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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 09:51:47 +0100
Message-ID: <877e1riy1o.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <C6C4003E-0ADD-42A5-A580-09E06806E160@oracle.com>

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()).

-- 
Vitaly


  reply index

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 [this message]
2020-01-16 16:19         ` Sean Christopherson
2020-01-16 16:57           ` Vitaly Kuznetsov
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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