Received-SPF: pass (google.com: domain of linux-kernel+bounces-128729-linux.lists.archive=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) client-ip=139.178.88.99;
Message-ID: <f1802e68-88b2-43f9-8344-d2a513e206a1@amd.com>
Date: Tue, 2 Apr 2024 16:31:30 -0500
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH] x86/sev: Apply RMP table fixups for kexec.
Content-Language: en-US
To: Borislav Petkov <bp@alien8.de>
Cc: bp@kernel.org, thomas.lendacky@amd.com, linux-kernel@vger.kernel.org,
 linux-tip-commits@vger.kernel.org, michael.roth@amd.com, x86@kernel.org
References: <2ab14f6f-2690-056b-cf9e-38a12dafd728@amd.com>
 <20240402163412.19325-1-bp@kernel.org>
 <6f0d2ccf-243c-4073-a470-21e2f404595a@amd.com>
 <359264a1-e4ef-438c-8f24-32848e131272@amd.com>
 <20240402174540.GAZgxERNxsRJUCb1yp@fat_crate.local>
 <37321af9-aee4-4ba6-81ac-0df4cef38644@amd.com>
 <20240402185039.GBZgxTfwvEP45OxVjm@fat_crate.local>
 <8daf448f-eb52-4b1f-9f98-099a83665321@amd.com>
 <20240402202118.GCZgxovu-pgPKYvner@fat_crate.local>
 <6fdb98f8-b4e2-474d-b8e9-c3092e77e56e@amd.com>
 <20240402212009.GEZgx2iZC_Plx-ajKW@fat_crate.local>
From: "Kalra, Ashish" <ashish.kalra@amd.com>
In-Reply-To: <20240402212009.GEZgx2iZC_Plx-ajKW@fat_crate.local>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0:
	=?utf-8?B?emxpVkpEL0thZHJlVERYRXB2aGZGVXQxRmIwc1ByYUorS1kyNlp4aEs0WGxX?=
 =?utf-8?B?eHM1cE1EVDQwMExuSTZIOEdXalovM2VQM21wTXpMR1dUTEp4dDc0QlRiOVNK?=
 =?utf-8?B?YTNFOTBvWE5FaGt4MGxCSFJ2THBRUFRIMG80OUI3dHVPUSticnpxbitsS3Bj?=
 =?utf-8?B?dTVnMFd5aUg4MGVGUmcrRlRqbHM5NndYN29yOWV1RjZpdHIwN2RMR3FCODE2?=
 =?utf-8?B?N0JoYnN1M2k5NkcwTjRNUmxPTWV5OWZsNEVxT1dxUnV3a1kraDF0a3NiVUF2?=
 =?utf-8?B?WXFHcDZsWE5xdFR0ZEk2YjI2NHpQa2l4c3c3L2c4MThTYi9sRVA0cUVzVEE0?=
 =?utf-8?B?ZENvRkdoakN2OUZFeENBVVlBT3ZaYVBjZzVZbGREM1RKdW9FZElNZVB5S1Vk?=
 =?utf-8?B?QlVuRXBlaEFEUDlWZklaeVJ5LzBDUVV6clBNZHA5MllaSmFqcmJmeTcrSExE?=
 =?utf-8?B?Y2M4WVByWmN0aEFHZEgrT0h4Ym5odUZLTnJRVlFCc2dacXZmWlgzRko3YWdE?=
 =?utf-8?B?UkF0eVp3VEFGMEtCZFN0MWx5WE9RMW5LNTdtb2N4cjJXTWY5ek1RaHZiRWNx?=
 =?utf-8?B?MjBHUWtJVlFUYjZXL1RUWWZTU2FGUEFvSjdQNi9ucDJXWGZKYWdTYmo2bTJt?=
 =?utf-8?B?VWVGK21rdEtNS2g0MWluaGxKbHpGWHNSbUMwSzlJR0ZEaUxHSEtURzdEUklq?=
 =?utf-8?B?MHp0VjlaVjNZRTNPY3RqSXlNOS9Bc3E3UW5MQWhRUG9VTkVra25xN2FRWnhI?=
 =?utf-8?B?dG9KT3dDWitLOG1aa3NOcDRpcUVZQzNoeVNTekFicGJZL1lhTUthdG1ybVFB?=
 =?utf-8?B?SGtsS2g5M3JGU3BBNHNDWjg4bndDbzdFcXNqRHVKd3MzemV1N0VBL3NYRTJr?=
 =?utf-8?B?b0pnbU1hYk9sMnhRRDByODE0U3ZDdUFyT3RCUzBmVnQyazRLVkJBMEJuU0hE?=
 =?utf-8?B?eCt3eEplUGZ3SzI2Q1cwd09yV2NvaTQ0NVc0TklMQXU4OTFzem1hcGk2aXFL?=
 =?utf-8?B?MlNUWWZkSy9aeGI5ZjU3TzNyRnM1bHJhdk15aVYzQWQ0RmNsK25qRlRISUli?=
 =?utf-8?B?RkRDYW52OFBHdHdtWkM3c0FVNzE1cnFLV3pqeUMrazF6OEtqODZJV0ZrTkhH?=
 =?utf-8?B?aFhTS2lBV2s5UVJBTW5pTENKVlNqMFFvNTB0R0pHcVhYYk1pRXVROTVDZmhp?=
 =?utf-8?B?QmVlcEFPdG9WRm14ZDNmeVAvcTdiaXdFS3FESDdaaGhBa1BvTGk5dW84S01v?=
 =?utf-8?B?RzArTm9sR2FMbTVxVklsMFdlbkhUK0pVS1BsNG1hQ3Y4ZFIwY0Rab2RXeUsw?=
 =?utf-8?B?Z3o5bW45V1pPbjMyTnl2dlNsR2RhZ2l5VXV0UW0wcW5nRHRkVnJZdmkwUDBu?=
 =?utf-8?B?MWhkKy9KaERnYnUwbUJsVkR0VEdHNmxuUW9CZ0RLUm5MVnBvWFR1di96Z3I4?=
 =?utf-8?B?a1p4Vy9NcnJNUXF4MmRzb09Ma0E5dk9MZnBubVFlQVNtYmFGWkNVck91eDhk?=
 =?utf-8?B?ZTdDTUJqRUo1NUhxWXVVZnNQSGJSOVVLTUF2YkVKcW5mbU5iRzU5ZWk5aS8x?=
 =?utf-8?B?a0Y1d0t4SkdPSkJxcmZiOHh4d0YxRng5cWlyQWNOTy9BUnJ0bFRJNmhsd3By?=
 =?utf-8?B?THBMMnc5YjYvbXBlVDBSTVNBTzdwK1A5N01IV1A2ZUhla1NCVEYrWXpDRGVN?=
 =?utf-8?B?ZHB0emI1ZzJxMUkxYzMwU1BlaFh3WHR6eTVEV1VHR1Z0c3F6YUtsKzR5KzVn?=
 =?utf-8?B?UXdEcVBycXZGL29MTVY2bWJBaTc5MG54QXFtSGV4TG9RMm5DLzRjNlZidzR6?=
 =?utf-8?B?RmdvVUN5dVdDbGIyMS9RKzQ2YnBpcngzSFlxMHRFRDQ2SWhoQXd4elE2TDMx?=
 =?utf-8?B?WWJyTUd6ZjQ5NkJtVnJTd0JrblJCbytiUnFrZEcrbVUzUWxZd1hTTVBVYUpL?=
 =?utf-8?B?a0NNWVJCUXhmU2hrVEhZaDB6c2szMXZTNjNTSjN5TXRlL1N2V3dld0hDV3Er?=
 =?utf-8?B?Z1lKWjJmYTFsOXp4MExuTEdVcUQxS0ZidDNNQWNPbW5acWFweEtId3ZoMzcx?=
 =?utf-8?B?QjhkaUNaOVBkc0NBV21KZW1sZCtDUHUyTVJtV21FWkIrS0c0NzN6OHduQkhk?=
 =?utf-8?Q?nuckCo3/ZdSBmbajo4k6oEVIF?=
X-OriginatorOrg: amd.com
X-MS-Exchange-CrossTenant-Network-Message-Id: a3291ec9-758d-4ee5-ca4b-08dc535c4458
X-MS-Exchange-CrossTenant-AuthSource: SN6PR12MB2767.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 02 Apr 2024 21:31:32.9808
 (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: zQkEiIzWTNoZTUmUIkoQPQeBpM+b5Drb5omr2ejmzR2UVzIq69MWjWYBFYSPhyT6CNWwvpwW92JJ8iHffwd11Q==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR12MB4211


