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Commit 16e8d74d authored by Marcelo Tosatti's avatar Marcelo Tosatti
Browse files

KVM: x86: notifier for clocksource changes 



Register a notifier for clocksource change event. In case
the host switches to clock other than TSC, disable master
clock usage.

Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent e0b306fe

arch/x86/kvm/x86.c

+93 −1
Original line number Diff line number Diff line
@@ -46,6 +46,8 @@ 
#include <linux/uaccess.h>

#include <linux/hash.h>

#include <linux/pci.h>

#include <linux/timekeeper_internal.h>

#include <linux/pvclock_gtod.h>

#include <trace/events/kvm.h>



#define CREATE_TRACE_POINTS
@@ -901,6 +903,55 @@ static int do_set_msr(struct kvm_vcpu *vcpu, unsigned index, u64 *data) 
	return kvm_set_msr(vcpu, index, *data);

}



#ifdef CONFIG_X86_64

struct pvclock_gtod_data {

	seqcount_t	seq;



	struct { /* extract of a clocksource struct */

		int vclock_mode;

		cycle_t	cycle_last;

		cycle_t	mask;

		u32	mult;

		u32	shift;

	} clock;



	/* open coded 'struct timespec' */

	u64		monotonic_time_snsec;

	time_t		monotonic_time_sec;

};



static struct pvclock_gtod_data pvclock_gtod_data;



static void update_pvclock_gtod(struct timekeeper *tk)

{

	struct pvclock_gtod_data *vdata = &pvclock_gtod_data;



	write_seqcount_begin(&vdata->seq);



	/* copy pvclock gtod data */

	vdata->clock.vclock_mode	= tk->clock->archdata.vclock_mode;

	vdata->clock.cycle_last		= tk->clock->cycle_last;

	vdata->clock.mask		= tk->clock->mask;

	vdata->clock.mult		= tk->mult;

	vdata->clock.shift		= tk->shift;



	vdata->monotonic_time_sec	= tk->xtime_sec

					+ tk->wall_to_monotonic.tv_sec;

	vdata->monotonic_time_snsec	= tk->xtime_nsec

					+ (tk->wall_to_monotonic.tv_nsec

						<< tk->shift);

	while (vdata->monotonic_time_snsec >=

					(((u64)NSEC_PER_SEC) << tk->shift)) {

		vdata->monotonic_time_snsec -=

					((u64)NSEC_PER_SEC) << tk->shift;

		vdata->monotonic_time_sec++;

	}



	write_seqcount_end(&vdata->seq);

}

#endif





static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock)

{

	int version;
@@ -997,6 +1048,8 @@ static inline u64 get_kernel_ns(void) 
	return timespec_to_ns(&ts);

}



static atomic_t kvm_guest_has_master_clock = ATOMIC_INIT(0);



static DEFINE_PER_CPU(unsigned long, cpu_tsc_khz);

unsigned long max_tsc_khz;
@@ -1229,7 +1282,6 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) 
	vcpu->last_kernel_ns = kernel_ns;

	vcpu->last_guest_tsc = tsc_timestamp;





	/*

	 * The interface expects us to write an even number signaling that the

	 * update is finished. Since the guest won't see the intermediate
@@ -4857,6 +4909,39 @@ static void kvm_set_mmio_spte_mask(void) 
	kvm_mmu_set_mmio_spte_mask(mask);

}



#ifdef CONFIG_X86_64

static void pvclock_gtod_update_fn(struct work_struct *work)

{

}



static DECLARE_WORK(pvclock_gtod_work, pvclock_gtod_update_fn);



/*

 * Notification about pvclock gtod data update.

 */

static int pvclock_gtod_notify(struct notifier_block *nb, unsigned long unused,

			       void *priv)

{

	struct pvclock_gtod_data *gtod = &pvclock_gtod_data;

	struct timekeeper *tk = priv;



	update_pvclock_gtod(tk);



	/* disable master clock if host does not trust, or does not

	 * use, TSC clocksource

	 */

	if (gtod->clock.vclock_mode != VCLOCK_TSC &&

	    atomic_read(&kvm_guest_has_master_clock) != 0)

		queue_work(system_long_wq, &pvclock_gtod_work);



	return 0;

}



static struct notifier_block pvclock_gtod_notifier = {

	.notifier_call = pvclock_gtod_notify,

};

#endif



int kvm_arch_init(void *opaque)

{

	int r;
@@ -4898,6 +4983,10 @@ int kvm_arch_init(void *opaque) 
		host_xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);



	kvm_lapic_init();

#ifdef CONFIG_X86_64

	pvclock_gtod_register_notifier(&pvclock_gtod_notifier);

#endif



	return 0;



out:
@@ -4912,6 +5001,9 @@ void kvm_arch_exit(void) 
		cpufreq_unregister_notifier(&kvmclock_cpufreq_notifier_block,

					    CPUFREQ_TRANSITION_NOTIFIER);

	unregister_hotcpu_notifier(&kvmclock_cpu_notifier_block);

#ifdef CONFIG_X86_64

	pvclock_gtod_unregister_notifier(&pvclock_gtod_notifier);

#endif

	kvm_x86_ops = NULL;

	kvm_mmu_module_exit();

}