Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <e9244de0-6fa8-e737-a38c-f0a6859ae592@intel.com>
Date:   Thu, 4 May 2023 14:59:35 +0800
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101
 Thunderbird/102.10.0
Subject: Re: [PATCH v2 10/21] KVM:x86: Add #CP support in guest exception
 classification
Content-Language: en-US
To:     Binbin Wu <binbin.wu@linux.intel.com>
CC:     <rick.p.edgecombe@intel.com>, <seanjc@google.com>,
        <pbonzini@redhat.com>, <peterz@infradead.org>,
        <john.allen@amd.com>, <kvm@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>
References: <20230421134615.62539-1-weijiang.yang@intel.com>
 <20230421134615.62539-11-weijiang.yang@intel.com>
 <d923f839-7505-21fc-2976-673c9e698b6f@linux.intel.com>
 <7bf51510-ca6e-d4b2-31bf-405258fd08e7@intel.com>
 <a11560cd-d6ad-ddb9-24ce-b45cd879227d@linux.intel.com>
From:   "Yang, Weijiang" <weijiang.yang@intel.com>
In-Reply-To: <a11560cd-d6ad-ddb9-24ce-b45cd879227d@linux.intel.com>
Content-Type: text/plain; charset="UTF-8"; format=flowed
Content-Transfer-Encoding: 8bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?L0FBbFluRitBOStYRzJ4d05KOWUvcXArSFpuYzRoSWM1Rlk0RzhmN09xTEN6?=
 =?utf-8?B?WHUyQkcyVC9XdUczZEExdUl3U25hRlFVdkxSUU5PVjVVcEFMWVN0aUFIZ2NY?=
 =?utf-8?B?ckNleU5mM091ZXhnVUNLQ1BnUzNVbE9EM3dBRUdPZlp2aTF1cThodkxTd2FE?=
 =?utf-8?B?bEpzUWdDVzhCTGJqck04Ym5YamhkdTNQd0ZPQUFNK1BXMlFyUTVzMGsxL0s0?=
 =?utf-8?B?UWY4dUlZMVp1MksvZ3dHMGQrK0NzUStld2E1VkRUQjR6OUEzUkZWR3lMYnBw?=
 =?utf-8?B?ZmlST2FMNHRVQWplbU0rUCt6R0hIRUJyUGlOcU9VNzY5elZqdldYQVc1QitO?=
 =?utf-8?B?Szg2MTE1Ly82SDhUOWMxNWJOUWd2WXpoZ2tWWTJyMkdmQmVSRmtrL2JuM2Ni?=
 =?utf-8?B?U09IeHZ5Mk42L1RJcGlmQzQvQmpHWlBicEEzaU1SOXdkalBuWmtuZHlabFJ1?=
 =?utf-8?B?ZklsenY1Q0ZGUXpoQmZZajlNMUxpSDFGWTJ4SjdLOGdnM04ya2xZam4weElB?=
 =?utf-8?B?aVZOWFZlbzdxR0Z5NGpza1hDSkpLSVorS29ZSWdlaHhialBGK0wzazJxWC9M?=
 =?utf-8?B?NkEycklENTR4Z3k2ei90Y051ZXJnWHdOOE1KWGJnNmc1N1hwQThoRUtKK1du?=
 =?utf-8?B?Zzl0QzRtbnFRZUNHOEcrK0p0cFN0L1Z0cHZOVUJUeFA1MGx3ZkxYN2R1dkhS?=
 =?utf-8?B?YnpHWGhnYndsK1l0cklqc3BMbU4rT2c5WFBkdnV0Ty83bWpHMFhHVmx5TUVW?=
 =?utf-8?B?NGZVSzFINzVWZlp4VFBoRlRXNkMyRXRTNHZsMXNLMWtKL0NDM2lsYVRzdHVM?=
 =?utf-8?B?RDVXNEYvYmhySStHMlBROUVObnFZNXNMMGpQVk9iY2NHSXBNVHFwdXVCd1E3?=
 =?utf-8?B?R3c5anpMdHl2L1BVRVhCWnUwUGNGUmRGcXFxd09uMEJGRmI0YjR5MUpNUnN6?=
 =?utf-8?B?eW5lR1I4UGRrNWRBcjdOTDdRZm1oZ1FvWHR6SXpHelJtSFBqSjZoeUMxWHlK?=
 =?utf-8?B?QVRtTzdIeGZ5SzFpd3NIUUtOc3k0RWUzMm1GQ1laSGlYdWIrVzVMMUdTa0E4?=
 =?utf-8?B?U0w4SlNzdWhjZDZtU1NwNUNSNnF4eG9HWUkva2JMbXNOem9BV3piWUNCTDlR?=
 =?utf-8?B?VlFUTjczYmkvbjBEeHdieldWenptdkx5aDVHNVRNQ25JTEg4OVl6bEdKQjhT?=
 =?utf-8?B?TjFIZHRNcWhqa1BtRDF3V1hPU0tkNmxVZXZ1VEpENjg3RUxSUGM4dkpaemZ2?=
 =?utf-8?B?OTVZOVZFZWdkeVgvZ2hzNExOYlN5dnNROXE5ZWN0RjRhWDVCcDBWcXJxR0NJ?=
 =?utf-8?B?MHQwYXoyb1JhN0MwajdlZnZEOVl3OHhLWlNjZHlKeVgzN2hHTTBNOU5YN0d6?=
 =?utf-8?B?WERObCtXSHZCZ3l4THVUL1VFZ1Q1ZTNzKzdEMWxqcGVybE9XcWMrUUdQQlg3?=
 =?utf-8?B?c2JrWE5FaEtzb1ZyTVVXRTRYN1dTUjBnNmM1S0J2OEs5M2ZFRXhZeDlrN0N1?=
 =?utf-8?B?bG1HU3hUQkF2WW9UcFd6aFFVeFpZbVk5VFkwSmo4R0pvK2MyVVJ6Q29PMXJ0?=
 =?utf-8?B?UEJZMUZ5U0NSNlBUczRRUkI2aytxSTVHcEhoUUgzV2NCMjhmeXlxREpaZWww?=
 =?utf-8?B?M2JqNVFPMFpNTndnWS94aE1wa3RmUjhUcnd5Qm5FTElYWWNJU3JVaUYxV0o3?=
 =?utf-8?B?MEtGMGRRU0JXa3VqajhCcENiOVlZV2FJQWRCN1VITEU5UjlXc2RMN3B1K3lB?=
 =?utf-8?B?Q0l5ZTJkQll0cm0vdTRXd002NVZhbEdSNjd0M3V5RUo5c0NOZkFtaUpQcEY2?=
 =?utf-8?B?OWo1K3NjUVcxVTU0dzJNOHRvQm9KZitKeW5JTXhNYWNnQ1lubkFOODNjcmZr?=
 =?utf-8?B?R0NKRTQwdVJvMEo0a0UrWXhOY2lMSDlYYTJ4dk5la0xZeEp2c28wc3RJQndw?=
 =?utf-8?B?QTFaeWJjRURjOTNacThSRDdaWDFZVjNTcE9DRlVxRkh6dXlBRFpBVjV2VklZ?=
 =?utf-8?B?bWhtL1ZNdjcwMTRkV0NOOWkyOElTUEI2QXNsMEhrSlRyU0Y0ZVNOZVp4aUZT?=
 =?utf-8?B?N1hSRmhKSVJqTUdDaElqbjF2Tm1wdHhaMElCTE1YU0hmRDVOYi9COE1IR05S?=
 =?utf-8?B?L3hTSTlqbUUzK3ZPekJOTE1GbzJHQVYwcTJOSUpvc2FIYXhBeGMrWGZjMGRI?=
 =?utf-8?B?YXc9PQ==?=
X-MS-Exchange-CrossTenant-Network-Message-Id: def39337-608e-4f46-584f-08db4c6d25cf
X-MS-Exchange-CrossTenant-AuthSource: PH0PR11MB4965.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 May 2023 06:59:47.5505
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: 6FYbo9Ij0BXsNkgtaqMvvXxP9hQ9vbq7G4sqYrk7sIHXHEMGueTp7SCEt2jZNyOoeMkjK4M2r2yAq6SOD211IA==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH3PR11MB7724
X-OriginatorOrg: intel.com
X-Spam-Status: No, score=-8.8 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
        DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,
        RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_NONE,T_SCC_BODY_TEXT_LINE,
        URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org


