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From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>,
	Paolo Bonzini <pbonzini@redhat.com>
Cc: 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 10:37:16 +0100
Message-ID: <87zhefsugj.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <20200122054724.GD18513@linux.intel.com>

Sean Christopherson <sean.j.christopherson@intel.com> writes:

> On Sat, Jan 18, 2020 at 10:42:31PM +0100, Paolo Bonzini wrote:
>> IMHO the features should stay available in case the guest chooses not to
>> use eVMCS.  A guest that uses eVMCS should know which features it cannot
>> use and not enable them.
>
> Makes sense, wasn't thinking about the scenario where the guest doesn't
> support eVMCS or doesn't want to use it for whatever reason.
>
> 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?

Unfortunately, this doesn't work because ... Windows. Not only Hyper-V
enables SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES, it actually expects it
to work (somehow) so when I do

diff --git a/arch/x86/kvm/vmx/evmcs.c b/arch/x86/kvm/vmx/evmcs.c
index 72359709cdc1..e6c30eec2817 100644
--- a/arch/x86/kvm/vmx/evmcs.c
+++ b/arch/x86/kvm/vmx/evmcs.c
@@ -361,11 +361,5 @@ int nested_enable_evmcs(struct kvm_vcpu *vcpu,
        if (evmcs_already_enabled)
                return 0;
 
-       vmx->nested.msrs.pinbased_ctls_high &= ~EVMCS1_UNSUPPORTED_PINCTRL;
-       vmx->nested.msrs.entry_ctls_high &= ~EVMCS1_UNSUPPORTED_VMENTRY_CTRL;
-       vmx->nested.msrs.exit_ctls_high &= ~EVMCS1_UNSUPPORTED_VMEXIT_CTRL;
-       vmx->nested.msrs.secondary_ctls_high &= ~EVMCS1_UNSUPPORTED_2NDEXEC;
-       vmx->nested.msrs.vmfunc_controls &= ~EVMCS1_UNSUPPORTED_VMFUNC;
-
        return 0;
 }
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index bb8afe0c5e7f..cd1f5a1c884b 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -1590,7 +1590,7 @@ static int copy_enlightened_to_vmcs12(struct vcpu_vmx *vmx)
                        evmcs->pin_based_vm_exec_control;
                vmcs12->vm_exit_controls = evmcs->vm_exit_controls;
                vmcs12->secondary_vm_exec_control =
-                       evmcs->secondary_vm_exec_control;
+                       evmcs->secondary_vm_exec_control & ~SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES;
        }
 
        if (unlikely(!(evmcs->hv_clean_fields &

Hyper-V 2016 with > 1 vCPU fails to boot :-(

-- 
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
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 [this message]
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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