From 6b6de68c63eda6240ec92e44b998f910156f8806 Mon Sep 17 00:00:00 2001 From: Christian Borntraeger Date: Tue, 9 Feb 2016 13:47:55 +0100 Subject: [PATCH] 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 Signed-off-by: Paolo Bonzini --- include/trace/events/kvm.h | 9 +++++---- virt/kvm/kvm_main.c | 18 ++++++++++-------- 2 files changed, 15 insertions(+), 12 deletions(-) diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h index d6f83222a6a1..aa69253ecc7d 100644 --- a/include/trace/events/kvm.h +++ b/include/trace/events/kvm.h @@ -359,14 +359,15 @@ TRACE_EVENT( #endif TRACE_EVENT(kvm_halt_poll_ns, - TP_PROTO(bool grow, unsigned int vcpu_id, int new, int old), + TP_PROTO(bool grow, unsigned int vcpu_id, unsigned int new, + unsigned int old), TP_ARGS(grow, vcpu_id, new, old), TP_STRUCT__entry( __field(bool, grow) __field(unsigned int, vcpu_id) - __field(int, new) - __field(int, old) + __field(unsigned int, new) + __field(unsigned int, old) ), TP_fast_assign( @@ -376,7 +377,7 @@ TRACE_EVENT(kvm_halt_poll_ns, __entry->old = old; ), - TP_printk("vcpu %u: halt_poll_ns %d (%s %d)", + TP_printk("vcpu %u: halt_poll_ns %u (%s %u)", __entry->vcpu_id, __entry->new, __entry->grow ? "grow" : "shrink", 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); -- 2.20.1