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: <a0948545-1d2b-fdd2-3f7a-1f6a255162f4@oracle.com>
Date:   Thu, 27 Apr 2023 15:38:35 -0700
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0)
 Gecko/20100101 Thunderbird/102.10.0
Subject: Re: [RFC v3 21/21] x86/boot/compressed/64: use 1GB pages for mappings
Content-Language: en-US
To:     "H. Peter Anvin" <hpa@zytor.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Cc:     tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org,
        dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org,
        rppt@kernel.org, akpm@linux-foundation.org, ebiederm@xmission.com,
        keescook@chromium.org, graf@amazon.com, jason.zeng@intel.com,
        lei.l.li@intel.com, steven.sistare@oracle.com,
        fam.zheng@bytedance.com, mgalaxy@akamai.com,
        kexec@lists.infradead.org
References: <1682554137-13938-1-git-send-email-anthony.yznaga@oracle.com>
 <1682554137-13938-22-git-send-email-anthony.yznaga@oracle.com>
 <70EB1774-A782-47FB-A8EA-534E66A551F6@zytor.com>
From:   Anthony Yznaga <anthony.yznaga@oracle.com>
In-Reply-To: <70EB1774-A782-47FB-A8EA-534E66A551F6@zytor.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?K2U2dWUyV3FpNWt3c1BOckJTMllZd09qUWhQMVZqd2NVOTJKVFZzZFBQMG15?=
 =?utf-8?B?ejdwLzVWZmlPZnc0VFA2RStzbUZvRnZJQXpieWdqbFRmS1l1elErYnpNa3pn?=
 =?utf-8?B?VlUxQ3NMbUlRM2t0bC9KbHFtYWpUVGN1Mlc4Nmt2RE5SZ05ZYmNoZEo3UVZp?=
 =?utf-8?B?TTVKcVJYRFl4L0hYb2pmSWgwczZ1aEVGb2doWWJKL2JMQlFmZi9kNFBQSWgv?=
 =?utf-8?B?NXZaa3ltWHVBVWx0ejU0M2dOMnM3TXBTVnJ5RzlQZGx6ditkdUVBZHNXUk04?=
 =?utf-8?B?NmNRKzBqZThQMzdBbm5aazhndkpxUVFqQXdXUzFJRmswbUZGRUQrSDFmYkhP?=
 =?utf-8?B?aVhwSTFHcDlhWSt6SUpuZ3B3RzQyOWpxUHB3WW1TcHhKbGNaQkFHcnIxQ0Fi?=
 =?utf-8?B?ZDgvSVFjYURWdEdISHNZRzlPaG9OclVoVlVMY0VTQk02T2podkFmYTcxdDJI?=
 =?utf-8?B?d0hnV012dldkREJ2WWFUQ2tGQzFmeHRuNG9uaSs5cnl5a2VrY3Y2akpTVTlL?=
 =?utf-8?B?S09wek5rUGRPV1gzbndtWDFMUkt1L1Z3V2YwT0YvenBZekNHaHRQRHArZUp1?=
 =?utf-8?B?NjlZNHZvdEhSWjRGN25OYW9NUHdQaXh2SzBIdlFXaXhxbTBoVTRiRDN3aHY4?=
 =?utf-8?B?cE0ya1dQQ2t5QUFXNTJBdkQvMDE2SDlBSmFjWVRhRTFZdVhyMzNBQTBYS2x6?=
 =?utf-8?B?Z2JCYms4dWtYWVZMWk1IZFNaeEJsa1lZL3RUOTdjb1JWNFgwSnRoU1FrYzV5?=
 =?utf-8?B?OFU5bjJKZ01HVDFvelJOR1BCM3R2ajI1bFBhOWV6ZE53RUNQejFpTnVjWlN2?=
 =?utf-8?B?aTBrY1FsWmQvU3lqRTZNbThkUjFMRzFDbmcwZjZvcWNRY1B0cDVhaHRmVkdx?=
 =?utf-8?B?NnNvWUxnbnM5Q0NrT3hLazhhcUJXRXJKL3FYUi8zVUVFOURXSFlvZHpwRFcx?=
 =?utf-8?B?N2NvZm1QVFBHWjNJSkM2TmJDTmhhY1pieFdkSGhKUmtyU3JCNzQvMFpHN3hz?=
