linux-kernel - Re: [PATCH RFC 2/3] x86/kvm/hyper-v: move VMX controls sanitization out of nested_enable

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Date:   Thu, 16 Jan 2020 01:30:43 +0200
From:   Liran Alon <liran.alon@...cle.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        linux-kernel@...r.kernel.org, Roman Kagan <rkagan@...tuozzo.com>
Subject: Re: [PATCH RFC 2/3] x86/kvm/hyper-v: move VMX controls sanitization
 out of nested_enable_evmcs()



> On 16 Jan 2020, at 1:27, Sean Christopherson <sean.j.christopherson@...el.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.

-Liran