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From: Wanpeng Li <kernellwp@gmail.com>
Newsgroups: linux.kernel
Subject: Re: [PATCH v2 2/3] KVM: VMX: Fix enable VPID even if INVVPID is not  exposed in vmx capability
Date: Tue, 21 Mar 2017 10:00:02 +0100
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2017-03-21 16:50 GMT+08:00 David Hildenbrand <david@redhat.com>:
> On 21.03.2017 05:18, Wanpeng Li wrote:
>> From: Wanpeng Li <wanpeng.li@hotmail.com>
>>
>> This can be reproduced by running L2 on L1, and disable VPID on L0 if w/=
o
>> commit "KVM: nVMX: Fix nested VPID vmx exec control", the L2 crash as be=
low:
>>
>> KVM: entry failed, hardware error 0x7
>> EAX=3D00000000 EBX=3D00000000 ECX=3D00000000 EDX=3D000306c3
>> ESI=3D00000000 EDI=3D00000000 EBP=3D00000000 ESP=3D00000000
>> EIP=3D0000fff0 EFL=3D00000002 [-------] CPL=3D0 II=3D0 A20=3D1 SMM=3D0 H=
LT=3D0
>> ES =3D0000 00000000 0000ffff 00009300
>> CS =3Df000 ffff0000 0000ffff 00009b00
>> SS =3D0000 00000000 0000ffff 00009300
>> DS =3D0000 00000000 0000ffff 00009300
>> FS =3D0000 00000000 0000ffff 00009300
>> GS =3D0000 00000000 0000ffff 00009300
>> LDT=3D0000 00000000 0000ffff 00008200
>> TR =3D0000 00000000 0000ffff 00008b00
>> GDT=3D     00000000 0000ffff
>> IDT=3D     00000000 0000ffff
>> CR0=3D60000010 CR2=3D00000000 CR3=3D00000000 CR4=3D00000000
>> DR0=3D0000000000000000 DR1=3D0000000000000000 DR2=3D0000000000000000 DR3=
=3D0000000000000000
>> DR6=3D00000000ffff0ff0 DR7=3D0000000000000400
>> EFER=3D0000000000000000
>>
>> Reference SDM 30.3 INVVPID:
>>
>> Protected Mode Exceptions
>> #UD
>>   - If not in VMX operation.
>>   - If the logical processor does not support VPIDs (IA32_VMX_PROCBASED_=
CTLS2[37]=3D0).
>>   - If the logical processor supports VPIDs (IA32_VMX_PROCBASED_CTLS2[37=
]=3D1) but does
>>     not support the INVVPID instruction (IA32_VMX_EPT_VPID_CAP[32]=3D0).
>>
>> So we should check both VPID enable bit in vmx exec control and INVVPID =
support bit
>> in vmx capability MSRs to enable VPID. This patch adds the guarantee to =
not enable VPID
>> if INVVPID is not exposed in vmx capability MSRs.
>>
>
> Makes sense to me. Wonder how many systems are out there that have VPID
> but not INVVPID? Or will this never happen on real hardware?

At least this will not happen on the real hardware on my hands.

>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: Radim Kr=C4=8Dm=C3=A1=C5=99 <rkrcmar@redhat.com>
>> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
>> ---
>>  arch/x86/kvm/vmx.c | 9 ++++++++-
>>  1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index 06d8080..b310214 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -1239,6 +1239,11 @@ static inline bool cpu_has_vmx_invvpid_global(voi=
d)
>>       return vmx_capability.vpid & VMX_VPID_EXTENT_GLOBAL_CONTEXT_BIT;
>>  }
>>
>> +static inline bool cpu_has_vmx_invvpid(void)
>> +{
>> +     return vmx_capability.vpid & VMX_VPID_INVVPID_BIT;
>> +}
>> +
>>  static inline bool cpu_has_vmx_ept(void)
>>  {
>>       return vmcs_config.cpu_based_2nd_exec_ctrl &
>> @@ -6519,8 +6524,10 @@ static __init int hardware_setup(void)
>>       if (boot_cpu_has(X86_FEATURE_NX))
>>               kvm_enable_efer_bits(EFER_NX);
>>
>> -     if (!cpu_has_vmx_vpid())
>> +     if (!cpu_has_vmx_vpid() ||
>> +             !(cpu_has_vmx_invvpid()))
>
> This indentation looks weird. Can't this be fit into one line?

The same as cpu_has_vmx_ept_4levels().

>
>>               enable_vpid =3D 0;
>> +
>
> unrelated change

To make the vpid codes more clear. Please refer to other callees in
hardware_setup().

>
>>       if (!cpu_has_vmx_shadow_vmcs())
>>               enable_shadow_vmcs =3D 0;
>>       if (enable_shadow_vmcs)
>>
>
>
> --
>
> Thanks,
>
> David