Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:18 as permitted sender) client-ip=2620:137:e000::1:18;
Message-ID: <44b72da3-05d3-a9cb-eb74-43295383c9d0@amd.com>
Date:   Fri, 22 Apr 2022 12:27:11 -0500
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.5.0
Subject: Re: [PATCH v3 2/2] x86/sev: Get the AP jump table address from
 secrets page
Content-Language: en-US
To:     Michael Roth <michael.roth@amd.com>
Cc:     linux-kernel@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H . Peter Anvin" <hpa@zytor.com>,
        Kees Cook <keescook@chromium.org>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Tony Luck <tony.luck@intel.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        Venu Busireddy <venu.busireddy@oracle.com>,
        Joerg Roedel <jroedel@suse.de>,
        Tianyu Lan <Tianyu.Lan@microsoft.com>,
        Brijesh Singh <brijesh.singh@amd.com>
References: <20220422135624.114172-1-michael.roth@amd.com>
 <20220422135624.114172-3-michael.roth@amd.com>
 <c3baaf5d-db99-f432-125f-9884b57b40ef@amd.com>
 <20220422154056.lhzmii34he6blvwv@amd.com>
From:   Tom Lendacky <thomas.lendacky@amd.com>
In-Reply-To: <20220422154056.lhzmii34he6blvwv@amd.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?aWphZ01kYllzbGVCekZ4TGhUMG4zQXVjekd5dkJ4YnR0Q05EbVl0YkNNWEs1?=
 =?utf-8?B?WTMxNUlwQVR4eEszSnlabmRSSlhTWHkrS29GUTh3U25URGpuYUpYUmRPV0Q3?=
 =?utf-8?B?VFhYQ0dZeUo3ckdsdFVYYmRBQ2orMG5Qam1YejAzd0YzbUgwUEdzMjdFQWpv?=
 =?utf-8?B?Tm40aVlOYTFpWHh4bGhBU0FVaDErL2hXL0pvbkI3aGI4SmRlejRBU0xweWo1?=
 =?utf-8?B?aDdRQkhSRkIyN1dZSTVWTjA2bm0wcnBkU1IzQmtVdWlzMnVZdUpXRVpSY3k4?=
 =?utf-8?B?Z2dnWm1sQmNPeGg5LytRMWVyV1VSVE43UGlRZ3dHYmtuNStMVkhjWjg5N2x1?=
 =?utf-8?B?S3B6N3B2NW5yckJmNVJzQUQrcFNWUUhvQmJoKzIzSzlvMlh0WVhWT0pNOGxT?=
 =?utf-8?B?SDBuaFJVZ21LTXhSODY3RmxOWVU5SUtTR3kyQzdDdnpxNSs0U0d1TktlYWtv?=
 =?utf-8?B?SVBjNlQyUmZXTjY5YmkxMy9NMnZ5ZGhFUXdZRnhaTUIzZFo1a3VXSnJQYjBx?=
 =?utf-8?B?QytLK3RxN1JubXBCb2hQZlRjT2NjeEJWMHAweDZ2Tm5KTEtndmtDQWhYMXJT?=
 =?utf-8?B?VkE1VzJFeXk3cmFRNWwrUjZKa01zeHYvNVJybDVyNHFmYllGZWVMZFVCZXdY?=
 =?utf-8?B?U25OQ1crMmxwNHJWVk9SRFZMMFprMWcrdjMybjhHYjhJMXBOK1R2L1diZG1G?=
 =?utf-8?B?MWl1bTd0VGFiRE8xcWhRSmoxMlRnbEExYWJTQzlKeVRpWkFnVlRBa09rVENG?=
 =?utf-8?B?b2tlNWtHMU9CRkdmSjBrMUZCL2xTTjRKVGtwOGROZ05nODVjOG1pUjNxeHNz?=
 =?utf-8?B?OTlxRHBkSWZjbnlLY2p3Ym1hSk42dXZPRmVRWkNOckU5S1BydGZnZk11bE5M?=
 =?utf-8?B?NlQ4NGdpZHdKcytJOXJkbE5xMm9VQUx1Zkdpc3VmeWZ6MmVHbXdQQjljMDJS?=
 =?utf-8?B?VkNuZGxQRjhUQTZpS3BrMndUeDV3ekY2SURML3NZbzFTYXJRUElqV0ZUNGQ5?=
 =?utf-8?B?RkM2a0VNRlU5K3ByU25NRWxVdTZLQmoxcElDVjE2ZVBGWFozUlVTZ3RaUHJG?=
 =?utf-8?B?cGFzaFdlaS9zcW1oYklqNEtLZ0l4V3ZzaGNQa2lCcEVyRWFHNDhXQVNFdE44?=
 =?utf-8?B?K3lkd2tmK0Q2QzlCVWxzbzQxdkVpSWFLNnRFdDRMcm8wQUliTXZKYThhQW9L?=
 =?utf-8?B?bk41WlRxQU9xZ21xTnpUaUhCMjhyTVgybHhwaXdoNGFTaHQyOFp0QUJid0R3?=
 =?utf-8?B?TlNaWWZpVDJuRDRnMG85Z2xpM2xYYzE1VG1sYVk5K1lyVVJzWCtCaGxSdFVP?=
 =?utf-8?B?cndVRWo5VVZyMm5rYjdEbGJHU1dOeUtLT2h3Wjc4enl5aGZOa0ZJM3BCSWc2?=
 =?utf-8?B?bS91Z28zWEpuNDFoS1JYcTdEWVdSOWZaaVpwV2l4S0pBWjdldzF2T1pqVDJh?=
 =?utf-8?B?c2JWcjdQekZPRU1EQ3VhTUpWOEpMcDB3UkhGRVREQkxWZDRER1J4K3JsdHJy?=
 =?utf-8?B?Y1ZWMnJHejUvM0E4Njd1dk41TWZyUmpBYTRPUlVUTzBCN1cwRXFNTlVVeTFh?=
 =?utf-8?B?a0Rta2hISmlaRGtMeW51eXcwYWtKRmI0SDlJaWdVbXg5dWVJYTFtY3NwVWZ1?=
 =?utf-8?B?c1RmWHQ1SmVJOE1NZ2pKTVB0OWVOTnhkbEdIRE5PcnEwT0NBU2Z3OHhKUUNO?=
