From da1cc323b8aee60d4816ce7521177b14ec3008b4 Mon Sep 17 00:00:00 2001 From: Evgeny Yakovlev Date: Wed, 22 Nov 2017 21:14:16 +0300 Subject: [PATCH] hyperv: set partition-wide MSRs only on first vcpu Hyper-V has a notion of partition-wide MSRs. Those MSRs are read and written as usual on each VCPU, however the hypervisor maintains a single global value for all VCPUs. Thus writing such an MSR from any single VCPU affects the global value that is read by all other VCPUs. This leads to an issue during VCPU hotplug: the zero-initialzied values of those MSRs get synced into KVM and override the global values as has already been set by the guest. This change makes the partition-wide MSRs only be synchronized on the first vcpu. Signed-off-by: Evgeny Yakovlev Signed-off-by: Roman Kagan Message-Id: <20171122181418.14180-2-rkagan@virtuozzo.com> Signed-off-by: Paolo Bonzini --- target/i386/cpu.h | 5 ++++- target/i386/kvm.c | 23 +++++++++++++++-------- 2 files changed, 19 insertions(+), 9 deletions(-) diff --git a/target/i386/cpu.h b/target/i386/cpu.h index cdbf8b0cd7..17f1bb7ecb 100644 --- a/target/i386/cpu.h +++ b/target/i386/cpu.h @@ -1097,10 +1097,13 @@ typedef struct CPUX86State { uint64_t async_pf_en_msr; uint64_t pv_eoi_en_msr; + /* Partition-wide HV MSRs, will be updated only on the first vcpu */ uint64_t msr_hv_hypercall; uint64_t msr_hv_guest_os_id; - uint64_t msr_hv_vapic; uint64_t msr_hv_tsc; + + /* Per-VCPU HV MSRs */ + uint64_t msr_hv_vapic; uint64_t msr_hv_crash_params[HV_CRASH_PARAMS]; uint64_t msr_hv_runtime; uint64_t msr_hv_synic_control; diff --git a/target/i386/kvm.c b/target/i386/kvm.c index d4b2ce2e94..89fa65e243 100644 --- a/target/i386/kvm.c +++ b/target/i386/kvm.c @@ -1678,19 +1678,26 @@ static int kvm_put_msrs(X86CPU *cpu, int level) kvm_msr_entry_add(cpu, MSR_CORE_PERF_GLOBAL_CTRL, env->msr_global_ctrl); } - if (has_msr_hv_hypercall) { - kvm_msr_entry_add(cpu, HV_X64_MSR_GUEST_OS_ID, - env->msr_hv_guest_os_id); - kvm_msr_entry_add(cpu, HV_X64_MSR_HYPERCALL, - env->msr_hv_hypercall); + /* + * Hyper-V partition-wide MSRs: to avoid clearing them on cpu hot-add, + * only sync them to KVM on the first cpu + */ + if (current_cpu == first_cpu) { + if (has_msr_hv_hypercall) { + kvm_msr_entry_add(cpu, HV_X64_MSR_GUEST_OS_ID, + env->msr_hv_guest_os_id); + kvm_msr_entry_add(cpu, HV_X64_MSR_HYPERCALL, + env->msr_hv_hypercall); + } + if (cpu->hyperv_time) { + kvm_msr_entry_add(cpu, HV_X64_MSR_REFERENCE_TSC, + env->msr_hv_tsc); + } } if (cpu->hyperv_vapic) { kvm_msr_entry_add(cpu, HV_X64_MSR_APIC_ASSIST_PAGE, env->msr_hv_vapic); } - if (cpu->hyperv_time) { - kvm_msr_entry_add(cpu, HV_X64_MSR_REFERENCE_TSC, env->msr_hv_tsc); - } if (has_msr_hv_crash) { int j; -- 2.11.0