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KVM: x86: limit PIT timer frequency

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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>
This commit is contained in:
Marcelo Tosatti
2014-01-06 12:00:02 -02:00
committed by Paolo Bonzini
parent 37f6a4e237
commit 9ed96e87c5
4 changed files with 23 additions and 3 deletions
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18
arch/x86/kvm/i8254.c
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@@ -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);
}