linux-kernel - [PATCH V2] x86/Hyper-V: don't allocate clockevent device when synthetic timer is unavailable

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Message-Id: <20200331021738.2572-1-Tianyu.Lan@microsoft.com>
Date:   Mon, 30 Mar 2020 19:17:38 -0700
From:   ltykernel@...il.com
To:     kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        x86@...nel.org, michael.h.kelley@...rosoft.com, wei.liu@...nel.org
Cc:     Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        devel@...uxdriverproject.org, linux-kernel@...r.kernel.org,
        vkuznets@...hat.com
Subject: [PATCH V2] x86/Hyper-V: don't allocate clockevent device when synthetic timer is unavailable

From: Tianyu Lan <Tianyu.Lan@...rosoft.com>

Current code initializes clock event data structure for syn timer
even when it's unavailable. Fix it.

Signed-off-by: Tianyu Lan <Tianyu.Lan@...rosoft.com>
---
Change since v1:
	Update title and commit log. 

 drivers/hv/hv.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 632d25674e7f..2e893768fc76 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -212,13 +212,16 @@ int hv_synic_alloc(void)
 		tasklet_init(&hv_cpu->msg_dpc,
 			     vmbus_on_msg_dpc, (unsigned long) hv_cpu);
 
-		hv_cpu->clk_evt = kzalloc(sizeof(struct clock_event_device),
-					  GFP_KERNEL);
-		if (hv_cpu->clk_evt == NULL) {
-			pr_err("Unable to allocate clock event device\n");
-			goto err;
+		if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
+			hv_cpu->clk_evt =
+				kzalloc(sizeof(struct clock_event_device),
+						  GFP_KERNEL);
+			if (hv_cpu->clk_evt == NULL) {
+				pr_err("Unable to allocate clock event device\n");
+				goto err;
+			}
+			hv_init_clockevent_device(hv_cpu->clk_evt, cpu);
 		}
-		hv_init_clockevent_device(hv_cpu->clk_evt, cpu);
 
 		hv_cpu->synic_message_page =
 			(void *)get_zeroed_page(GFP_ATOMIC);
-- 
2.14.5