 =?utf-8?B?NkJaWFB1aElERU5DTWIxQlYvSU8yOVBCc0JuSWp6UDJMZ09pRW5SMzJxMTZj?=
 =?utf-8?B?MDdQZ2pTeU0wcHdrcFJ0Y0xQejQyVnJnYkdWUk1Hd0x5RzVGWDZaRms0M2tM?=
 =?utf-8?B?ZWJFdEhrTG5NUFVuY1E5ZUlhb1RhM1dieWs1N2I5ZXJJNUM1REo3Y0RrZmVx?=
 =?utf-8?B?dmx6WitJcUFZdjhJL2hLdlJucSttd1RjNDhXeDRKWEN0aDZweDB1Q1BwaC9R?=
 =?utf-8?B?aG9CWEZmNktyTERlVHVHVmx0cnNSeCtaZC9IWm1ZQzVTUlJpYVNVRmZNTnp5?=
 =?utf-8?B?M0x2UmZhWnRHOEx5TGNMMVVEclI5Z2ZmWGE5VkpKRXU3aE1mWG1waFJMNkhp?=
 =?utf-8?B?NUEzRFBsSkFBanhKdnVsNkxTeGNXUk9PelBpelBEaTZ5T0pCL1AyT2lHejdD?=
 =?utf-8?B?RmdPVU0wTk9RQnAyZXRiWGhJdHZTVHZKK05PZEh1cGhNZnQvOEZSc3lpdEp6?=
 =?utf-8?B?WFhiUWhrRTFoWHpGR09sU2tzZmRkWFlON2VobTcvaThmWEVlMGZ4RlhwZVNi?=
 =?utf-8?B?WGZOU1J6dVBvMHdyNUVJY3NhU3ZZTzM4OEJFNUMxNDRNVVhrRlBJcE5BZW5s?=
 =?utf-8?B?d1BjdVBPdzRmcGFGdENJSy9pL0xycCtJQUY3WWZQWVB2K1IzelNreHdPUVRo?=
 =?utf-8?B?N3J5MzRUR2RuMDJ4cld0WHZWWnNCczg3ZHRwaEtxQm15WE56R1c2V3A3cVU1?=
 =?utf-8?B?Z0s5WTVyOTNWODQ1ZHB3MVR5cXArMEI0aDY5NTMxY3BQcmJKajQ1cFhRNDJU?=
 =?utf-8?B?ekRHMmJHSm1BTUg3bzRQNkVwQzNCZ28vbnc5UDVaSzBvZFVLVmh0aTNwTXFD?=
 =?utf-8?B?Q2JTWmMvQWpVdlFhZE9PUlFhTkRpMFFUMkNjSlNkdlJicE43clR0cjdhYnZP?=
 =?utf-8?B?SVpsNDYyMHJRNFpoV24zWEROelFBaXRlR1pBTXd5UkxobnRJd0FUeFVodW5y?=
 =?utf-8?B?WmV5TWtCQW1WMzRJaVJlZEs3WjdvNFRETUVlaUpyT1BuNEo5aUZzZ2R1ZHFH?=
 =?utf-8?B?V3REam1LcG1Pa09YV0pmS2xiOWxWQ2hDYXVGQVVSNTQxZzdYKyt2UWFVclZK?=
 =?utf-8?B?cUZyK1JuVEJZOS9aelZWNnMrRDFJMi9xa29UbklrTWI1L2hHcHVzT1ZqTGxI?=
 =?utf-8?B?RXc9PQ==?=
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: =?utf-8?B?U3lxejZZWTJ2aW1RakR5UklDQU1ieVpCYytSSVp6KzFqVkNja25YUmNQUzVX?=
 =?utf-8?B?S3lDVWh5c0p3aFhhODlCWHBvSkZYbGtLZjMvNnJBRHU2N2N2S3grbXI5TTJv?=
 =?utf-8?B?V3Q1c3VoVkVMSUFGdlZCOHdYRFpYMy9BVUdrQlBVTFk0TVJiTnQxVWxxYWJD?=
 =?utf-8?B?UWZIZnBaR213VE5HOXVsK21xWk5EcUtlNHc4NTdVYUU5c3lLZkh3UE5GUHkw?=
 =?utf-8?B?WURMTVNuNXNmMHdQQmhRejF0SE4zRUdENE13Z3JXVVBTYlpJNmw1SWpvREdm?=
 =?utf-8?B?blFUUlc1endOcmhPL3B5SXFCMWcxTXhtQ1IxdytpMnVCd0tuNW4xTjJHMVcr?=
 =?utf-8?B?bU02Y2pmaUhic24xTE0xNFkwMkE4TFZKZHhlUS9nc3ZoOVJlZFlRNHZ5TGha?=
 =?utf-8?B?MGxEUnJDbVd0VWZ0T2pFU29mbmFtWHdSaE1ZQ1NadHFXWktWYlVyaXo2Zlpz?=
 =?utf-8?B?c3o3T3E0bDh1Si9mTmxibXZCSUZRajZPMC95NVI1dEVoKzE1eEd4UGpQb1c4?=
 =?utf-8?B?V21hc2FncmFHaERCcmNuQm5jM0RXd0o4cHhZS2owblEvVC9FWTgxV2lGS1Ay?=
 =?utf-8?B?dERuZXg0emxHa2RWbDZLQnl3bVNGVWZmcEgyMU15VHpOWDhPTnpxUUlHZjVM?=
 =?utf-8?B?UmJDQmRJMHhuNXI2Um9wbTB4TzBxL09DRkRBYmtsZFUvV1prSDAraFdhd0Ev?=
 =?utf-8?B?bExlSUZvblhoTUh0aHl1bkZEa1F5SzNWeFRuQzJvRUN2eFNFdEhaQklqbS9r?=
