linux-kernel - [PATCH] implement flush_cache_vmap and flush_cache

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Date:   Mon, 29 Mar 2021 01:55:09 +0000
From:   Jiuyang Liu <liu@...yang.me>
To:     Alex Ghiti <alex@...ti.fr>
Cc:     Jiuyang Liu <liu@...yang.me>,
        Andrew Waterman <waterman@...s.berkeley.edu>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] implement flush_cache_vmap and flush_cache_vunmap for RISC-V

This patch implements flush_cache_vmap and flush_cache_vunmap for
RISC-V, since these functions might modify PTE. Without this patch,
SFENCE.VMA won't be added to related codes, which might introduce a bug
in some out-of-order micro-architecture implementations.

Signed-off-by: Jiuyang Liu <liu@...yang.me>
---
 arch/riscv/include/asm/cacheflush.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/riscv/include/asm/cacheflush.h b/arch/riscv/include/asm/cacheflush.h
index 23ff70350992..4adf25248c43 100644
--- a/arch/riscv/include/asm/cacheflush.h
+++ b/arch/riscv/include/asm/cacheflush.h
@@ -8,6 +8,14 @@
 
 #include <linux/mm.h>
 
+/*
+ * flush_cache_vmap and flush_cache_vunmap might modify PTE, needs SFENCE.VMA.
+ * - flush_cache_vmap is invoked after map_kernel_range() has installed the page table entries.
+ * - flush_cache_vunmap is invoked before unmap_kernel_range() deletes the page table entries
+ */
+#define flush_cache_vmap(start, end) flush_tlb_all()
+#define flush_cache_vunmap(start, end) flush_tlb_all()
+
 static inline void local_flush_icache_all(void)
 {
 	asm volatile ("fence.i" ::: "memory");
-- 
2.31.1