Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 0061d53d authored by Marcelo Tosatti's avatar Marcelo Tosatti Committed by Gleb Natapov
Browse files

KVM: x86: limit difference between kvmclock updates 



kvmclock updates which are isolated to a given vcpu, such as vcpu->cpu
migration, should not allow system_timestamp from the rest of the vcpus
to remain static. Otherwise ntp frequency correction applies to one
vcpu's system_timestamp but not the others.

So in those cases, request a kvmclock update for all vcpus. The worst
case for a remote vcpu to update its kvmclock is then bounded by maximum
nohz sleep latency.

Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: default avatarGleb Natapov <gleb@redhat.com>
parent f1ed0450

arch/x86/kvm/x86.c

+28 −2
Original line number Diff line number Diff line
@@ -1588,6 +1588,30 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) 
	return 0;

}



/*

 * kvmclock updates which are isolated to a given vcpu, such as

 * vcpu->cpu migration, should not allow system_timestamp from

 * the rest of the vcpus to remain static. Otherwise ntp frequency

 * correction applies to one vcpu's system_timestamp but not

 * the others.

 *

 * So in those cases, request a kvmclock update for all vcpus.

 * The worst case for a remote vcpu to update its kvmclock

 * is then bounded by maximum nohz sleep latency.

 */



static void kvm_gen_kvmclock_update(struct kvm_vcpu *v)

{

	int i;

	struct kvm *kvm = v->kvm;

	struct kvm_vcpu *vcpu;



	kvm_for_each_vcpu(i, vcpu, kvm) {

		set_bit(KVM_REQ_CLOCK_UPDATE, &vcpu->requests);

		kvm_vcpu_kick(vcpu);

	}

}



static bool msr_mtrr_valid(unsigned msr)

{

	switch (msr) {
@@ -1985,7 +2009,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) 
		kvmclock_reset(vcpu);



		vcpu->arch.time = data;

		kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);

		kvm_make_request(KVM_REQ_GLOBAL_CLOCK_UPDATE, vcpu);



		/* we verify if the enable bit is set... */

		if (!(data & 1))
@@ -2702,7 +2726,7 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) 
		 * kvmclock on vcpu->cpu migration

		 */

		if (!vcpu->kvm->arch.use_master_clock || vcpu->cpu == -1)

			kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);

			kvm_make_request(KVM_REQ_GLOBAL_CLOCK_UPDATE, vcpu);

		if (vcpu->cpu != cpu)

			kvm_migrate_timers(vcpu);

		vcpu->cpu = cpu;
@@ -5703,6 +5727,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) 
			__kvm_migrate_timers(vcpu);

		if (kvm_check_request(KVM_REQ_MASTERCLOCK_UPDATE, vcpu))

			kvm_gen_update_masterclock(vcpu->kvm);

		if (kvm_check_request(KVM_REQ_GLOBAL_CLOCK_UPDATE, vcpu))

			kvm_gen_kvmclock_update(vcpu);

		if (kvm_check_request(KVM_REQ_CLOCK_UPDATE, vcpu)) {

			r = kvm_guest_time_update(vcpu);

			if (unlikely(r))

include/linux/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -124,6 +124,7 @@ static inline bool is_error_page(struct page *page) 
#define KVM_REQ_MCLOCK_INPROGRESS 19

#define KVM_REQ_EPR_EXIT          20

#define KVM_REQ_SCAN_IOAPIC       21

#define KVM_REQ_GLOBAL_CLOCK_UPDATE 22



#define KVM_USERSPACE_IRQ_SOURCE_ID		0

#define KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID	1