linux-kernel - [PATCH] riscv: tlbflush: remove confusing comment on local_flush_tlb

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Message-ID: <alpine.DEB.2.21.9999.1910141254360.12988@viisi.sifive.com>
Date:   Mon, 14 Oct 2019 12:55:49 -0700 (PDT)
From:   Paul Walmsley <paul.walmsley@...ive.com>
To:     linux-riscv@...ts.infradead.org
cc:     linux-kernel@...r.kernel.org, andrew@...ive.com, palmer@...ive.com,
        alankao@...estech.com
Subject: [PATCH] riscv: tlbflush: remove confusing comment on
 local_flush_tlb_all()


Remove a confusing comment on our local_flush_tlb_all()
implementation.  Per an internal discussion with Andrew, while it's
true that the fence.i is not necessary, it's not the case that an
sfence.vma implies a fence.i.  We also drop the section about
"flush[ing] the entire local TLB" to better align with the language in
section 4.2.1 "Supervisor Memory-Management Fence Instruction" of the
RISC-V Privileged Specification v20190608.

Fixes: c901e45a999a1 ("RISC-V: `sfence.vma` orderes the instruction cache")
Reported-by: Alan Kao <alankao@...estech.com>
Cc: Palmer Dabbelt <palmer@...ive.com>
Cc: Andrew Waterman <andrew@...ive.com>
Signed-off-by: Paul Walmsley <paul.walmsley@...ive.com>
---
 arch/riscv/include/asm/tlbflush.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h
index 37ae4e367ad2..f02188a5b0f4 100644
--- a/arch/riscv/include/asm/tlbflush.h
+++ b/arch/riscv/include/asm/tlbflush.h
@@ -10,10 +10,6 @@
 #include <linux/mm_types.h>
 #include <asm/smp.h>
 
-/*
- * Flush entire local TLB.  'sfence.vma' implicitly fences with the instruction
- * cache as well, so a 'fence.i' is not necessary.
- */
 static inline void local_flush_tlb_all(void)
 {
 	__asm__ __volatile__ ("sfence.vma" : : : "memory");
-- 
2.23.0