On 2014-01-06 15:00, Marcelo Tosatti wrote: > > > Limit PIT timer frequency similarly to the limit applied by > LAPIC timer. > > Cc: [email protected] > Signed-off-by: Marcelo Tosatti <[email protected]> > > diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c > index 412a5aa..518d864 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); > } > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index dec48bf..7f4dfa6 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -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; > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 5d004da..d89d51b 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -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; > diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h > index 587fb9e..8da5823 100644 > --- a/arch/x86/kvm/x86.h > +++ b/arch/x86/kvm/x86.h > @@ -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 >
Indeed, required here as well. Reviewed-by: Jan Kiszka <[email protected]> At this chance, I also grep'ed through timer emulations of other archs. Only MIPS uses a periodic hrtimer, but with a fixed frequency. So we should be safe for now. Jan
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