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

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Message-ID: <dfdf6d93-a68c-bb07-e59e-8d888dd6ebb6@intel.com>
Date:   Fri, 16 Jun 2023 14:56:20 +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 6/16/2023 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?