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: Roman Kagan <rkagan@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b4ae925..d1e8307 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -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;
 }