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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
View file

@ -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);
}

3
arch/x86/kvm/lapic.c
View file

@ -71,9 +71,6 @@
#define VEC_POS(v) ((v) & (32 - 1))
#define REG_POS(v) (((v) >> 5) << 4)
static unsigned int min_timer_period_us = 500;
module_param(min_timer_period_us, uint, S_IRUGO | S_IWUSR);
static inline void apic_set_reg(struct kvm_lapic *apic, int reg_off, u32 val)
{
*((u32 *) (apic->regs + reg_off)) = val;

3
arch/x86/kvm/x86.c
View file

@ -94,6 +94,9 @@ EXPORT_SYMBOL_GPL(kvm_x86_ops);
static bool ignore_msrs = 0;
module_param(ignore_msrs, bool, S_IRUGO | S_IWUSR);
unsigned int min_timer_period_us = 500;
module_param(min_timer_period_us, uint, S_IRUGO | S_IWUSR);
bool kvm_has_tsc_control;
EXPORT_SYMBOL_GPL(kvm_has_tsc_control);
u32 kvm_max_guest_tsc_khz;

2
arch/x86/kvm/x86.h
View file

@ -125,5 +125,7 @@ int kvm_write_guest_virt_system(struct x86_emulate_ctxt *ctxt,
#define KVM_SUPPORTED_XCR0 (XSTATE_FP | XSTATE_SSE | XSTATE_YMM)
extern u64 host_xcr0;
extern unsigned int min_timer_period_us;
extern struct static_key kvm_no_apic_vcpu;
#endif