Messages in this thread | | | Date | Mon, 26 Sep 2022 08:38:34 -0500 | Subject | Re: [PATCHv7 02/14] mm: Add support for unaccepted memory | From | Tom Lendacky <> |
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On 9/26/22 07:10, Kirill A. Shutemov wrote: > On Sat, Sep 24, 2022 at 04:03:02AM +0300, Kirill A. Shutemov wrote: >> On Thu, Sep 22, 2022 at 09:31:12AM -0500, Tom Lendacky wrote: >>> On 9/8/22 14:28, Mike Rapoport wrote: >>>> On Thu, Sep 08, 2022 at 09:23:07AM -0700, Dionna Amalie Glaze wrote: >>>>>> >>>>>> Looks like the first access to the memory map fails, although I think >>>>>> it's not in INIT_LIST_HEAD() but rather in init_page_count(). >>>>>> >>>>>> I'd start with making sure that page_alloc::memmap_alloc() actually returns >>>>>> accepted memory. If you build kernel with CONFIG_DEBUG_VM=y the memory map >>>>>> will poisoned in this function, so my guess is it'd crash there. >>>>>> >>>>> >>>>> That's a wonderful hint, thank you! I did not run this test >>>>> CONFIG_DEBUG_VM set, but you think it's possible it could still be >>>>> here? >>>> >>>> It depends on how you configured your kernel. Say, defconfig does not set >>>> it. >>>> >>> >>> I also hit the issue at 256GB. My config is using CONFIG_SPARSEMEM_VMEMMAP >>> and fails in memmap_init_range() when attempting to add the first PFN. It >>> looks like the underlying page that is backing the vmemmap has not been >>> accepted (I receive a #VC 0x404 => page not validated). >>> >>> Kirill, is this a path that you've looked at? It would appear that somewhere >>> in the vmemmap_populate_hugepages() path, some memory acceptance needs to be >>> done for the pages that are used to back vmemmap. I'm not very familiar with >>> this code, so I'm not sure why everything works for a guest with 255GB of >>> memory, but then fails for a guest with 256GB of memory. >> >> Hm. I don't have machine that large at hands at the moment. And I have not >> looked at the codepath before. >> >> I will try to look into the issue. > > I'm not able to trigger the bug. > > With help of vm.overcommit_memory=1, I was managed boot TDX guest to shell > with 256G and 1T of guest memory just fine. > > Any chance it is SEV-SNP specific?
There's always a chance. I'll do some more tracing and see what I can find to try and be certain.
> > Or maybe there some difference in kernel config? Could you share yours?
Yes, I'll send that to you off-list.
Thanks, Tom
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