On Thu, Jan 16, 2020 at 09:51:47AM +0100, Vitaly Kuznetsov wrote: > Liran Alon <liran.alon@xxxxxxxxxx> writes: > > >> On 16 Jan 2020, at 1:27, Sean Christopherson <sean.j.christopherson@xxxxxxxxx> wrote: > >> > >> On Wed, Jan 15, 2020 at 06:10:13PM +0100, Vitaly Kuznetsov wrote: > >>> With fine grained VMX feature enablement QEMU>=4.2 tries to do KVM_SET_MSRS > >>> with default (matching CPU model) values and in case eVMCS is also enabled, > >>> fails. > >> > >> As in, Qemu is blindly throwing values at KVM and complains on failure? > >> That seems like a Qemu bug, especially since Qemu needs to explicitly do > >> KVM_CAP_HYPERV_ENLIGHTENED_VMCS to enable eVMCS. > > > > See: https://patchwork.kernel.org/patch/11316021/ > > For more context. > > Ya, > > while it would certainly be possible to require that userspace takes > into account KVM_CAP_HYPERV_ENLIGHTENED_VMCS (which is an opt-in) when > doing KVM_SET_MSRS there doesn't seem to be an existing (easy) way to > figure out which VMX controls were filtered out after enabling > KVM_CAP_HYPERV_ENLIGHTENED_VMCS: KVM_GET_MSRS returns global > &vmcs_config.nested values for VMX MSRs (vmx_get_msr_feature()). Ah, I was looking at the call to vmx_get_vmx_msr(&vmx->nested.msrs, ...) in vmx_get_msr(). Why not just do this in Qemu? IMO that's not a major ask, e.g. Qemu is doing a decent amount of manual adjustment anyways. And Qemu isn't even using the result of KVM_GET_MSRS so I don't think it's fair to say this is solely KVM's fault. diff --git a/target/i386/kvm.c b/target/i386/kvm.c index 1d10046a6c..6545bb323e 100644 --- a/target/i386/kvm.c +++ b/target/i386/kvm.c @@ -2623,6 +2623,23 @@ static void kvm_msr_entry_add_vmx(X86CPU *cpu, FeatureWordArray f) MSR_VMX_EPT_UC | MSR_VMX_EPT_WB : 0); uint64_t fixed_vmx_ept_vpid = kvm_vmx_ept_vpid & fixed_vmx_ept_mask; + /* Hyper-V's eVMCS does't support certain features, adjust accordingly. */ + if (cpu->hyperv_evmcs) { + f[FEAT_VMX_PINBASED_CTLS] &= ~(VMX_PIN_BASED_VMX_PREEMPTION_TIMER | + VMX_PIN_BASED_POSTED_INTR); + f[FEAT_VMX_EXIT_CTLS] &= ~VMX_VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL; + f[FEAT_VMX_ENTRY_CTLS] &= ~VMX_VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL; + f[FEAT_VMX_SECONDARY_CTLS] &= ~(VMX_SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY | + VMX_SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES | + VMX_SECONDARY_EXEC_APIC_REGISTER_VIRT | + VMX_SECONDARY_EXEC_ENABLE_PML | + VMX_SECONDARY_EXEC_ENABLE_VMFUNC | + VMX_SECONDARY_EXEC_SHADOW_VMCS | + /* VMX_SECONDARY_EXEC_TSC_SCALING | */ + VMX_SECONDARY_EXEC_PAUSE_LOOP_EXITING); + f[FEAT_VMX_VMFUNC] &= ~MSR_VMX_VMFUNC_EPT_SWITCHING; + } + kvm_msr_entry_add(cpu, MSR_IA32_VMX_TRUE_PROCBASED_CTLS, make_vmx_msr_value(MSR_IA32_VMX_TRUE_PROCBASED_CTLS, f[FEAT_VMX_PROCBASED_CTLS]));
