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From: Linhaifeng <haifeng.lin@huawei.com>
To: Jerin Jacob <jerinjacobk@gmail.com>
Cc: Gavin Hu <Gavin.Hu@arm.com>, "dev@dpdk.org" <dev@dpdk.org>,
	"thomas@monjalon.net" <thomas@monjalon.net>,
	chenchanghu <chenchanghu@huawei.com>,
	xudingke <xudingke@huawei.com>,
	"Lilijun (Jerry)" <jerry.lilijun@huawei.com>,
	Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
	Steve Capper <Steve.Capper@arm.com>, nd <nd@arm.com>
Subject: [dpdk-dev] [PATCH v6] eal/arm64: fix rdtsc precise version
Date: Wed, 11 Mar 2020 07:24:10 +0000	[thread overview]
Message-ID: <4099DE2E54AFAD489356C6C9161D53339729FAD0@DGGEML502-MBX.china.huawei.com> (raw)

In order to get more accurate the cntvct_el0 reading,
SW must invoke isb and arch_counter_enforce_ordering.

Reference of linux kernel:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/
linux.git/tree/arch/arm64/include/asm/arch_timer.h?h=v5.5#n220

Fixes: ccad39ea0712 ("eal/arm: add cpu cycle operations for ARMv8")
Cc: stable@dpdk.org

Reviewed-by: Jerin Jacob <jerinjacobk@gmail.com>
Reviewed-by: Gavin Hu <gavin.hu@arm.com>
Signed-off-by: Haifeng Lin <haifeng.lin@huawei.com>
---
 .../common/include/arch/arm/rte_cycles_64.h   | 26 +++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/lib/librte_eal/common/include/arch/arm/rte_cycles_64.h b/lib/librte_eal/common/include/arch/arm/rte_cycles_64.h
index 68e7c7338..6b0df5b0a 100644
--- a/lib/librte_eal/common/include/arch/arm/rte_cycles_64.h
+++ b/lib/librte_eal/common/include/arch/arm/rte_cycles_64.h
@@ -59,11 +59,33 @@ rte_rdtsc(void)
 }
 #endif
 
+static inline void
+isb(void)
+{
+	asm volatile("isb" : : : "memory");
+}
+
+static inline void
+__rte_arm64_cntvct_el0_enforce_ordering(uint64_t val)
+{
+	uint64_t tmp;
+
+	asm volatile(
+	"	eor	%0, %1, %1\n"
+	"	add	%0, sp, %0\n"
+	"	ldr	xzr, [%0]"
+	: "=r" (tmp) : "r" (val));
+}
+
 static inline uint64_t
 rte_rdtsc_precise(void)
 {
-	rte_mb();
-	return rte_rdtsc();
+	uint64_t tsc;
+
+	isb();
+	tsc = rte_rdtsc();
+	__rte_arm64_cntvct_el0_enforce_ordering(tsc);
+	return tsc;
 }
 
 static inline uint64_t
-- 
2.24.1.windows.2


             reply	other threads:[~2020-03-11  7:24 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-11  7:24 Linhaifeng [this message]
2020-03-11  9:38 ` David Marchand
2020-03-12  0:57   ` Linhaifeng

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