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Commit 9ed96e87 authored by Marcelo Tosatti's avatar Marcelo Tosatti Committed by Paolo Bonzini
Browse files

KVM: x86: limit PIT timer frequency 



Limit PIT timer frequency similarly to the limit applied by
LAPIC timer.

Cc: stable@kernel.org
Reviewed-by: default avatarJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 37f6a4e2

arch/x86/kvm/i8254.c

+18 −0
Original line number Diff line number Diff line
@@ -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);

}

arch/x86/kvm/lapic.c

+0 −3
Original line number Diff line number Diff line
@@ -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;

arch/x86/kvm/x86.c

+3 −0
Original line number Diff line number Diff line
@@ -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;

arch/x86/kvm/x86.h

+2 −0
Original line number Diff line number Diff line
@@ -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