linux-kernel - Re: [PATCH v2 2/2] KVM: VMX: Fix VPID capability detection

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Date:   Wed, 18 Oct 2017 08:51:51 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Jim Mattson <jmattson@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        kvm list <kvm@...r.kernel.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>
Subject: Re: [PATCH v2 2/2] KVM: VMX: Fix VPID capability detection

2017-10-18 1:48 GMT+08:00 Paolo Bonzini <pbonzini@...hat.com>:
> On 17/10/2017 19:43, Jim Mattson wrote:
>>> +               &vmx_capability.ept, &vmx_capability.vpid);
>>> +
>>>         if (_cpu_based_2nd_exec_control & SECONDARY_EXEC_ENABLE_EPT) {
>>>                 /* CR3 accesses and invlpg don't need to cause VM Exits when EPT
>>>                    enabled */
>>>                 _cpu_based_exec_control &= ~(CPU_BASED_CR3_LOAD_EXITING |
>>>                                              CPU_BASED_CR3_STORE_EXITING |
>>>                                              CPU_BASED_INVLPG_EXITING);
>>> -               rdmsr(MSR_IA32_VMX_EPT_VPID_CAP,
>>> -                     vmx_capability.ept, vmx_capability.vpid);
>>> -       }
>>> +       } else
>>> +               vmx_capability.ept = 0;
>> I would expect vmx_capability.ept to already be 0 here. Otherwise, L0
>> is reporting inconsistent VMX capabilities.
>>
>>> +       if (!(_cpu_based_2nd_exec_control & SECONDARY_EXEC_ENABLE_VPID))
>>> +               vmx_capability.vpid = 0;
>> I would expect vmx_capability.vpid to already be 0 here. Otherwise, L0
>> is reporting inconsistent VMX capabilities.
>>
>
> That's true, but I think it's better to be safe.  Maybe add a pr_warn if
> it is not zero?

Will do in v3.

Regards,
Wanpeng Li