linux-kernel - Re: [PATCH v3 10/21] KVM:x86: Add #CP support in guest exception classification

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Date:   Mon, 19 Jun 2023 17:28:26 +0800
From:   "Yang, Weijiang" <weijiang.yang@...el.com>
To:     Sean Christopherson <seanjc@...gle.com>
CC:     Chao Gao <chao.gao@...el.com>, <pbonzini@...hat.com>,
        <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <peterz@...radead.org>, <rppt@...nel.org>,
        <binbin.wu@...ux.intel.com>, <rick.p.edgecombe@...el.com>,
        <john.allen@....com>
Subject: Re: [PATCH v3 10/21] KVM:x86: Add #CP support in guest exception
 classification


On 6/17/2023 2:57 AM, Sean Christopherson wrote:
> On Fri, Jun 16, 2023, Weijiang Yang wrote:
>> On 6/16/2023 7:58 AM, Sean Christopherson wrote:
>>> On Thu, Jun 08, 2023, Weijiang Yang wrote:
>>>> On 6/6/2023 5:08 PM, Chao Gao wrote:
>>>>> On Thu, May 11, 2023 at 12:08:46AM -0400, Yang Weijiang wrote:
>>>>>> Add handling for Control Protection (#CP) exceptions(vector 21).
>>>>>> The new vector is introduced for Intel's Control-Flow Enforcement
>>>>>> Technology (CET) relevant violation cases.
>>>>>>
>>>>>> Although #CP belongs contributory exception class, but the actual
>>>>>> effect is conditional on CET being exposed to guest. If CET is not
>>>>>> available to guest, #CP falls back to non-contributory and doesn't
>>>>>> have an error code.
>>>>> This sounds weird. is this the hardware behavior? If yes, could you
>>>>> point us to where this behavior is documented?
>>>> It's not SDM documented behavior.
>>> The #CP behavior needs to be documented.  Please pester whoever you need to in
>>> order to make that happen.
>> Do you mean documentation for #CP as an generic exception or the behavior in
>> KVM as this patch shows?
> As I pointed out two *years* ago, this entry in the SDM
>
>    — The field's deliver-error-code bit (bit 11) is 1 if each of the following
>      holds: (1) the interruption type is hardware exception; (2) bit 0
>      (corresponding to CR0.PE) is set in the CR0 field in the guest-state area;
>      (3) IA32_VMX_BASIC[56] is read as 0 (see Appendix A.1); and (4) the vector
>      indicates one of the following exceptions: #DF (vector 8), #TS (10),
>      #NP (11), #SS (12), #GP (13), #PF (14), or #AC (17).
>
> needs to read something like
>
>    — The field's deliver-error-code bit (bit 11) is 1 if each of the following
>      holds: (1) the interruption type is hardware exception; (2) bit 0
>      (corresponding to CR0.PE) is set in the CR0 field in the guest-state area;
>      (3) IA32_VMX_BASIC[56] is read as 0 (see Appendix A.1); and (4) the vector
>      indicates one of the following exceptions: #DF (vector 8), #TS (10),
>      #NP (11), #SS (12), #GP (13), #PF (14), #AC (17), or #CP (21)[1]
>
>      [1] #CP has an error code if and only if IA32_VMX_CR4_FIXED1 enumerates
>          support for the 1-setting of CR4.CET.

OK, I'll route the messages to related person, thanks!