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Commit 0d6dd2ff authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

KVM: x86: always fill in vcpu->arch.hv_clock 



We will use it in the next patches for KVM_GET_CLOCK and as a basis for the
contents of the Hyper-V TSC page.  Get the values from the Linux
timekeeper even if kvmclock is not enabled.

Reviewed-by: default avatarRoman Kagan <rkagan@virtuozzo.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 4f5758fc

arch/x86/kvm/x86.c

+59 −50
Original line number Diff line number Diff line
@@ -1722,6 +1722,60 @@ static void kvm_gen_update_masterclock(struct kvm *kvm) 
#endif

}



static void kvm_setup_pvclock_page(struct kvm_vcpu *v)

{

	struct kvm_vcpu_arch *vcpu = &v->arch;

	struct pvclock_vcpu_time_info guest_hv_clock;



	if (unlikely(kvm_read_guest_cached(v->kvm, &vcpu->pv_time,

		&guest_hv_clock, sizeof(guest_hv_clock))))

		return;



	/* This VCPU is paused, but it's legal for a guest to read another

	 * VCPU's kvmclock, so we really have to follow the specification where

	 * it says that version is odd if data is being modified, and even after

	 * it is consistent.

	 *

	 * Version field updates must be kept separate.  This is because

	 * kvm_write_guest_cached might use a "rep movs" instruction, and

	 * writes within a string instruction are weakly ordered.  So there

	 * are three writes overall.

	 *

	 * As a small optimization, only write the version field in the first

	 * and third write.  The vcpu->pv_time cache is still valid, because the

	 * version field is the first in the struct.

	 */

	BUILD_BUG_ON(offsetof(struct pvclock_vcpu_time_info, version) != 0);



	vcpu->hv_clock.version = guest_hv_clock.version + 1;

	kvm_write_guest_cached(v->kvm, &vcpu->pv_time,

				&vcpu->hv_clock,

				sizeof(vcpu->hv_clock.version));



	smp_wmb();



	/* retain PVCLOCK_GUEST_STOPPED if set in guest copy */

	vcpu->hv_clock.flags |= (guest_hv_clock.flags & PVCLOCK_GUEST_STOPPED);



	if (vcpu->pvclock_set_guest_stopped_request) {

		vcpu->hv_clock.flags |= PVCLOCK_GUEST_STOPPED;

		vcpu->pvclock_set_guest_stopped_request = false;

	}



	trace_kvm_pvclock_update(v->vcpu_id, &vcpu->hv_clock);



	kvm_write_guest_cached(v->kvm, &vcpu->pv_time,

				&vcpu->hv_clock,

				sizeof(vcpu->hv_clock));



	smp_wmb();



	vcpu->hv_clock.version++;

	kvm_write_guest_cached(v->kvm, &vcpu->pv_time,

				&vcpu->hv_clock,

				sizeof(vcpu->hv_clock.version));

}



static int kvm_guest_time_update(struct kvm_vcpu *v)

{

	unsigned long flags, tgt_tsc_khz;
@@ -1729,7 +1783,6 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) 
	struct kvm_arch *ka = &v->kvm->arch;

	s64 kernel_ns;

	u64 tsc_timestamp, host_tsc;

	struct pvclock_vcpu_time_info guest_hv_clock;

	u8 pvclock_flags;

	bool use_master_clock;
@@ -1783,8 +1836,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) 


	local_irq_restore(flags);



	if (!vcpu->pv_time_enabled)

		return 0;

	/* With all the info we got, fill in the values */



	if (kvm_has_tsc_control)

		tgt_tsc_khz = kvm_scale_tsc(v, tgt_tsc_khz);
@@ -1796,64 +1848,21 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) 
		vcpu->hw_tsc_khz = tgt_tsc_khz;

	}



	/* With all the info we got, fill in the values */

	vcpu->hv_clock.tsc_timestamp = tsc_timestamp;

	vcpu->hv_clock.system_time = kernel_ns + v->kvm->arch.kvmclock_offset;

	vcpu->last_guest_tsc = tsc_timestamp;



	if (unlikely(kvm_read_guest_cached(v->kvm, &vcpu->pv_time,

		&guest_hv_clock, sizeof(guest_hv_clock))))

		return 0;



	/* This VCPU is paused, but it's legal for a guest to read another

	 * VCPU's kvmclock, so we really have to follow the specification where

	 * it says that version is odd if data is being modified, and even after

	 * it is consistent.

	 *

	 * Version field updates must be kept separate.  This is because

	 * kvm_write_guest_cached might use a "rep movs" instruction, and

	 * writes within a string instruction are weakly ordered.  So there

	 * are three writes overall.

	 *

	 * As a small optimization, only write the version field in the first

	 * and third write.  The vcpu->pv_time cache is still valid, because the

	 * version field is the first in the struct.

	 */

	BUILD_BUG_ON(offsetof(struct pvclock_vcpu_time_info, version) != 0);



	vcpu->hv_clock.version = guest_hv_clock.version + 1;

	kvm_write_guest_cached(v->kvm, &vcpu->pv_time,

				&vcpu->hv_clock,

				sizeof(vcpu->hv_clock.version));



	smp_wmb();



	/* retain PVCLOCK_GUEST_STOPPED if set in guest copy */

	pvclock_flags = (guest_hv_clock.flags & PVCLOCK_GUEST_STOPPED);



	if (vcpu->pvclock_set_guest_stopped_request) {

		pvclock_flags |= PVCLOCK_GUEST_STOPPED;

		vcpu->pvclock_set_guest_stopped_request = false;

	}



	/* If the host uses TSC clocksource, then it is stable */

	pvclock_flags = 0;

	if (use_master_clock)

		pvclock_flags |= PVCLOCK_TSC_STABLE_BIT;



	vcpu->hv_clock.flags = pvclock_flags;



	trace_kvm_pvclock_update(v->vcpu_id, &vcpu->hv_clock);



	kvm_write_guest_cached(v->kvm, &vcpu->pv_time,

				&vcpu->hv_clock,

				sizeof(vcpu->hv_clock));



	smp_wmb();

	if (!vcpu->pv_time_enabled)

		return 0;



	vcpu->hv_clock.version++;

	kvm_write_guest_cached(v->kvm, &vcpu->pv_time,

				&vcpu->hv_clock,

				sizeof(vcpu->hv_clock.version));

	kvm_setup_pvclock_page(v);

	return 0;

}