diff options
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/kvm/hyperv.c | 26 |
1 files changed, 25 insertions, 1 deletions
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index 5c0f10a2b3ab..f98370a39936 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -1077,6 +1077,21 @@ static bool compute_tsc_page_parameters(struct pvclock_vcpu_time_info *hv_clock, return true; } +/* + * Don't touch TSC page values if the guest has opted for TSC emulation after + * migration. KVM doesn't fully support reenlightenment notifications and TSC + * access emulation and Hyper-V is known to expect the values in TSC page to + * stay constant before TSC access emulation is disabled from guest side + * (HV_X64_MSR_TSC_EMULATION_STATUS). KVM userspace is expected to preserve TSC + * frequency and guest visible TSC value across migration (and prevent it when + * TSC scaling is unsupported). + */ +static inline bool tsc_page_update_unsafe(struct kvm_hv *hv) +{ + return (hv->hv_tsc_page_status != HV_TSC_PAGE_GUEST_CHANGED) && + hv->hv_tsc_emulation_control; +} + void kvm_hv_setup_tsc_page(struct kvm *kvm, struct pvclock_vcpu_time_info *hv_clock) { @@ -1104,6 +1119,14 @@ void kvm_hv_setup_tsc_page(struct kvm *kvm, &tsc_seq, sizeof(tsc_seq)))) goto out_err; + if (tsc_seq && tsc_page_update_unsafe(hv)) { + if (kvm_read_guest(kvm, gfn_to_gpa(gfn), &hv->tsc_ref, sizeof(hv->tsc_ref))) + goto out_err; + + hv->hv_tsc_page_status = HV_TSC_PAGE_SET; + goto out_unlock; + } + /* * While we're computing and writing the parameters, force the * guest to use the time reference count MSR. @@ -1151,7 +1174,8 @@ void kvm_hv_invalidate_tsc_page(struct kvm *kvm) u64 gfn; if (hv->hv_tsc_page_status == HV_TSC_PAGE_BROKEN || - hv->hv_tsc_page_status == HV_TSC_PAGE_UNSET) + hv->hv_tsc_page_status == HV_TSC_PAGE_UNSET || + tsc_page_update_unsafe(hv)) return; mutex_lock(&hv->hv_lock); |