From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Liran Alon <liran.alon@oracle.com>,
kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
Jim Mattson <jmattson@google.com>,
linux-kernel@vger.kernel.org, Roman Kagan <rkagan@virtuozzo.com>
Subject: Re: [PATCH RFC 2/3] x86/kvm/hyper-v: move VMX controls sanitization out of nested_enable_evmcs()
Date: Thu, 16 Jan 2020 17:57:31 +0100 [thread overview]
Message-ID: <87o8v3gwzo.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <20200116161928.GC20561@linux.intel.com>
Sean Christopherson <sean.j.christopherson@intel.com> writes:
> On Thu, Jan 16, 2020 at 09:51:47AM +0100, Vitaly Kuznetsov wrote:
>> Liran Alon <liran.alon@oracle.com> writes:
>>
>> >> On 16 Jan 2020, at 1:27, Sean Christopherson <sean.j.christopherson@intel.com> 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]));
>
I accuse you of not reading my PATCH0 :-)
https://lists.nongnu.org/archive/html/qemu-devel/2020-01/msg00123.html
does exactly this :-)
P.S. I expect Paolo to comment on which hack he hates less :-)
--
Vitaly
next prev parent reply other threads:[~2020-01-16 16:58 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-15 17:10 [PATCH RFC 0/3] x86/kvm/hyper-v: fix enlightened VMCS & QEMU4.2 Vitaly Kuznetsov
2020-01-15 17:10 ` [PATCH RFC 1/3] x86/kvm/hyper-v: remove stale evmcs_already_enabled check from nested_enable_evmcs() Vitaly Kuznetsov
2020-01-15 22:50 ` Liran Alon
2020-01-15 17:10 ` [PATCH RFC 2/3] x86/kvm/hyper-v: move VMX controls sanitization out of nested_enable_evmcs() Vitaly Kuznetsov
2020-01-15 22:49 ` Liran Alon
2020-01-16 8:37 ` Vitaly Kuznetsov
2020-02-03 15:11 ` Vitaly Kuznetsov
2020-01-15 23:27 ` Sean Christopherson
2020-01-15 23:30 ` Liran Alon
2020-01-16 8:51 ` Vitaly Kuznetsov
2020-01-16 16:19 ` Sean Christopherson
2020-01-16 16:57 ` Vitaly Kuznetsov [this message]
2020-01-17 6:31 ` Sean Christopherson
2020-01-18 21:42 ` Paolo Bonzini
2020-01-19 8:54 ` Paolo Bonzini
2020-01-22 5:47 ` Sean Christopherson
2020-01-22 9:37 ` Vitaly Kuznetsov
2020-01-22 14:33 ` Paolo Bonzini
2020-01-22 15:08 ` Vitaly Kuznetsov
2020-01-22 15:51 ` Sean Christopherson
2020-01-22 16:29 ` Vitaly Kuznetsov
2020-01-22 16:40 ` Paolo Bonzini
2020-01-23 9:15 ` Vitaly Kuznetsov
2020-01-23 19:09 ` Vitaly Kuznetsov
2020-01-24 17:25 ` Sean Christopherson
2020-01-27 15:38 ` Vitaly Kuznetsov
2020-01-27 17:53 ` Paolo Bonzini
2020-01-27 21:52 ` Vitaly Kuznetsov
2020-01-27 18:17 ` Sean Christopherson
2020-01-15 17:10 ` [PATCH RFC 3/3] x86/kvm/hyper-v: don't allow to turn on unsupported VMX controls for nested guests Vitaly Kuznetsov
2020-01-15 22:59 ` Liran Alon
2020-01-16 8:55 ` Vitaly Kuznetsov
2020-01-16 16:21 ` Sean Christopherson
2020-01-19 8:57 ` Paolo Bonzini
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