linux-kernel - Re: [PATCH v2 2/3] KVM: VMX: Fix enable VPID even if INVVPID is not exposed in vmx capability

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Message-ID: <CANRm+CxJuYvMbrx72qCGKAdURZ+M=hm+oKXEF7K-g=u-mmTURw@mail.gmail.com>
Date:   Tue, 21 Mar 2017 16:58:45 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        kvm <kvm@...r.kernel.org>, Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>
Subject: Re: [PATCH v2 2/3] KVM: VMX: Fix enable VPID even if INVVPID is not
 exposed in vmx capability

2017-03-21 16:50 GMT+08:00 David Hildenbrand <david@...hat.com>:
> On 21.03.2017 05:18, Wanpeng Li wrote:
>> From: Wanpeng Li <wanpeng.li@...mail.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 below:
>>
>> KVM: entry failed, hardware error 0x7
>> EAX=00000000 EBX=00000000 ECX=00000000 EDX=000306c3
>> ESI=00000000 EDI=00000000 EBP=00000000 ESP=00000000
>> EIP=0000fff0 EFL=00000002 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=0
>> ES =0000 00000000 0000ffff 00009300
>> CS =f000 ffff0000 0000ffff 00009b00
>> SS =0000 00000000 0000ffff 00009300
>> DS =0000 00000000 0000ffff 00009300
>> FS =0000 00000000 0000ffff 00009300
>> GS =0000 00000000 0000ffff 00009300
>> LDT=0000 00000000 0000ffff 00008200
>> TR =0000 00000000 0000ffff 00008b00
>> GDT=     00000000 0000ffff
>> IDT=     00000000 0000ffff
>> CR0=60000010 CR2=00000000 CR3=00000000 CR4=00000000
>> DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000 DR3=0000000000000000
>> DR6=00000000ffff0ff0 DR7=0000000000000400
>> EFER=0000000000000000
>>
>> 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]=0).
>>   - If the logical processor supports VPIDs (IA32_VMX_PROCBASED_CTLS2[37]=1) but does
>>     not support the INVVPID instruction (IA32_VMX_EPT_VPID_CAP[32]=0).
>>
>> 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@...hat.com>
>> Cc: Radim Krčmář <rkrcmar@...hat.com>
>> Signed-off-by: Wanpeng Li <wanpeng.li@...mail.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(void)
>>       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 = 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 = 0;
>>       if (enable_shadow_vmcs)
>>
>
>
> --
>
> Thanks,
>
> David