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Date:   Fri, 3 Nov 2017 14:40:55 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Krish Sadhukhan <krish.sadhukhan@...cle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krcmar <rkrcmar@...hat.com>, kvm <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jim Mattson <jmattson@...gle.com>
Subject: Re: [PATCH v5 2/3] KVM: nVMX: Validate the IA32_BNDCFGS on nested VM-entry

2017-11-03 14:31 GMT+08:00 Krish Sadhukhan <krish.sadhukhan@...cle.com>:
>
>
> On 11/02/2017 05:50 PM, Wanpeng Li wrote:
>>
>> From: Wanpeng Li <wanpeng.li@...mail.com>
>>
>> According to the SDM, if the "load IA32_BNDCFGS" VM-entry controls is 1,
>> the
>> following checks are performed on the field for the IA32_BNDCFGS MSR:
>>   - Bits reserved in the IA32_BNDCFGS MSR must be 0.
>>   - The linear address in bits 63:12 must be canonical.
>>
>> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
>> Cc: Paolo Bonzini <pbonzini@...hat.com>
>> Cc: Radim Krčmář <rkrcmar@...hat.com>
>> Cc: Jim Mattson <jmattson@...gle.com>
>> Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>
>> ---
>> v3 -> v4:
>>   * simply condition
>>   * use && instead of nested "if"s
>>
>>   arch/x86/kvm/vmx.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index e6c8ffa..6cf3972 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -10805,6 +10805,11 @@ static int check_vmentry_postreqs(struct kvm_vcpu
>> *vcpu, struct vmcs12 *vmcs12,
>>                         return 1;
>>         }
>>   +     if (kvm_mpx_supported() &&
>> +               (is_noncanonical_address(vmcs12->guest_bndcfgs &
>> PAGE_MASK, vcpu) ||
>> +               (vmcs12->guest_bndcfgs & MSR_IA32_BNDCFGS_RSVD)))
>> +                       return 1;
>> +
>>         return 0;
>>   }
>>
>
> Hi Wanpeng,
>   The SDM check is performed only when "load IA32_BNDCFGS" VM-entry control
> is 1. But vmx_mpx_supported() returns true when both "load IA32_BNDCFGS" and
> "store IA32_BNDCFGS" VM-entry controls are 1. Therefore your check is
> performed when both controls are 1. Did I miss something here ?

https://lkml.org/lkml/2017/11/2/748 Paolo hopes the simplification.

Regards,
Wanpeng Li

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