 =?utf-8?B?SWRxYWRPSjZvTXZ5dW5MZDlEYnd5cDhLeFllcmNDcjNCUW03U1NIa1ZPeVZI?=
 =?utf-8?B?UTRBSUdWTGh0dEY5S3ZhemNtWlZsT1YyY3RzMlRBbHh2bFo3RkEyaHBpTlJB?=
 =?utf-8?B?OE9mcHZrUkExN016UEJKd1JVd0RNNGcxNENwbWx3VHU2ZHphODNUdU53MXFS?=
 =?utf-8?B?UW5ScEFyWmtSRE5ENzVCYVovWFkyUkptTkl6c1BWbmlyTi9EMTZRVlVTbUFs?=
 =?utf-8?B?MHBJa1ZwNUFkV3BPdWYwMk5VdjR4OW02dDdIdDdIUXkwMDVWTStvbkU4aE13?=
 =?utf-8?B?QjJ4elpsV0RLM0tkQy9aZVBUc0VuRkhpOERlc3BzOGtXWWlGMDA5clIzM1RB?=
 =?utf-8?B?STB5bVdFejN2c1BSZ2NGWHBJM29FQzNRTEU4N3l2RGtHTjFsY1paM2pTemVy?=
 =?utf-8?B?T1pTaEJjRTFodG1jS3FCbVQ0Q3Y5aStuMkhLUXJsTzFjeUs5NVFpWitqMXdw?=
 =?utf-8?B?aGtHSlBaeFBiQmNXYmg3d0RnL1JtbnUrUUtTUkZvbzFKdjBFdW5TZC82aFg1?=
 =?utf-8?B?dEoyNVY0UFRob0xaa204L3N3S2JoZVN2WXd6ZmIxVElrZUhEQlBOWXNPWTM4?=
 =?utf-8?B?TE9EMjZ3NWI3OXRxMGcxNEppUmtlN0p2dXRLaUdpc0dmTW94UXFvS3hFMzV6?=
 =?utf-8?B?SU0xYVdsdk5PQXlkRnRzOWNYaHRUZHA2Qm9qLzdvTGdLa1FWMHNsODBuTG5l?=
 =?utf-8?B?bmprMld0QlNOYnJlWlNoRUhzK0ZFNWJrcm9LOU9DRUx4WCs5aFRudUFsYm9G?=
 =?utf-8?B?OHEzVmsvTFA4ZHhES3lhaTJ6SUJCSHlITGd4ZXQ4TW8wVmdyTEtFUlprMFk5?=
 =?utf-8?B?dmgzT1FpczFOZVppVTVRWkhBOHllMEh6NmMrWXhOL0c4aldZdUNrOEVmTlVs?=
 =?utf-8?B?dXZQZTJ0Z0txWTI2T1ZqMXo1SFF0OU1LclVlK2dGUnJMRUdvbTFUNWFEdVg2?=
 =?utf-8?Q?w+Qo8bsKR9ejYtA0fjGZp1nbw1nxna5noz9lkzC?=
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 3ae8a433-796b-4d40-a0f2-08db47702729
X-MS-Exchange-CrossTenant-AuthSource: BYAPR10MB2438.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Apr 2023 22:38:42.3802
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: j7Zplnb5y1ETnzO9SboTTUvAAOdeM3PXjZFAximp815OIjk3D30Ar24Hoc9cgaSIdrf9PpNXZO6QQLLC9TMXc2AmsDKZ1AkIfQtAd49O9jM=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW4PR10MB6536
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.254,Aquarius:18.0.942,Hydra:6.0.573,FMLib:17.11.170.22
 definitions=2023-04-27_09,2023-04-27_01,2023-02-09_01
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 mlxlogscore=999
 adultscore=0 malwarescore=0 mlxscore=0 spamscore=0 bulkscore=0
 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1
 engine=8.12.0-2303200000 definitions=main-2304270200
X-Proofpoint-GUID: rpupowy-FKtqEkReBNRwiWNFqJDhLoNu
X-Proofpoint-ORIG-GUID: rpupowy-FKtqEkReBNRwiWNFqJDhLoNu
X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00,DKIM_SIGNED,
        DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,RCVD_IN_DNSWL_LOW,
        RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,T_SCC_BODY_TEXT_LINE
