diff options
| -rw-r--r-- | docs/system/i386/hyperv.rst | 13 | ||||
| -rw-r--r-- | target/i386/kvm/kvm.c | 7 |
2 files changed, 14 insertions, 6 deletions
diff --git a/docs/system/i386/hyperv.rst b/docs/system/i386/hyperv.rst index 2505dc4c86..009947e391 100644 --- a/docs/system/i386/hyperv.rst +++ b/docs/system/i386/hyperv.rst @@ -262,14 +262,19 @@ Supplementary features ``hv-passthrough`` In some cases (e.g. during development) it may make sense to use QEMU in 'pass-through' mode and give Windows guests all enlightenments currently - supported by KVM. This pass-through mode is enabled by "hv-passthrough" CPU - flag. + supported by KVM. Note: ``hv-passthrough`` flag only enables enlightenments which are known to QEMU (have corresponding 'hv-' flag) and copies ``hv-spinlocks`` and ``hv-vendor-id`` values from KVM to QEMU. ``hv-passthrough`` overrides all other 'hv-' settings on - the command line. Also, enabling this flag effectively prevents migration as the - list of enabled enlightenments may differ between target and destination hosts. + the command line. + + Note: ``hv-passthrough`` does not enable ``hv-syndbg`` which can prevent certain + Windows guests from booting when used without proper configuration. If needed, + ``hv-syndbg`` can be enabled additionally. + + Note: ``hv-passthrough`` effectively prevents migration as the list of enabled + enlightenments may differ between target and destination hosts. ``hv-enforce-cpuid`` By default, KVM allows the guest to use all currently supported Hyper-V diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c index 1ec4977a8e..fd9f198892 100644 --- a/target/i386/kvm/kvm.c +++ b/target/i386/kvm/kvm.c @@ -934,6 +934,7 @@ static struct { uint32_t bits; } flags[2]; uint64_t dependencies; + bool skip_passthrough; } kvm_hyperv_properties[] = { [HYPERV_FEAT_RELAXED] = { .desc = "relaxed timing (hv-relaxed)", @@ -1062,7 +1063,8 @@ static struct { {.func = HV_CPUID_FEATURES, .reg = R_EDX, .bits = HV_FEATURE_DEBUG_MSRS_AVAILABLE} }, - .dependencies = BIT(HYPERV_FEAT_SYNIC) | BIT(HYPERV_FEAT_RELAXED) + .dependencies = BIT(HYPERV_FEAT_SYNIC) | BIT(HYPERV_FEAT_RELAXED), + .skip_passthrough = true, }, [HYPERV_FEAT_MSR_BITMAP] = { .desc = "enlightened MSR-Bitmap (hv-emsr-bitmap)", @@ -1471,7 +1473,8 @@ bool kvm_hyperv_expand_features(X86CPU *cpu, Error **errp) * hv_build_cpuid_leaf() uses this info to build guest CPUIDs. */ for (feat = 0; feat < ARRAY_SIZE(kvm_hyperv_properties); feat++) { - if (hyperv_feature_supported(cs, feat)) { + if (hyperv_feature_supported(cs, feat) && + !kvm_hyperv_properties[feat].skip_passthrough) { cpu->hyperv_features |= BIT(feat); } } |