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Date: Tue, 28 Dec 2010 19:38:19 -1000
From: Zachary Amsden <zamsden@...hat.com>
To: kvm@...r.kernel.org
Cc: Zachary Amsden <zamsden@...hat.com>, Avi Kivity <avi@...hat.com>,
Marcelo Tosatti <mtosatti@...hat.com>,
Glauber Costa <glommer@...hat.com>,
linux-kernel@...r.kernel.org
Subject: [KVM Clock Synchronization 3/4] Refactor KVM clock update code
Refactor this to make upcoming steps easier to follow.
This should be 100% code motion and renaming.
Signed-off-by: Zachary Amsden <zamsden@...hat.com>
---
arch/x86/include/asm/kvm_host.h | 2 +-
arch/x86/kvm/x86.c | 77 +++++++++++++++++++++++----------------
2 files changed, 46 insertions(+), 33 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 63a82b0..8d829b8 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -444,7 +444,7 @@ struct kvm_arch {
unsigned long irq_sources_bitmap;
s64 kvmclock_offset;
- spinlock_t tsc_write_lock;
+ spinlock_t clock_lock;
u64 last_tsc_nsec;
u64 last_tsc_offset;
u64 last_tsc_write;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b509c01..59d5999 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -996,7 +996,7 @@ void kvm_write_tsc(struct kvm_vcpu *vcpu, u64 data)
s64 sdiff;
u64 delta;
- spin_lock_irqsave(&kvm->arch.tsc_write_lock, flags);
+ spin_lock_irqsave(&kvm->arch.clock_lock, flags);
offset = data - native_read_tsc();
ns = get_kernel_ns();
elapsed = ns - kvm->arch.last_tsc_nsec;
@@ -1034,7 +1034,7 @@ void kvm_write_tsc(struct kvm_vcpu *vcpu, u64 data)
kvm->arch.last_tsc_offset = offset;
}
kvm_x86_ops->write_tsc_offset(vcpu, offset);
- spin_unlock_irqrestore(&kvm->arch.tsc_write_lock, flags);
+ spin_unlock_irqrestore(&kvm->arch.clock_lock, flags);
/* Reset of TSC must disable overshoot protection below */
vcpu->arch.hv_clock.tsc_timestamp = 0;
@@ -1043,22 +1043,50 @@ void kvm_write_tsc(struct kvm_vcpu *vcpu, u64 data)
}
EXPORT_SYMBOL_GPL(kvm_write_tsc);
+static void update_pvclock(struct kvm_vcpu *v,
+ struct pvclock_vcpu_time_info *pvclock,
+ u64 tsc_timestamp,
+ s64 kernel_ns,
+ unsigned long tsc_khz)
+{
+ if (unlikely(v->arch.hw_tsc_khz != tsc_khz)) {
+ kvm_get_time_scale(NSEC_PER_SEC / 1000, tsc_khz,
+ &pvclock->tsc_shift,
+ &pvclock->tsc_to_system_mul);
+ v->arch.hw_tsc_khz = tsc_khz;
+ }
+ pvclock->tsc_timestamp = tsc_timestamp;
+ pvclock->system_time = kernel_ns + v->kvm->arch.kvmclock_offset;
+ pvclock->flags = 0;
+}
+
+static void update_user_kvmclock(struct kvm_vcpu *v,
+ struct pvclock_vcpu_time_info *pvclock)
+{
+ struct kvm_vcpu_arch *vcpu = &v->arch;
+ void *shared_kaddr;
+
+ shared_kaddr = kmap_atomic(vcpu->time_page, KM_USER0);
+ memcpy(shared_kaddr + vcpu->time_offset, pvclock, sizeof(*pvclock));
+ kunmap_atomic(shared_kaddr, KM_USER0);
+ mark_page_dirty(v->kvm, vcpu->time >> PAGE_SHIFT);
+}
+
static int kvm_guest_time_update(struct kvm_vcpu *v)
{
unsigned long flags;
struct kvm_vcpu_arch *vcpu = &v->arch;
- void *shared_kaddr;
- unsigned long this_tsc_khz;
- s64 kernel_ns, max_kernel_ns;
+ unsigned long tsc_khz;
+ s64 kernel_ns;
u64 tsc_timestamp;
/* Keep irq disabled to prevent changes to the clock */
local_irq_save(flags);
kvm_get_msr(v, MSR_IA32_TSC, &tsc_timestamp);
kernel_ns = get_kernel_ns();
- this_tsc_khz = __get_cpu_var(cpu_tsc_khz);
+ tsc_khz = __get_cpu_var(cpu_tsc_khz);
- if (unlikely(this_tsc_khz == 0)) {
+ if (unlikely(tsc_khz == 0)) {
local_irq_restore(flags);
kvm_make_request(KVM_REQ_CLOCK_UPDATE, v);
return 1;
@@ -1108,32 +1136,23 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
* guest. To protect against this, we must compute the system time as
* observed by the guest and ensure the new system time is greater.
*/
- max_kernel_ns = 0;
if (vcpu->hv_clock.tsc_timestamp && vcpu->last_guest_tsc) {
- max_kernel_ns = vcpu->last_guest_tsc -
- vcpu->hv_clock.tsc_timestamp;
+ s64 max_kernel_ns = vcpu->last_guest_tsc -
+ vcpu->hv_clock.tsc_timestamp;
max_kernel_ns = pvclock_scale_delta(max_kernel_ns,
vcpu->hv_clock.tsc_to_system_mul,
vcpu->hv_clock.tsc_shift);
max_kernel_ns += vcpu->last_kernel_ns;
+ if (max_kernel_ns > kernel_ns)
+ kernel_ns = max_kernel_ns;
}
- if (unlikely(vcpu->hw_tsc_khz != this_tsc_khz)) {
- kvm_get_time_scale(NSEC_PER_SEC / 1000, this_tsc_khz,
- &vcpu->hv_clock.tsc_shift,
- &vcpu->hv_clock.tsc_to_system_mul);
- vcpu->hw_tsc_khz = this_tsc_khz;
- }
-
- if (max_kernel_ns > kernel_ns)
- kernel_ns = max_kernel_ns;
-
- /* 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;
+ /* Record the last values observed for next time */
vcpu->last_kernel_ns = kernel_ns;
vcpu->last_guest_tsc = tsc_timestamp;
- vcpu->hv_clock.flags = 0;
+
+ /* Compute new clock values */
+ update_pvclock(v, &vcpu->hv_clock, tsc_timestamp, kernel_ns, tsc_khz);
/*
* The interface expects us to write an even number signaling that the
@@ -1142,14 +1161,8 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
*/
vcpu->hv_clock.version += 2;
- shared_kaddr = kmap_atomic(vcpu->time_page, KM_USER0);
-
- memcpy(shared_kaddr + vcpu->time_offset, &vcpu->hv_clock,
- sizeof(vcpu->hv_clock));
+ update_user_kvmclock(v, &vcpu->hv_clock);
- kunmap_atomic(shared_kaddr, KM_USER0);
-
- mark_page_dirty(v->kvm, vcpu->time >> PAGE_SHIFT);
return 0;
}
@@ -5951,7 +5964,7 @@ struct kvm *kvm_arch_create_vm(void)
/* Reserve bit 0 of irq_sources_bitmap for userspace irq source */
set_bit(KVM_USERSPACE_IRQ_SOURCE_ID, &kvm->arch.irq_sources_bitmap);
- spin_lock_init(&kvm->arch.tsc_write_lock);
+ spin_lock_init(&kvm->arch.clock_lock);
return kvm;
}
--
1.7.1
--
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