 =?utf-8?B?V0ZLaUg0TEFRRitHeXU0L1pZZHVYTVdRU0svSEdxQURUdlZhQzY2WFo2TXV6?=
 =?utf-8?B?SENMaTV2VGd6aU1CRkxoeUNoN1BiY1lUQmJoUHhvUTQ4M2pITWUrbloxaDNL?=
 =?utf-8?B?MEl5YlJvYUNHVTNzcEFMeDRDbDFZdmthRkdCMTREdS9hY20xckdwOTEwR1ZX?=
 =?utf-8?B?czdXK3FKSncrTkxUZlBWS2E4aXI0a0xadnY1R29kQlBxakx1dnJMOXJUd3Uv?=
 =?utf-8?B?bHRQZWRGQWNjVUFkdlZHSjBkVFllUkdNVG1TQ2c5Y1o2M01oS3kyVnN5NURZ?=
 =?utf-8?B?UElSem51bXZOaklIZFo4czVkT0pFd3NjcllDdzlvSXhicDhweVJ3ZlBZNVNL?=
 =?utf-8?B?VDh4RUlPVkZFWHNFRWNvL3NxWUZlRnpXd3VPMloxTHdmSllVRmk4bk9pdk1Q?=
 =?utf-8?B?aFd5NWhWUDBEVlRubmlFekZxZnNlQ2NXcTdvMVZBdjZwdFNhakJ0Ukc0UFkv?=
 =?utf-8?B?SEpVdmZldUYyWU10b2RtQks3MkJwM3BaMDhoY1R4UU8zN0RkZG5IbmRkUktx?=
 =?utf-8?B?eGdkaEtsem00cVA1dHZDdjQwbm9Xd2pWZldIRG5sUXlGbkpzWURyTW1TMG1J?=
 =?utf-8?B?czZWZVdYbkp1dzYyVnBCNHErMHpmWENBajdUMmU3UEp3M1htTEt6UT09?=
X-OriginatorOrg: amd.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 2fe3e955-4776-4cae-88d8-08da24855726
X-MS-Exchange-CrossTenant-AuthSource: DM4PR12MB5229.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Apr 2022 17:27:13.9769
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: GpsrLPDVkEcxN7TXlw9RVQ6mq5wEE0oDnGD2Cfg7AaQAVyhOZth7bRdIxrGNoGWmvbc73Y481pR3TNP9l/7lOg==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR12MB4160
X-Spam-Status: No, score=-3.1 required=5.0 tests=BAYES_00,DKIM_SIGNED,
	DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,NICE_REPLY_A,RDNS_NONE,SPF_HELO_NONE
	autolearn=unavailable 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 4/22/22 10:40, Michael Roth wrote:
> On Fri, Apr 22, 2022 at 10:15:08AM -0500, Tom Lendacky wrote:
>> On 4/22/22 08:56, Michael Roth wrote:
>>> From: Brijesh Singh <brijesh.singh@amd.com>
>>>
>>> The GHCB specification section 2.7 states that when SEV-SNP is enabled,
>>> a hypervisor must provide the AP jump table physical address through
>>
>> I missed this on the first version. It's not the hypervisor, but the guest
>> BIOS that directly provides the AP jump table physical address, in our case
>> OVMF sets the address in the SNP secrets page. This allows communication
>> between UEFI/BIOS and OS without hypervisor involvement.
> 
> How about this wording for the commit message?
> 
>    The GHCB specification section 2.7 states that when SEV-SNP is enabled,
>    a guest should not rely on the hypervisor to provide the address of the
>    AP jump table. Instead, if a guest BIOS wants provide an AP jump table,
>    it should record the address in the SNP secrets page so the guest
>    operating system can obtain it directly from there.
> 
>    Fix this on the guest kernel side by having SNP guests use the AP jump
>    table address published in the secrets page rather than issuing a GHCB
>    request to get it.

That sounds good to me.

Thanks,
Tom

> 
>>
>>> the SNP secrets pages.
>>>
>>> Fixes: 0afb6b660a6b ("x86/sev: Use SEV-SNP AP creation to start secondary CPUs")
>>> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
>>> [ mroth: improve error handling when ioremap()/memremap() return NULL ]
>>> [ mroth: don't mix function calls with declarations ]
>>> [ mroth: add missing __init ]
>>> Signed-off-by: Michael Roth <michael.roth@amd.com>
>>
>> With the commit message change:
>>
>> Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>