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@xxxxxxxxxx>
---
Changes in v6:
- Clarify the commit message for patch 8 based on ML discussion
Changes in v4:
- Only set tlb_flush_all_threshold when CONFIG_MMU=y.
Changes in v3:
- New patch for v3
arch/riscv/errata/sifive/errata.c | 5 +++++
arch/riscv/include/asm/tlbflush.h | 2 ++
arch/riscv/mm/tlbflush.c | 2 +-
3 files changed, 8 insertions(+), 1 deletion(-)
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;
}
diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h
index 463b615d7728..8e329721375b 100644
--- a/arch/riscv/include/asm/tlbflush.h
+++ b/arch/riscv/include/asm/tlbflush.h
@@ -66,6 +66,8 @@ void arch_tlbbatch_add_pending(struct arch_tlbflush_unmap_batch *batch,
unsigned long uaddr);
void arch_flush_tlb_batched_pending(struct mm_struct *mm);
void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch);
+
+extern unsigned long tlb_flush_all_threshold;
#else /* CONFIG_MMU */
#define local_flush_tlb_all() do { } while (0)
#endif /* CONFIG_MMU */
diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
index ad7bdcfcc219..18af7b5053af 100644
--- a/arch/riscv/mm/tlbflush.c
+++ b/arch/riscv/mm/tlbflush.c
@@ -11,7 +11,7 @@
* Flush entire TLB if number of entries to be flushed is greater
* than the threshold below.
*/
-static unsigned long tlb_flush_all_threshold __read_mostly = 64;
+unsigned long tlb_flush_all_threshold __read_mostly = 64;
static void local_flush_tlb_range_threshold_asid(unsigned long start,
unsigned long size,
--
2.43.1
