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From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
	kvm@vger.kernel.org, Jim Mattson <jmattson@google.com>,
	linux-kernel@vger.kernel.org, Liran Alon <liran.alon@oracle.com>,
	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: Wed, 22 Jan 2020 15:33:05 +0100
Message-ID: <9c126d75-225b-3b1b-d97a-bcec1f189e02@redhat.com> (raw)
In-Reply-To: <20200122054724.GD18513@linux.intel.com>

On 22/01/20 06:47, Sean Christopherson wrote:
>> Yes, it most likely is and it would be nice if Microsoft fixed it, but I
>> guess we're stuck with it for existing Windows versions.  Well, for one
>> we found a bug in Hyper-V and not the converse. :)
>>
>> There is a problem with this approach, in that we're stuck with it
>> forever due to live migration.  But I guess if in the future eVMCS v2
>> adds an apic_address field we can limit the hack to eVMCS v1.  Another
>> possibility is to use the quirks mechanism but it's overkill for now.
>>
>> Unless there are objections, I plan to apply these patches.
> Doesn't applying this patch contradict your earlier opinion?  This patch
> would still hide the affected controls from the guest because the host
> controls enlightened_vmcs_enabled.

It does.  Unfortunately the key sentence is "we're stuck with it for
existing Windows versions". :(

> Rather than update vmx->nested.msrs or filter vmx_get_msr(), what about
> manually adding eVMCS consistency checks on the disallowed bits and handle
> SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES as a one-off case by simply
> clearing it from the eVMCS?  Or alternatively, squashing all the disallowed
> bits.

Hmm, that is also a possibility.  It's a very hacky one, but I guess
adding APIC virtualization to eVMCS would require bumping the version to
2.  Vitaly, what do you think?

Paolo


  parent 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
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 [this message]
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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