linux-kernel - [PATCH 1/6] Drivers: hv: vmbus: Get the current time from the current clocksource

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Message-Id: <1495129567-13744-1-git-send-email-kys@exchange.microsoft.com>
Date:   Thu, 18 May 2017 10:46:02 -0700
From:   kys@...hange.microsoft.com
To:     gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        devel@...uxdriverproject.org, olaf@...fle.de, apw@...onical.com,
        vkuznets@...hat.com, jasowang@...hat.com,
        leann.ogasawara@...onical.com, marcelo.cerri@...onical.com,
        sthemmin@...rosoft.com
Cc:     "K. Y. Srinivasan" <kys@...rosoft.com>
Subject: [PATCH 1/6] Drivers: hv: vmbus: Get the current time from the current clocksource

From: K. Y. Srinivasan <kys@...rosoft.com>

The current code uses the MSR based mechanism to get the current tick.
Use the current clock source as that might be more optimal.

Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
---
 arch/x86/include/asm/mshyperv.h |    1 -
 drivers/hv/hv.c                 |    2 +-
 2 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 7c9c895..7b07853 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -137,7 +137,6 @@ static inline void vmbus_signal_eom(struct hv_message *msg, u32 old_msg_type)
 	}
 }
 
-#define hv_get_current_tick(tick) rdmsrl(HV_X64_MSR_TIME_REF_COUNT, tick)
 #define hv_init_timer(timer, tick) wrmsrl(timer, tick)
 #define hv_init_timer_config(config, val) wrmsrl(config, val)
 
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 12e7bae..61fc8ce 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -96,7 +96,7 @@ static int hv_ce_set_next_event(unsigned long delta,
 
 	WARN_ON(!clockevent_state_oneshot(evt));
 
-	hv_get_current_tick(current_tick);
+	current_tick = hyperv_cs->read(NULL);
 	current_tick += delta;
 	hv_init_timer(HV_X64_MSR_STIMER0_COUNT, current_tick);
 	return 0;
-- 
1.7.1