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>
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@ -37,6 +37,7 @@
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#include "irq.h"
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#include "i8254.h"
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#include "x86.h"
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#ifndef CONFIG_X86_64
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#define mod_64(x, y) ((x) - (y) * div64_u64(x, y))
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@ -349,6 +350,23 @@ static void create_pit_timer(struct kvm *kvm, u32 val, int is_period)
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atomic_set(&ps->pending, 0);
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ps->irq_ack = 1;
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/*
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* Do not allow the guest to program periodic timers with small
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* interval, since the hrtimers are not throttled by the host
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* scheduler.
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*/
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if (ps->is_periodic) {
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s64 min_period = min_timer_period_us * 1000LL;
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if (ps->period < min_period) {
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pr_info_ratelimited(
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"kvm: requested %lld ns "
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"i8254 timer period limited to %lld ns\n",
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ps->period, min_period);
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ps->period = min_period;
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}
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}
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hrtimer_start(&ps->timer, ktime_add_ns(ktime_get(), interval),
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HRTIMER_MODE_ABS);
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}
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@ -71,9 +71,6 @@
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#define VEC_POS(v) ((v) & (32 - 1))
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#define REG_POS(v) (((v) >> 5) << 4)
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static unsigned int min_timer_period_us = 500;
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module_param(min_timer_period_us, uint, S_IRUGO | S_IWUSR);
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static inline void apic_set_reg(struct kvm_lapic *apic, int reg_off, u32 val)
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{
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*((u32 *) (apic->regs + reg_off)) = val;
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@ -94,6 +94,9 @@ EXPORT_SYMBOL_GPL(kvm_x86_ops);
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static bool ignore_msrs = 0;
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module_param(ignore_msrs, bool, S_IRUGO | S_IWUSR);
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unsigned int min_timer_period_us = 500;
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module_param(min_timer_period_us, uint, S_IRUGO | S_IWUSR);
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bool kvm_has_tsc_control;
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EXPORT_SYMBOL_GPL(kvm_has_tsc_control);
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u32 kvm_max_guest_tsc_khz;
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@ -125,5 +125,7 @@ int kvm_write_guest_virt_system(struct x86_emulate_ctxt *ctxt,
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#define KVM_SUPPORTED_XCR0 (XSTATE_FP | XSTATE_SSE | XSTATE_YMM)
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extern u64 host_xcr0;
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extern unsigned int min_timer_period_us;
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extern struct static_key kvm_no_apic_vcpu;
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#endif
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