summaryrefslogtreecommitdiffstats
path: root/arch/x86/kvm/i8254.c
diff options
context:
space:
mode:
authorMarcelo Tosatti <mtosatti@redhat.com>2014-01-06 12:00:02 -0200
committerPaolo Bonzini <pbonzini@redhat.com>2014-01-15 12:43:54 +0100
commit9ed96e87c5748de4c2807ef17e81287c7304186c (patch)
treee16371f8aedac885b770d1db402b03847f519b8e /arch/x86/kvm/i8254.c
parent37f6a4e237303549c8676dfe1fd1991ceab512eb (diff)
downloadlinux-9ed96e87c5748de4c2807ef17e81287c7304186c.tar.bz2
KVM: x86: limit PIT timer frequency
Limit PIT timer frequency similarly to the limit applied by LAPIC timer. Cc: stable@kernel.org Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/i8254.c')
-rw-r--r--arch/x86/kvm/i8254.c18
1 files changed, 18 insertions, 0 deletions
diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index 412a5aa0ef94..518d86471b76 100644
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -37,6 +37,7 @@
#include "irq.h"
#include "i8254.h"
+#include "x86.h"
#ifndef CONFIG_X86_64
#define mod_64(x, y) ((x) - (y) * div64_u64(x, y))
@@ -349,6 +350,23 @@ static void create_pit_timer(struct kvm *kvm, u32 val, int is_period)
atomic_set(&ps->pending, 0);
ps->irq_ack = 1;
+ /*
+ * Do not allow the guest to program periodic timers with small
+ * interval, since the hrtimers are not throttled by the host
+ * scheduler.
+ */
+ if (ps->is_periodic) {
+ s64 min_period = min_timer_period_us * 1000LL;
+
+ if (ps->period < min_period) {
+ pr_info_ratelimited(
+ "kvm: requested %lld ns "
+ "i8254 timer period limited to %lld ns\n",
+ ps->period, min_period);
+ ps->period = min_period;
+ }
+ }
+
hrtimer_start(&ps->timer, ktime_add_ns(ktime_get(), interval),
HRTIMER_MODE_ABS);
}