On 5/4/2023 1:36 PM, Binbin Wu wrote:
>
>
> On 5/4/2023 11:41 AM, Yang, Weijiang wrote:
>>
>> On 4/28/2023 2:09 PM, Binbin Wu wrote:
>>>
>>>
>>> On 4/21/2023 9:46 PM, 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.
>>>> See Intel's SDM for details.
>>>>
>> [...]
>>>>   -static int exception_class(int vector)
>>>> +static int exception_class(struct kvm_vcpu *vcpu, int vector)
>>>>   {
>>>>       switch (vector) {
>>>>       case PF_VECTOR:
>>>>           return EXCPT_PF;
>>>> +    case CP_VECTOR:
>>>> +        if (vcpu->arch.cr4_guest_rsvd_bits & X86_CR4_CET)
>>>> +            return EXCPT_BENIGN;
>>>> +        return EXCPT_CONTRIBUTORY;
>>> By definition, #CP is Contributory.
>>> Can you explain more about this change here which treats #CP as 
>>> EXCPT_BENIGN when CET is not enabled in guest?
>>
>> I check the history of this patch, found maintainer modified the 
>> patch due to some unit test issue in L1. You can check the
>>
>> details here:
>>
>> Re: [PATCH v15 04/14] KVM: x86: Add #CP support in guest exception 
>> dispatch - Sean Christopherson (kernel.org) 
>> <https://lore.kernel.org/all/YBsZwvwhshw+s7yQ@google.com/>
>>
> OK, is it better to add the reason in changelog?
>
> IIUC, a new contributory exception vector (if any) should be handled 
> similarly (i.e., treated as contributory conditionally) in the future, 
> right?

Agree although the issue happens in an uncommon case, I'll add some 
description in changelog in following version, thanks!

>
>
>>
>>>
>>> In current KVM code, there is suppose no #CP triggered in guest if 
>>> CET is not enalbed in guest, right?
>>
>> Yes.
>>
>>>>       case DE_VECTOR:
>>>>       case TS_VECTOR:
>>>>       case NP_VECTOR:
>>
>>
>> [...]
>>
>