From: Jens Axboe <axboe@kernel.dk>
Date: Thu, 22 Sep 2022 16:03:51 +0000 (-0600)
Subject: arm64: ensure CPU clock retrieval issues isb()
X-Git-Tag: fio-3.33~36
X-Git-Url: https://git.kernel.dk/?p=fio.git;a=commitdiff_plain;h=0574e8c3b2b47e1e2564c2f50ea0b6f2629f2e48

arm64: ensure CPU clock retrieval issues isb()

This prevents counter value speculation, which will otherwise cause
issues with the CPU clock.

Link: https://github.com/axboe/fio/issues/1472
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/arch/arch-aarch64.h b/arch/arch-aarch64.h
index 951d1718..919e5796 100644
--- a/arch/arch-aarch64.h
+++ b/arch/arch-aarch64.h
@@ -27,10 +27,13 @@ static inline int arch_ffz(unsigned long bitmask)
 
 #define ARCH_HAVE_FFZ
 
+#define isb()	asm volatile("isb" : : : "memory")
+
 static inline unsigned long long get_cpu_clock(void)
 {
 	unsigned long val;
 
+	isb();
 	asm volatile("mrs %0, cntvct_el0" : "=r" (val));
 	return val;
 }