Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.32 as permitted sender) client-ip=23.128.96.32;
Message-ID: <f7aa58e0-7fcd-35a9-d04c-1369a8cb0701@amd.com>
Date:   Mon, 16 Oct 2023 13:32:04 -0500
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101
 Thunderbird/91.2.1
Subject: Re: [PATCH] x86/mm: fix pg_level_to_pfn for 5-level paging mode.
Content-Language: en-US
To:     Ingo Molnar <mingo@kernel.org>
Cc:     dave.hansen@linux.intel.com, luto@kernel.org, tglx@linutronix.de,
        mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com,
        thomas.lendacky@amd.com, linux-kernel@vger.kernel.org,
        peterz@infradead.org
References: <20231013191703.422085-1-Ashish.Kalra@amd.com>
 <ZSpVtZhks7Wm5Upc@gmail.com>
From:   "Kalra, Ashish" <ashish.kalra@amd.com>
In-Reply-To: <ZSpVtZhks7Wm5Upc@gmail.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?VnZsZ21nZ3VDVlJrRFEyUDVuVm83OVFBSHVpNE1tblVXQjdWZzQ2aElFaGEz?=
 =?utf-8?B?ZTlSWWcwZmp6Y0ZVVzVsaUd4cmFxd3Q4YkFwRW5ucFFxQmR5SDRNblhja09k?=
 =?utf-8?B?ZFVWQjV3UkNlL1k2VUc4cEl0VFhFZlNnUEJwb1owRGIxcUdURmR1V1VtNzRa?=
 =?utf-8?B?eGwzMlVQYkl4ZGVTaVFtVHBkcXFwd0xTOTRFQnhVTjMxWDRPWCsySEh3YTlE?=
 =?utf-8?B?c0hka1g5UnN2SmsxbFVZb3lEQzQ1NUptNXZmVVBMb3NORDFPcTdzZ0NibXgv?=
 =?utf-8?B?MmRtU3VLZ0kxbytJWTRlQTVCUmdSSnc4WUwxcjJSQXNZTmU5cjQwVzlVMTlu?=
 =?utf-8?B?L2xiVG90bStoang0bEJuVkdOTFd2UkpoL0VCdW8zeEJOUENDMzBDTzhmVGxk?=
 =?utf-8?B?Mk1rUUVqZjVlMUdxT3RKTGRzbyt2QVJaL0s3cDNqY0xOcVdZbFUzdTNvMEpP?=
 =?utf-8?B?a3U5d0xQcmpUUzRIakgycXdiQzRnUTFsTk52NWJUWmhJQUY4QnZRTjVqeFZL?=
 =?utf-8?B?QStadk9mWFdpWitKaVhxYXh0TXRVZm5VTzZsUWJwOThPYVBBQTcrR0xtY1h1?=
 =?utf-8?B?akM2cnVjazh6VnVYVGpnMzhLd3R0dksraURsSnBpbERtYjJiTThOOUM2SVVK?=
 =?utf-8?B?UlVVdW5URGFiYUFaMmlsSC9MMUxscHRpYWVOQnBiMmJvVUR4YmJVeHMvLytp?=
 =?utf-8?B?NThDeW9lcUVmUCtqdldpc0puZlQ5M01ETk5rd2VDTkhoSkNmMmRqMGNLRXEy?=
 =?utf-8?B?WU40U2x3WEFVaWUzMGtseDZOREJIc053NWpCUjU2dFoycmp5bDZuczgwTlpi?=
 =?utf-8?B?VXpsRG5sMXI1SHh1UkZvaWJicFRIZHQ5L0VxamFBMGxDb2VBMHNndUhUdWRW?=
 =?utf-8?B?TWhoVXRDN3ZoVVZRdlNRV0tEd2dLekpOZWJWNVFXSGFsZWwzaUpCb2ppTWtw?=
 =?utf-8?B?bW1VN1lhbTVZRWowRzJ6a0F3WG9hSTlPdys0NzBWRjd3Y1RGUHZSYitGK3VX?=
 =?utf-8?B?MmtoUkhkVU0yb1NQNzdKRjdJdnkxOEx5YVM2SS9nUWNNUXlCSXhRWXEwNzU2?=
 =?utf-8?B?WG1JY3pDVjIzUTcwM0NyNng0Qm9FVTArRmtvZFROOW9NYjY1SWR4OHkxQnZJ?=
 =?utf-8?B?STVwS0hWalN1U2UxaTlsM0R0U1NlanJOYXJ0MHZ4Mzg1YlVpTis5eUF1TXBI?=
 =?utf-8?B?N3VaelpIemVFVk14SkpPT0o1SS92dTc0STlTZTAwclhLU0E1eUQ1NkJZb1hW?=
 =?utf-8?B?ZUVZR1RhVTc2emNDa0FjekY5cnQ1UVIxb0VtaEZwRW82dWNpQUV6aW1GS2FW?=
 =?utf-8?B?ZnJtdzB5RmdoYmdSTDkxZExUSHlkQWpYeWNkL3N6THRqYko4OXpVYzVaNDQw?=
 =?utf-8?B?OThKMW00ZnEvaG5UYi9XeGtka0txNTdHL1NHRTRRMzdpazgyc2U5UVhTZEgr?=
 =?utf-8?B?cy9Gbm02N0RFQ0FQUm1KS3lqVEx2emUyZHdaUVlSMEZWWTJJMVg5bWhEZ2FH?=
 =?utf-8?B?RzdaVXFQVFJQQTBuUFVXMlZYZDUyQkpwT01vdlhXZDJyUEtOVXk5YXQwaUoy?=
 =?utf-8?B?eDBIa21SMGJTTVhHV3RndXhNWXNnbGRneFFBWVRMSW03SmVSVnZCV1VxOEpj?=
 =?utf-8?B?UlRUZi92NWxoNVgxVitqTFFyMVYrQmg5WGxDZnFDbSt5RVJRUHhNOThhZDhM?=
 =?utf-8?B?a25tSHM4ZGp1NWJoU1pydnI1MFB0TWUzRXBHWmsxcU10K0luMTg3WjdidXVi?=
 =?utf-8?B?OFlFVXo0My9MaDVWaHgzanpMOWtvK0taWm5NQU9DWUVOd25DRnM2d0dZZUwx?=
 =?utf-8?B?K3J1cDU1SzZ6RVNqMGFYWk9LOVh4U0VhLzJnNVpqMjlPaUFvUlA2TmlSMm0v?=
 =?utf-8?B?SlBvZU9HcDhmM2M3YUdKY0ZLb1kycGt4c05mRWxlNFFmYW9ZSzEvTEVGY2Ez?=
 =?utf-8?B?ekZhVkFZRUlHanlMekdGWnpYNGRJMGI0WjN2enp2aEJUUjNEdzBWbFcvNHlP?=
 =?utf-8?B?a2p1Mkg2ZDBjVzRhUnFRMC8yZXdBN3NFQXJhSG9rT0tYdHV4K2RUb0I4M1p6?=
 =?utf-8?B?K05PRmFtcUdUYkJiYWtDQWJXNk1mWVR1c2xHcXp3VnNNQ2orV0k2UEVHUGVP?=
 =?utf-8?Q?rrEiCRxrk7D00wWOPRGhrljNF?=
X-OriginatorOrg: amd.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 223a17b4-9278-46d1-5f2f-08dbce7632a8
X-MS-Exchange-CrossTenant-AuthSource: SN6PR12MB2767.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Oct 2023 18:32:05.5736
 (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: uZlL1i2Ujv9fTq9PawQX5lvF8xmxc1pb1k5IvWIn9U5lOpQRcQ2bWT8pLv3PzmeBI+HRaS9CLcRKKMjmb7bakg==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB8451
X-Spam-Status: No, score=-4.2 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,
	DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS
	autolearn=unavailable autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on agentk.vger.email
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (agentk.vger.email [0.0.0.0]); Mon, 16 Oct 2023 11:32:24 -0700 (PDT)


