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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