From: Jim Mattson <jmattson@google.com>
To: Krish Sadhukhan <krish.sadhukhan@oracle.com>
Cc: Wanpeng Li <kernellwp@gmail.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Radim Krcmar <rkrcmar@redhat.com>, kvm <kvm@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v5 2/3] KVM: nVMX: Validate the IA32_BNDCFGS on nested VM-entry
Date: Fri, 3 Nov 2017 10:54:11 -0700 [thread overview]
Message-ID: <CALMp9eQ4hxGQkayDDmEyu_aq+ODR8R5_th2LZ06LYa-XnxpqjA@mail.gmail.com> (raw)
In-Reply-To: <7c2c39a3-8b24-e89a-1c67-385a5c6a2976@oracle.com>
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
next prev parent reply other threads:[~2017-11-03 17:54 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-03 0:50 [PATCH v5 1/3] KVM: X86: Fix operand/address-size during instruction decoding Wanpeng Li
2017-11-03 0:50 ` [PATCH v5 2/3] KVM: nVMX: Validate the IA32_BNDCFGS on nested VM-entry Wanpeng Li
[not found] ` <0b1d82f7-2fc6-9fc0-15a4-3500413814bd@oracle.com>
2017-11-03 6:40 ` Wanpeng Li
2017-11-03 17:13 ` Krish Sadhukhan
2017-11-03 17:54 ` Jim Mattson [this message]
2017-11-03 0:50 ` [PATCH v5 3/3] KVM: nVMX: Fix mmu context after VMLAUNCH/VMRESUME failure Wanpeng Li
2017-11-03 16:01 ` Jim Mattson
2017-11-04 0:07 ` Krish Sadhukhan
2017-11-08 21:47 ` Jim Mattson
2017-11-09 0:37 ` Wanpeng Li
2017-11-09 10:40 ` Paolo Bonzini
2017-11-09 10:47 ` Wanpeng Li
2017-11-09 11:05 ` Paolo Bonzini
2017-11-09 11:10 ` Wanpeng Li
2017-11-09 16:19 ` Jim Mattson
2018-02-05 18:44 ` Jim Mattson
2018-05-07 22:56 ` Jim Mattson
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