linux-kernel - [PATCH] RISC-V: only flush icache when it has VM

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Message-ID: <tencent_6D851035F6F2FD0B5A69FB391AE39AC6300A@qq.com>
Date: Wed, 10 Jan 2024 02:48:59 +0800
From: Yangyu Chen <cyy@...self.name>
To: linux-riscv@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Alexandre Ghiti <alexghiti@...osinc.com>,
	Conor Dooley <conor.dooley@...rochip.com>,
	Jisheng Zhang <jszhang@...nel.org>,
	Andrew Waterman <andrew@...ive.com>,
	Yangyu Chen <cyy@...self.name>
Subject: [PATCH] RISC-V: only flush icache when it has VM_EXEC set

As I-Cache flush on current RISC-V needs to send IPIs to every CPU cores
in the system is very costly, limiting flush_icache_mm to be called only
when vma->vm_flags has VM_EXEC can help minimize the frequency of these
operations. It improves performance and reduces disturbances when
copy_from_user_page is needed such as profiling with perf.

For I-D coherence concerns, it will not fail if such a page adds VM_EXEC
flags in the future since we have checked it in the __set_pte_at function.

Signed-off-by: Yangyu Chen <cyy@...self.name>
---
 arch/riscv/include/asm/cacheflush.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/include/asm/cacheflush.h b/arch/riscv/include/asm/cacheflush.h
index 3cb53c4df27c..915f532dc336 100644
--- a/arch/riscv/include/asm/cacheflush.h
+++ b/arch/riscv/include/asm/cacheflush.h
@@ -33,8 +33,11 @@ static inline void flush_dcache_page(struct page *page)
  * so instead we just flush the whole thing.
  */
 #define flush_icache_range(start, end) flush_icache_all()
-#define flush_icache_user_page(vma, pg, addr, len) \
-	flush_icache_mm(vma->vm_mm, 0)
+#define flush_icache_user_page(vma, pg, addr, len)	\
+do {							\
+	if (vma->vm_flags & VM_EXEC)			\
+		flush_icache_mm(vma->vm_mm, 0);		\
+} while (0)
 
 #ifdef CONFIG_64BIT
 #define flush_cache_vmap(start, end)	flush_tlb_kernel_range(start, end)
-- 
2.43.0