[PATCH RFC: kvm tsc virtualization 18/20] Implement variable speed TSC

Zachary Amsden
2009-12-15T04:08:49Z

Add ioctl's to get and set TSC rate per-VM. The TSC rate is set at
creation to the reference tsc rate.

Signed-off-by: Zachary Amsden <zamsden@redhat.com>
---
arch/x86/include/asm/kvm_host.h | 4 +++
arch/x86/kvm/kvm_timer.h | 14 +---------
arch/x86/kvm/x86.c | 49 +++++++++++++++++++++++++++++++++++++++
include/linux/kvm.h | 3 ++
4 files changed, 58 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 8e4d606..313befc 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -276,6 +276,7 @@ struct kvm_mmu {
struct kvm_vcpu_arch {
u64 host_tsc;
u64 tsc_msr_offset;
+
/*
* rip and regs accesses must go through
* kvm_{register,rip}_{read,write} functions.
@@ -417,6 +418,9 @@ struct kvm_arch{
unsigned long irq_sources_bitmap;
u64 vm_init_tsc;
s64 kvmclock_offset;
+ unsigned int tsc_khz;
+ unsigned long tsc_multiplier;
+ int tsc_shift;

struct kvm_xen_hvm_config xen_hvm_config;
};
diff --git a/arch/x86/kvm/kvm_timer.h b/arch/x86/kvm/kvm_timer.h
index 3863161..670be31 100644
--- a/arch/x86/kvm/kvm_timer.h
+++ b/arch/x86/kvm/kvm_timer.h
@@ -23,15 +23,5 @@ static inline u64 kvm_get_elapsed_tsc(struct kvm *kvm)
return kvm_get_ref_tsc() - kvm->arch.vm_init_tsc;
}

-static inline u64 kvm_get_cpu_tsc(struct kvm_vcpu *vcpu)
-{
- return kvm_get_elapsed_tsc(vcpu->kvm) + vcpu->arch.tsc_msr_offset;
-}
-
-static inline void kvm_set_cpu_tsc(struct kvm_vcpu *vcpu, u64 data)
-{
- u64 tsc_offset;
-
- tsc_offset = data - kvm_get_cpu_tsc(vcpu);
- vcpu->arch.tsc_msr_offset = tsc_offset;
-}
+extern u64 kvm_get_cpu_tsc(struct kvm_vcpu *vcpu);
+extern void kvm_set_cpu_tsc(struct kvm_vcpu *vcpu, u64 data);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3a854ec..c1bed03 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1727,6 +1727,7 @@ int kvm_dev_ioctl_check_extension(long ext)
case KVM_CAP_SET_IDENTITY_MAP_ADDR:
case KVM_CAP_XEN_HVM:
case KVM_CAP_ADJUST_CLOCK:
+ case KVM_CAP_SET_TSC_RATE:
r = 1;
break;
case KVM_CAP_COALESCED_MMIO:
@@ -2680,6 +2681,34 @@ out:
return r;
}

+u64 kvm_get_cpu_tsc(struct kvm_vcpu *vcpu)
+{
+ u64 tsc;
+ struct kvm *kvm = vcpu->kvm;
+
+ tsc = kvm_get_elapsed_tsc(kvm) + vcpu->arch.tsc_msr_offset;
+ tsc = mult_precise(tsc, kvm->arch.tsc_multiplier, kvm->arch.tsc_shift);
+ return tsc;
+}
+EXPORT_SYMBOL_GPL(kvm_get_cpu_tsc);
+
+void kvm_set_cpu_tsc(struct kvm_vcpu *vcpu, u64 data)
+{
+ u64 tsc_offset;
+
+ tsc_offset = data - kvm_get_cpu_tsc(vcpu);
+ vcpu->arch.tsc_msr_offset = tsc_offset;
+}
+EXPORT_SYMBOL_GPL(kvm_set_cpu_tsc);
+
+static int kvm_set_tsc_rate(struct kvm *kvm, u32 new_tsc_khz)
+{
+ kvm->arch.tsc_khz = new_tsc_khz;
+ compute_best_multiplier(new_tsc_khz, ref_tsc_khz,
+ &kvm->arch.tsc_multiplier, &kvm->arch.tsc_shift);
+ return 0;
+}
+
long kvm_arch_vm_ioctl(struct file *filp,
unsigned int ioctl, unsigned long arg)
{
@@ -2986,6 +3015,25 @@ long kvm_arch_vm_ioctl(struct file *filp,

break;
}
+ case KVM_X86_GET_TSC_RATE: {
+ u32 rate = kvm->arch.tsc_khz;
+ r = -EFAULT;
+ if (copy_to_user(argp, &rate, sizeof(rate)))
+ goto out;
+ r = 0;
+ break;
+ }
+ case KVM_X86_SET_TSC_RATE: {
+ u32 tsc_rate;
+ r = -EFAULT;
+ if (copy_from_user(&tsc_rate, argp, sizeof tsc_rate))
+ goto out;
+ r = -EINVAL;
+ if (tsc_rate == 0 || tsc_rate > (1ULL << 30))
+ goto out;
+ r = kvm_set_tsc_rate(kvm, tsc_rate);
+ break;
+ }

default:
;
@@ -5611,6 +5659,7 @@ struct kvm *kvm_arch_create_vm(void)
set_bit(KVM_USERSPACE_IRQ_SOURCE_ID, &kvm->arch.irq_sources_bitmap);

kvm->arch.vm_init_tsc = kvm_get_ref_tsc();
+ kvm_set_tsc_rate(kvm, ref_tsc_khz);

return kvm;
}
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 6ed1a12..ac2f0af 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -440,6 +440,7 @@ struct kvm_ioeventfd {
#define KVM_CAP_XEN_HVM 38
#endif
#define KVM_CAP_ADJUST_CLOCK 39
+#define KVM_CAP_SET_TSC_RATE 40

#ifdef KVM_CAP_IRQ_ROUTING

@@ -619,6 +620,8 @@ struct kvm_clock_data {
#define KVM_X86_SETUP_MCE _IOW(KVMIO, 0x9c, __u64)
#define KVM_X86_GET_MCE_CAP_SUPPORTED _IOR(KVMIO, 0x9d, __u64)
#define KVM_X86_SET_MCE _IOW(KVMIO, 0x9e, struct kvm_x86_mce)
+#define KVM_X86_GET_TSC_RATE _IOR(KVMIO, 0x9f, __u64)
+#define KVM_X86_SET_TSC_RATE _IOW(KVMIO, 0xa0, __u64)

/*
* Deprecated interfaces
--
1.6.5.2