Add an IOCTL for setting the TSC rate for a VM, intended to
be used to migrate non-kvmclock based VMs which rely on TSC
rate staying stable across host migration.
Signed-off-by: Zachary Amsden <zamsden@xxxxxxxxxx>
---
arch/x86/kvm/x86.c | 36 ++++++++++++++++++++++++++++++++++++
include/linux/kvm.h | 4 ++++
2 files changed, 40 insertions(+), 0 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 887e30f..e618265 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1017,6 +1017,10 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
kvm_x86_ops->adjust_tsc_offset(v, tsc-tsc_timestamp);
local_irq_restore(flags);
+ /* hw_tsc_khz unknown at creation time, check for overrun */
+ if (this_tsc_khz > v->kvm->arch.virtual_tsc_khz)
+ vcpu->tsc_overrun = 1;
+
/* Now, see if we need to switch into trap mode */
if (vcpu->tsc_overrun && !vcpu->tsc_trapping)
kvm_x86_ops->set_tsc_trap(v, 1);
@@ -1846,6 +1850,7 @@ int kvm_dev_ioctl_check_extension(long ext)
case KVM_CAP_DEBUGREGS:
case KVM_CAP_X86_ROBUST_SINGLESTEP:
case KVM_CAP_XSAVE:
+ case KVM_CAP_SET_TSC_RATE:
r = 1;
break;
case KVM_CAP_COALESCED_MMIO:
@@ -3413,6 +3418,37 @@ long kvm_arch_vm_ioctl(struct file *filp,
r = 0;
break;
}
+ case KVM_X86_GET_TSC_RATE: {
+ u32 rate = kvm->arch.virtual_tsc_khz;
+ r = -EFAULT;
+ if (copy_to_user(argp, &rate, sizeof(rate)))
+ goto out;
+ r = 0;
+ break;
+ }
+ case KVM_X86_SET_TSC_RATE: {
+ u32 rate;
+ int i;
+ struct kvm_vcpu *vcpu;
+ r = -EFAULT;
+ if (copy_from_user(&rate, argp, sizeof rate))
+ goto out;
+ if (rate == 0 || rate > (1ULL << 40)) {
+ r = -EINVAL;
+ break;
+ }
+ /*
+ * This is intended to be called once, during VM creation.
+ * Calling this with running VCPUs to dynamically change
+ * speed is risky; there is no synchronization with the
+ * compensation loop, so computations using virtual_tsc_khz
+ * conversions may go haywire. Use at your own risk.
+ */
+ kvm_arch_set_tsc_khz(kvm, rate);
+ kvm_for_each_vcpu(i, vcpu, kvm)
+ kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
+ break;
+ }
default:
;
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 3707704..22d27f2 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -539,6 +539,7 @@ struct kvm_ppc_pvinfo {
#define KVM_CAP_XCRS 56
#endif
#define KVM_CAP_PPC_GET_PVINFO 57
+#define KVM_CAP_SET_TSC_RATE 58
#ifdef KVM_CAP_IRQ_ROUTING
@@ -675,6 +676,9 @@ struct kvm_clock_data {
#define KVM_SET_PIT2 _IOW(KVMIO, 0xa0, struct kvm_pit_state2)
/* Available with KVM_CAP_PPC_GET_PVINFO */
#define KVM_PPC_GET_PVINFO _IOW(KVMIO, 0xa1, struct kvm_ppc_pvinfo)
+/* Available with KVM_CAP_SET_TSC_RATE */
+#define KVM_X86_GET_TSC_RATE _IOR(KVMIO, 0xa2, __u32)
+#define KVM_X86_SET_TSC_RATE _IOW(KVMIO, 0xa3, __u32)
/*
* ioctls for vcpu fds
--
1.7.1
--
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