On 10/14/2023 3:47 AM, Ingo Molnar wrote:
> 
> * Ashish Kalra <Ashish.Kalra@amd.com> wrote:
> 
>> From: Ashish Kalra <ashish.kalra@amd.com>
>>
>> Add support for 5-level paging in pg_level_to_pfn().
>>
>> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
>> ---
>>   arch/x86/mm/mem_encrypt_amd.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/arch/x86/mm/mem_encrypt_amd.c b/arch/x86/mm/mem_encrypt_amd.c
>> index 6faea41e99b6..45914568596a 100644
>> --- a/arch/x86/mm/mem_encrypt_amd.c
>> +++ b/arch/x86/mm/mem_encrypt_amd.c
>> @@ -267,6 +267,10 @@ static unsigned long pg_level_to_pfn(int level, pte_t *kpte, pgprot_t *ret_prot)
>>   		pfn = pud_pfn(*(pud_t *)kpte);
>>   		prot = pud_pgprot(*(pud_t *)kpte);
>>   		break;
>> +	case PG_LEVEL_512G:
>> +		pfn = p4d_pfn(*(p4d_t *)kpte);
>> +		prot = p4d_pgprot(*(p4d_t *)kpte);
>> +		break;
> 
> Mind explaining what happens if we don't have this fix, how you found it,
> which users are expected to be affected by it, whether that's the full
> known extent of 5-level paging support deficiencies in mem_encrypt_amd.c,foud 
> etc?
>

It was found during working on SNP guest kexec support, this helper 
function is used during early boot stage for setting of C-bit on the 
PTEs and additionally need this same helper for switching shared pages 
to private during guest kexec, so i believe this patch is needed.

Thanks,
Ashish

> In addition to such patches being much easier on the eyes, it also helps
> maintainers prioritize patches.
> 
> Thanks,
> 
> 	Ingo
>