On Tue, Jan 14, 2014 at 08:22:17PM +1100, Vadim Rozenfeld wrote:
> The following patch allows to activate a partition reference
> time enlightenment that is based on the host platform's support
> for an Invariant Time Stamp Counter (iTSC).
>
> v2 -> v3
> Handle TSC sequence, scale, and offest changing during migration.
>
> v3 -> v4
> 1. Wrap access to iTSC page with kvm_read_guest/kvm_write_guest
> suggested by Andrew Honig <ahonig@xxxxxxxxxx> and Marcelo
> 2. iTSC data calculation/access fixes suggested by Marcelo and Paolo
>
> ---
> arch/x86/kvm/x86.c | 29 +++++++++++++++++++++++++++++
> 1 file changed, 29 insertions(+)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 496bdb1..6e6debf 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1873,6 +1873,7 @@ static int set_msr_hyperv_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data)
> case HV_X64_MSR_REFERENCE_TSC: {
> u64 gfn;
> unsigned long addr;
> + struct kvm_arch *ka = &kvm->arch;
> HV_REFERENCE_TSC_PAGE tsc_ref;
> memset(&tsc_ref, 0, sizeof(tsc_ref));
> if (!(data & HV_X64_MSR_TSC_REFERENCE_ENABLE)) {
> @@ -1883,6 +1884,13 @@ static int set_msr_hyperv_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data)
> addr = gfn_to_hva(kvm, gfn);
> if (kvm_is_error_hva(addr))
> return 1;
> + if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC)
> + && ka->use_master_clock) {
> + tsc_ref.tsc_sequence = 1;
> + tsc_ref.tsc_scale = ((10000LL << 32) /
> + vcpu->arch.virtual_tsc_khz) << 32;
> + tsc_ref.tsc_offset = kvm->arch.kvmclock_offset;
> + }
> if (__copy_to_user((void __user *)addr, &tsc_ref, sizeof(tsc_ref)))
> return 1;
> mark_page_dirty(kvm, gfn);
> @@ -3871,6 +3879,27 @@ long kvm_arch_vm_ioctl(struct file *filp,
> local_irq_enable();
> kvm->arch.kvmclock_offset = delta;
> kvm_gen_update_masterclock(kvm);
> + if (kvm->arch.hv_tsc_page & HV_X64_MSR_TSC_REFERENCE_ENABLE) {
> + HV_REFERENCE_TSC_PAGE tsc_ref;
> + struct kvm_arch *ka = &kvm->arch;
> + r = kvm_read_guest(kvm, kvm->arch.hv_tsc_page,
> + &tsc_ref, sizeof(tsc_ref));
> + if (r)
> + goto out;
> + if (tsc_ref.tsc_sequence
> + && boot_cpu_has(X86_FEATURE_CONSTANT_TSC)
> + && ka->use_master_clock) {
> + tsc_ref.tsc_sequence++;
> + tsc_ref.tsc_scale = ((10000LL << 32) /
> + __get_cpu_var(cpu_tsc_khz)) << 32;
> + tsc_ref.tsc_offset = kvm->arch.kvmclock_offset;
> + } else
> + tsc_ref.tsc_sequence = 0;
> + r = kvm_write_guest(kvm, kvm->arch.hv_tsc_page,
> + &tsc_ref, sizeof(tsc_ref));
> + if (r)
> + goto out;
> + }
> break;
> }
Vadim,
A short comment explaining the lifecycle of the exposed
clock would be nice.
Can you explain why are you setting tsc_offset to kvmclock_offset?
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