        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 4/27/23 11:40 AM, H. Peter Anvin wrote:
> On April 26, 2023 5:08:57 PM PDT, Anthony Yznaga <anthony.yznaga@oracle.com> wrote:
>> pkram kaslr code can incur multiple page faults when it walks its
>> preserved ranges list called via mem_avoid_overlap().  The multiple
>> faults can easily end up using up the small number of pages available
>> to be allocated for page table pages.
>>
>> This patch hacks things so that mappings are 1GB which results in the need
>> for far fewer page table pages.  As is this breaks AMD SEV-ES which expects
>> the mappings to be 2M.  This could possibly be fixed by updating split
>> code to split 1GB page if the aren't any other issues with using 1GB
>> mappings.
>>
>> Signed-off-by: Anthony Yznaga <anthony.yznaga@oracle.com>
>> ---
>> arch/x86/boot/compressed/ident_map_64.c | 9 +++++----
>> 1 file changed, 5 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/x86/boot/compressed/ident_map_64.c b/arch/x86/boot/compressed/ident_map_64.c
>> index 321a5011042d..1e02cf6dda3c 100644
>> --- a/arch/x86/boot/compressed/ident_map_64.c
>> +++ b/arch/x86/boot/compressed/ident_map_64.c
>> @@ -95,8 +95,8 @@ void kernel_add_identity_map(unsigned long start, unsigned long end)
>> 	int ret;
>>
>> 	/* Align boundary to 2M. */
>> -	start = round_down(start, PMD_SIZE);
>> -	end = round_up(end, PMD_SIZE);
>> +	start = round_down(start, PUD_SIZE);
>> +	end = round_up(end, PUD_SIZE);
>> 	if (start >= end)
>> 		return;
>>
>> @@ -120,6 +120,7 @@ void initialize_identity_maps(void *rmode)
>> 	mapping_info.context = &pgt_data;
>> 	mapping_info.page_flag = __PAGE_KERNEL_LARGE_EXEC | sme_me_mask;
>> 	mapping_info.kernpg_flag = _KERNPG_TABLE;
>> +	mapping_info.direct_gbpages = true;
>>
>> 	/*
>> 	 * It should be impossible for this not to already be true,
>> @@ -365,8 +366,8 @@ void do_boot_page_fault(struct pt_regs *regs, unsigned long error_code)
>>
>> 	ghcb_fault = sev_es_check_ghcb_fault(address);
>>
>> -	address   &= PMD_MASK;
>> -	end        = address + PMD_SIZE;
>> +	address   &= PUD_MASK;
>> +	end        = address + PUD_SIZE;
>>
>> 	/*
>> 	 * Check for unexpected error codes. Unexpected are:
> Strong NAK: 1G pages are not supported by all 64-bit CPUs, *and* by your own admission breaks things ...
>
I strongly suspected that this was a no-go. Thank you for taking a 
looking and confirming it. I'll look into alternative solutions.


Anthony