linux-kernel - [PATCH] asm-generic: flush icache only when vma->vm_flags has VM

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Date: Tue,  9 Jan 2024 22:45:59 +0800
From: Yangyu Chen <cyy@...self.name>
To: Arnd Bergmann <arnd@...db.de>
Cc: Christoph Hellwig <hch@....de>,
	Alexander Potapenko <glider@...gle.com>,
	Mike Frysinger <vapier@...too.org>,
	linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Yangyu Chen <cyy@...self.name>
Subject: [PATCH] asm-generic: flush icache only when vma->vm_flags has VM_EXEC set

For some ISAs like RISC-V, which may not support bus broadcast-based
icache flushing instructions, it's necessary to send IPIs to all of the
CPUs in the system to flush the icache. This process can be expensive for
these ISAs and introduce disturbances during performance profiling.
Limiting the icache flush to occur only when the vma->vm_flags has VM_EXEC
can help minimize the frequency of these operations.

Signed-off-by: Yangyu Chen <cyy@...self.name>
---
 include/asm-generic/cacheflush.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/asm-generic/cacheflush.h b/include/asm-generic/cacheflush.h
index 84ec53ccc450..729d51536575 100644
--- a/include/asm-generic/cacheflush.h
+++ b/include/asm-generic/cacheflush.h
@@ -102,7 +102,8 @@ static inline void flush_cache_vunmap(unsigned long start, unsigned long end)
 	do { \
 		instrument_copy_to_user((void __user *)dst, src, len); \
 		memcpy(dst, src, len); \
-		flush_icache_user_page(vma, page, vaddr, len); \
+		if (vma->vm_flags & VM_EXEC) \
+			flush_icache_user_page(vma, page, vaddr, len); \
 	} while (0)
 #endif
 
-- 
2.43.0