linux-kernel - [PATCH v2 3/4] cpuidle-haltpoll: ensure cpu_halt_poll

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Message-Id: <1573031332-2121-4-git-send-email-zhenzhong.duan@oracle.com>
Date:   Wed,  6 Nov 2019 17:08:51 +0800
From:   Zhenzhong Duan <zhenzhong.duan@...cle.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     pbonzini@...hat.com, rkrcmar@...hat.com,
        rafael.j.wysocki@...el.com, joao.m.martins@...cle.com,
        mtosatti@...hat.com, Zhenzhong Duan <zhenzhong.duan@...cle.com>
Subject: [PATCH v2 3/4] cpuidle-haltpoll: ensure cpu_halt_poll_us in right scope

As user can adjust guest_halt_poll_grow_start and guest_halt_poll_ns
which leads to cpu_halt_poll_us beyond the two boundaries. This patch
ensures cpu_halt_poll_us in that scope.

If guest_halt_poll_shrink is 0, shrink the cpu_halt_poll_us to
guest_halt_poll_grow_start instead of 0. To disable poll we can set
guest_halt_poll_ns to 0.

If user wrongly set guest_halt_poll_grow_start > guest_halt_poll_ns > 0,
guest_halt_poll_ns take precedency and poll time is a fixed value of
guest_halt_poll_ns.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@...cle.com>
---
 drivers/cpuidle/governors/haltpoll.c | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/drivers/cpuidle/governors/haltpoll.c b/drivers/cpuidle/governors/haltpoll.c
index 660859d..d0b38b53 100644
--- a/drivers/cpuidle/governors/haltpoll.c
+++ b/drivers/cpuidle/governors/haltpoll.c
@@ -97,32 +97,30 @@ static int haltpoll_select(struct cpuidle_driver *drv,
 
 static void adjust_poll_limit(struct cpuidle_device *dev, unsigned int block_us)
 {
-	unsigned int val;
+	unsigned int val = dev->poll_limit_ns;
 	u64 block_ns = block_us*NSEC_PER_USEC;
 
 	/* Grow cpu_halt_poll_us if
-	 * cpu_halt_poll_us < block_ns < guest_halt_poll_us
+	 * cpu_halt_poll_us < block_ns <= guest_halt_poll_us
 	 */
-	if (block_ns > dev->poll_limit_ns && block_ns <= guest_halt_poll_ns) {
+	if (block_ns > dev->poll_limit_ns && block_ns <= guest_halt_poll_ns &&
+	    guest_halt_poll_grow)
 		val = dev->poll_limit_ns * guest_halt_poll_grow;
-
-		if (val < guest_halt_poll_grow_start)
-			val = guest_halt_poll_grow_start;
-		if (val > guest_halt_poll_ns)
-			val = guest_halt_poll_ns;
-
-		dev->poll_limit_ns = val;
-	} else if (block_ns > guest_halt_poll_ns &&
-		   guest_halt_poll_allow_shrink) {
+	else if (block_ns > guest_halt_poll_ns &&
+			guest_halt_poll_allow_shrink) {
 		unsigned int shrink = guest_halt_poll_shrink;
 
-		val = dev->poll_limit_ns;
 		if (shrink == 0)
-			val = 0;
+			val = guest_halt_poll_grow_start;
 		else
 			val /= shrink;
-		dev->poll_limit_ns = val;
 	}
+	if (val < guest_halt_poll_grow_start)
+		val = guest_halt_poll_grow_start;
+	if (val > guest_halt_poll_ns)
+		val = guest_halt_poll_ns;
+
+	dev->poll_limit_ns = val;
 }
 
 /**
-- 
1.8.3.1