From 6b6de68c63eda6240ec92e44b998f910156f8806 Mon Sep 17 00:00:00 2001
From: Christian Borntraeger <borntraeger@de.ibm.com>
Date: Tue, 9 Feb 2016 13:47:55 +0100
Subject: KVM: halt_polling: improve grow/shrink settings
Right now halt_poll_ns can be change during runtime. The
grow and shrink factors can only be set during module load.
Lets fix several aspects of grow shrink:
- make grow/shrink changeable by root
- make all variables unsigned int
- read the variables once to prevent races
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
virt/kvm/kvm_main.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
(limited to 'virt')
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index a11cfd20a6a0..ba45e41c3210 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -72,11 +72,11 @@ module_param(halt_poll_ns, uint, S_IRUGO | S_IWUSR);
/* Default doubles per-vcpu halt_poll_ns. */
static unsigned int halt_poll_ns_grow = 2;
-module_param(halt_poll_ns_grow, int, S_IRUGO);
+module_param(halt_poll_ns_grow, uint, S_IRUGO | S_IWUSR);
/* Default resets per-vcpu halt_poll_ns . */
static unsigned int halt_poll_ns_shrink;
-module_param(halt_poll_ns_shrink, int, S_IRUGO);
+module_param(halt_poll_ns_shrink, uint, S_IRUGO | S_IWUSR);
/*
* Ordering of locks:
@@ -1943,14 +1943,15 @@ EXPORT_SYMBOL_GPL(kvm_vcpu_mark_page_dirty);
static void grow_halt_poll_ns(struct kvm_vcpu *vcpu)
{
- int old, val;
+ unsigned int old, val, grow;
old = val = vcpu->halt_poll_ns;
+ grow = READ_ONCE(halt_poll_ns_grow);
/* 10us base */
- if (val == 0 && halt_poll_ns_grow)
+ if (val == 0 && grow)
val = 10000;
else
- val *= halt_poll_ns_grow;
+ val *= grow;
vcpu->halt_poll_ns = val;
trace_kvm_halt_poll_ns_grow(vcpu->vcpu_id, val, old);
@@ -1958,13 +1959,14 @@ static void grow_halt_poll_ns(struct kvm_vcpu *vcpu)
static void shrink_halt_poll_ns(struct kvm_vcpu *vcpu)
{
- int old, val;
+ unsigned int old, val, shrink;
old = val = vcpu->halt_poll_ns;
- if (halt_poll_ns_shrink == 0)
+ shrink = READ_ONCE(halt_poll_ns_shrink);
+ if (shrink == 0)
val = 0;
else
- val /= halt_poll_ns_shrink;
+ val /= shrink;
vcpu->halt_poll_ns = val;
trace_kvm_halt_poll_ns_shrink(vcpu->vcpu_id, val, old);
--
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