On 4/2/2024 4:20 PM, Borislav Petkov wrote:
> On Tue, Apr 02, 2024 at 04:00:03PM -0500, Kalra, Ashish wrote:
>> The main issue with doing that in snp_rmptable_init() is that there is no
>> e820 API interfaces available to update the e820_table_kexec and
>> e820_table_firmware and e820_table_firmware has already been exposed to
>> sysfs.
> And?
>
> You can't change it later? Tried?
The main issue is there is no API interface available to do that, i will 
need to add new API interfaces to update the e820_table_kexec and 
e820_table_firmware and then will that be acceptable for a use case 
which can be handled via a platform specific quirk ?
>> The e820 API only exports e820__range_update() which *only* fixes
>> e820_table.
>>
>> The important point to note here is that in most cases BIOS would have
>> reserved RMP table start and end aligned to 2M boundary and setup the e820
>> table which the BIOS passes to the kernel as such,
> So what was this "RMP table start and end physical range may not be
> aligned to 2MB" in your commit message?
> /me is completely confused now.
>
> Or does "most cases" mean that there can be cases where the RMP table
> placement in the BIOS is not 2M aligned and then the kexec kernel could
> try to allocate from within that chunk and there's RMP faults?

Yes exactly, that's what the above comment means.

  That's why the above commit message says "may".

>
> And you want to allocate those chunks up to the 2M boundary
> unconditionally, regardless of SNP enablement?

My point is that we always keep the RMP table memory reserved regardless 
of SNP enablement, so these are simply fixups/adjustments on top of that 
reservation.

Thanks, Ashish

> Now look at your original commit message and tell me how much of what
> came out on this thread, was in it?
>
> Not a lot, I'd say...
>