Messages in this thread |  | | Date | Mon, 28 Nov 2022 09:43:04 +0100 | Subject | Re: [PATCH v7 10/20] x86/virt/tdx: Use all system memory when initializing TDX module as TDX memory | From | David Hildenbrand <> |
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On 28.11.22 09:38, Huang, Kai wrote: > On Fri, 2022-11-25 at 10:28 +0100, David Hildenbrand wrote: >> On 24.11.22 10:06, Huang, Kai wrote: >>> On Wed, 2022-11-23 at 17:50 -0800, Dan Williams wrote: >>>>> >>>>> @@ -968,6 +969,15 @@ int arch_add_memory(int nid, u64 start, u64 size, >>>>> unsigned long start_pfn = start >> PAGE_SHIFT; >>>>> unsigned long nr_pages = size >> PAGE_SHIFT; >>>>> >>>>> + /* >>>>> + * For now if TDX is enabled, all pages in the page allocator >>>>> + * must be TDX memory, which is a fixed set of memory regions >>>>> + * that are passed to the TDX module. Reject the new region >>>>> + * if it is not TDX memory to guarantee above is true. >>>>> + */ >>>>> + if (!tdx_cc_memory_compatible(start_pfn, start_pfn + nr_pages)) >>>>> + return -EINVAL; >>>> >>>> arch_add_memory() does not add memory to the page allocator. For >>>> example, memremap_pages() uses arch_add_memory() and explicitly does not >>>> release the memory to the page allocator. >>> >>> Indeed. Sorry I missed this. >>> >>>> This check belongs in >>>> add_memory_resource() to prevent new memory that violates TDX from being >>>> onlined. >>> >>> This would require adding another 'arch_cc_memory_compatible()' to the common >>> add_memory_resource() (I actually long time ago had such patch to work with the >>> memremap_pages() you mentioned above). >>> >>> How about adding a memory_notifier to the TDX code, and reject online of TDX >>> incompatible memory (something like below)? The benefit is this is TDX code >>> self contained and won't pollute the common mm code: >>> >>> +static int tdx_memory_notifier(struct notifier_block *nb, >>> + unsigned long action, void *v) >>> +{ >>> + struct memory_notify *mn = v; >>> + >>> + if (action != MEM_GOING_ONLINE) >>> + return NOTIFY_OK; >>> + >>> + /* >>> + * Not all memory is compatible with TDX. Reject >>> + * online of any incompatible memory. >>> + */ >>> + return tdx_cc_memory_compatible(mn->start_pfn, >>> + mn->start_pfn + mn->nr_pages) ? NOTIFY_OK : NOTIFY_BAD; >>> +} >>> + >>> +static struct notifier_block tdx_memory_nb = { >>> + .notifier_call = tdx_memory_notifier, >>> +}; >> >> With mhp_memmap_on_memory() some memory might already be touched during >> add_memory() (because part of the hotplug memory is used for holding the >> memmap), not when actually onlining memory. So in that case, this would >> be too late. > > Hi David, > > Thanks for the review! > > Right. The memmap pages are added to the zone before online_pages(), but IIUC > those memmap pages will never be free pages thus won't be allocated by the page > allocator, correct? Therefore in practice there won't be problem even they are > not TDX compatible memory.
But that memory will be read/written. Isn't that an issue, for example, if memory doesn't get accepted etc?
-- Thanks,
David / dhildenb
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