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

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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>
This commit is contained in:
Paolo Bonzini 2016-09-01 14:20:09 +02:00
parent 4f5758fc67
commit 0d6dd2ff82
1 changed files with 59 additions and 50 deletions
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109
arch/x86/kvm/x86.c
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@ -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);
if (!vcpu->pv_time_enabled)
return 0;
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));
kvm_setup_pvclock_page(v);
return 0;
}