attempt to flush a
range of addresses; each iteration of the loop would actually flush the
whole TLB instead. Instead, minimize the overall number of sfence.vma
instructions.

Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Reviewed-by: Yunhui Cui <cuiyunhui@bytedance.com>
Link: https://lore.kernel.org/r/20240327045035.368512-9-samuel.holland@sifive.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
---
 arch/riscv/errata/sifive/errata.c | 5 +++++
 1 file changed, 5 insertions(+)

(limited to 'arch/riscv/errata')

diff --git a/arch/riscv/errata/sifive/errata.c b/arch/riscv/errata/sifive/errata.c
index 3d9a32d791f7..716cfedad3a2 100644
--- a/arch/riscv/errata/sifive/errata.c
+++ b/arch/riscv/errata/sifive/errata.c
@@ -42,6 +42,11 @@ static bool errata_cip_1200_check_func(unsigned long  arch_id, unsigned long imp
 		return false;
 	if ((impid & 0xffffff) > 0x200630 || impid == 0x1200626)
 		return false;
+
+#ifdef CONFIG_MMU
+	tlb_flush_all_threshold = 0;
+#endif
+
 	return true;
 }
 
-- 
cgit