diff mbox

[v5,2/3] KVM: nVMX: Validate the IA32_BNDCFGS on nested VM-entry

Message ID 1509670249-4907-2-git-send-email-wanpeng.li@hotmail.com (mailing list archive)
State New, archived
Headers show

Commit Message

Wanpeng Li Nov. 3, 2017, 12:50 a.m. UTC 
From: Wanpeng Li <wanpeng.li@hotmail.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@oracle.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Jim Mattson <jmattson@google.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
---
v3 -> v4:
 * simply condition
 * use && instead of nested "if"s

 arch/x86/kvm/vmx.c | 5 +++++
 1 file changed, 5 insertions(+)

Comments

Wanpeng Li Nov. 3, 2017, 6:40 a.m. UTC | #1 
2017-11-03 14:31 GMT+08:00 Krish Sadhukhan <krish.sadhukhan@oracle.com>:
>
>
> On 11/02/2017 05:50 PM, Wanpeng Li wrote:
>>
>> From: Wanpeng Li <wanpeng.li@hotmail.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@oracle.com>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: Radim Krčmář <rkrcmar@redhat.com>
>> Cc: Jim Mattson <jmattson@google.com>
>> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.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
Krish Sadhukhan Nov. 3, 2017, 5:13 p.m. UTC | #2 
On 11/02/2017 11:40 PM, Wanpeng Li wrote:
> 2017-11-03 14:31 GMT+08:00 Krish Sadhukhan <krish.sadhukhan@oracle.com>:
>>
>> On 11/02/2017 05:50 PM, Wanpeng Li wrote:
>>> From: Wanpeng Li <wanpeng.li@hotmail.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@oracle.com>
>>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>>> Cc: Radim Krčmář <rkrcmar@redhat.com>
>>> Cc: Jim Mattson <jmattson@google.com>
>>> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.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
I got that simplification and your changes look good to me.


However, I am still curious know the reason why vmx_mpx_supported() 
returns true only when both controls are true whereas the SDM states the 
following:

    "IA32_BNDCFGS (64 bits). This field is supported only on processors 
that support either the 1-setting of the  “load IA32_BNDCFGS” VM-entry 
control or that of the “clear IA32_BNDCFGS” VM-exit control."

Thanks,
Krish
Jim Mattson Nov. 3, 2017, 5:54 p.m. UTC | #3 
KVM chooses not to support MPX in the guest unless both of these
control bits are supported by the platform.

On Fri, Nov 3, 2017 at 10:13 AM, Krish Sadhukhan
<krish.sadhukhan@oracle.com> wrote:
>
>
> On 11/02/2017 11:40 PM, Wanpeng Li wrote:
>>
>> 2017-11-03 14:31 GMT+08:00 Krish Sadhukhan <krish.sadhukhan@oracle.com>:
>>>
>>>
>>> On 11/02/2017 05:50 PM, Wanpeng Li wrote:
>>>>
>>>> From: Wanpeng Li <wanpeng.li@hotmail.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@oracle.com>
>>>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>>>> Cc: Radim Krčmář <rkrcmar@redhat.com>
>>>> Cc: Jim Mattson <jmattson@google.com>
>>>> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.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
>
> I got that simplification and your changes look good to me.
>
>
> However, I am still curious know the reason why vmx_mpx_supported() returns
> true only when both controls are true whereas the SDM states the following:
>
>    "IA32_BNDCFGS (64 bits). This field is supported only on processors that
> support either the 1-setting of the  “load IA32_BNDCFGS” VM-entry control or
> that of the “clear IA32_BNDCFGS” VM-exit control."
>
> Thanks,
> Krish
diff mbox

Patch

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;
 }