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SubjectRe: [KVM timekeeping 30/35] IOCTL for setting TSC rate
On Thu, Aug 19, 2010 at 10:07:44PM -1000, Zachary Amsden wrote:
> 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@redhat.com>
> ---
> 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)

wrap this into a struct?



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