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Message-Id: <1474285153-4216-2-git-send-email-pbonzini@redhat.com>
Date: Mon, 19 Sep 2016 13:39:10 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc: rkrcmar@...hat.com, den@...nvz.org, rkagan@...tuozzo.com,
peterhornyack@...gle.com
Subject: [PATCH 1/4] 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.
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
arch/x86/kvm/x86.c | 109 +++++++++++++++++++++++++++++------------------------
1 file changed, 59 insertions(+), 50 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b4ae92599d34..d1e830715e40 100644
--- 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;
}
--
1.8.3.1
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