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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?Oa9x2sqs2y8BofV9H7oBFyi+kFbvfBqpQk5RA1NxT3Z5jDGVI/Wa1TxelPrN?= =?us-ascii?Q?1GOo6MQCNCpEfl7kJFQ/9QNxsWce9mh7+2bstWxX7o15hwPL9BObGw7sjvDe?= =?us-ascii?Q?9SQlmHpUzTWpMm4/HRLGHwPeHRMcJif0NCL6Xpud+NVEHPlQSefzZ7ZqYMvh?= =?us-ascii?Q?u9TeKvfpISr6OU8HTqL/1ghsqTe4PW0l+VB/++KSrnGG93LERDZsywRvDeie?= =?us-ascii?Q?3WsR/LeqD1zGXfWDh2o03AFM0EfJJ5P+PosMZt72RpUM8l52VD7CHX3fI/qQ?= =?us-ascii?Q?wXUkHYaTX4F0Sv8guUClPHwwOx0/tRADCCEJcxOk0RMyYEZBIVLvmcKkugN5?= =?us-ascii?Q?WLA9A6Uioj2Ka9eb91eVw2Ryeg1RkOz3tJfH8h3uZ+TYDXztfcedzv15Jm7x?= =?us-ascii?Q?YF+cU/ch41659XPb8QzFSkVI4EzyNqLW9fSToAC93ivxncV4Kmj7sHDk9dpu?= =?us-ascii?Q?FKWOryYRVAOm8aosW1S0gD4f5l9OuL7V4gQhdC6hbddb17BFOiPDV57Skqho?= =?us-ascii?Q?Xq351xuh9At59krRwWWc9LApnZVMHwO3+b9MOUkSyUS7gd1Qr0eVQPn5WbIC?= =?us-ascii?Q?IH8J8QoMyLaqB4/IJ9zjl9SkfNF1uQ0GSB47pfOPL5cF/YA+XZO6fzfSOV5E?= =?us-ascii?Q?ltSEE8KI1AxUVJwp3rBAB32BHY0jsigFfx8h36f4F/+2ThPJfy8xR29deZGz?= =?us-ascii?Q?MKV90OHkfulPqMY4vYEC/Vus9obpnet/pAl8Gr+rQS91hsUAP/hrELeiYaY7?= =?us-ascii?Q?t45w5tnk7zJ9Mbwx2mZyO0OBFTvgxoNoXR6wma+vZP93a0CcS9zxikklgcOw?= =?us-ascii?Q?AkRJub4lTtiGUM2IjJR/MJHqIcM78SNMy9DYhQA8UVEkN1NOlEFklDrKC/jF?= =?us-ascii?Q?gKu5sJFcaFV6fiyDQkTjgYM32TcgMILZ2TtN4sBE44yqIs7tp8MN0EmnjzK4?= =?us-ascii?Q?IlFKSYhGbi2nst01OJJAuN5imcfysGFvmdM74vhUjUuAQYS9AcAhSGQX8X8t?= =?us-ascii?Q?qZsJZ3nWJ48mNOcLkW25piZtNC1ZYOolrZRLhfIxSc2344Leh9i/XipsWHHO?= =?us-ascii?Q?vjIpC3EmRyD3iQ6cYoj3AtNMyM4150JyvJQn/yjnQXkhqcRs0F2lSoxDIjEd?= =?us-ascii?Q?Xbr/6ir7tOPcW6AZOgkojZjcRAWu3LcaP7Kiym6tEsWZSQCF+o6LCEatgp7n?= =?us-ascii?Q?kn8/yMKZHrwFtXQWxy5O4Xl5P8HqWdCNo0L7eqW7PFHBZO4iMnjwpPX3iOlD?= =?us-ascii?Q?LRYR5plPN31a6cgPn/2XvSSQtvqAFEMuwybn7Y+D5beceuDhQUYMIaBtYkNz?= =?us-ascii?Q?8a+bfd5jRU05z30ICXT/ztN5Awb96pkiCi726iPh0sXFb4LtecCcqXjh77+s?= =?us-ascii?Q?5xce2d9ZCehTVoGswaeoyr/WmbdqsE52JlRjEH2275wcxyjsU78wc33q916G?= =?us-ascii?Q?QSnfFuR81ydY+mLMzNTuBevVL3P5cOP6QeF0ofjkhg2UXSeW9VnfWhqRMuhm?= =?us-ascii?Q?eVYP3V/+4Gwd5dq0vWUcz0ZDvqXVOzZNUVVtUPb12bSIDxDXgZZquFhdYWYv?= =?us-ascii?Q?TTG/1yYNOcczdMC32Dk=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: c8507a99-ff1a-4c50-d87e-08ddf0828267 X-MS-Exchange-CrossTenant-AuthSource: PH7PR12MB5757.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Sep 2025 15:55:48.2058 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: WkNeXBh2gzC1m+p3UUelpPsnRmb1I9ty0dWTY6xx4XvTkkvnWL7oyIjTb9RY2Imm X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR12MB9513 On Wed, Sep 10, 2025 at 05:52:04PM +0200, Pratyush Yadav wrote: > On Wed, Sep 10 2025, Matthew Wilcox wrote: > > > On Wed, Sep 10, 2025 at 05:34:40PM +0200, Pratyush Yadav wrote: > >> +#define KHO_PAGE_MAGIC 0x4b484f50U /* ASCII for 'KHOP' */ > >> + > >> +/* > >> + * KHO uses page->private, which is an unsigned long, to store page metadata. > >> + * Use it to store both the magic and the order. > >> + */ > >> +union kho_page_info { > >> + unsigned long page_private; > >> + struct { > >> + unsigned int order; > >> + unsigned int magic; > >> + }; > > > > KHO is only supported on 64-bit? > > Yes. Currently only x86_64 and ARM64. It is mainly for hypervisor live > update so there isn't much reason to support it on 32-bit platforms. Presumably this will eventually change to use some special coding on the memdesc pointer? > >> @@ -210,16 +226,16 @@ static void kho_restore_page(struct page *page, unsigned int order) > >> struct folio *kho_restore_folio(phys_addr_t phys) > >> { > >> struct page *page = pfn_to_online_page(PHYS_PFN(phys)); > >> - unsigned long order; > >> + union kho_page_info info; > >> > >> if (!page) > >> return NULL; > >> > >> - order = page->private; > >> - if (order > MAX_PAGE_ORDER) > >> + info.page_private = page->private; > >> + if (info.magic != KHO_PAGE_MAGIC || info.order > MAX_PAGE_ORDER) All the impossible checks shoudl be WARN_ON() > >> return NULL; > >> > >> - kho_restore_page(page, order); > >> + kho_restore_page(page, info.order); > >> return page_folio(page); > > > > This all looks very confused. Before your patch as well as after it. > > I don't see anything in the current KHO code that requires the > > phys_addr_t to be order-aligned. > > Right, good point. I can send that as a follow up patch. But I think > this patch stands on its own without that fix too. Maybe it is worth adding some KHO_DEBUG kconfig to protect some of these extra checks? phys should be pfn_valid, phys should be aligned, the page should be in the right state, order should be valid, etc. All worth checking. Jason