Messages in this thread | | | Date | Thu, 8 Sep 2022 21:44:44 -0700 | Subject | Re: [PATCH v7 00/14] KVM: mm: fd-based approach for supporting KVM guest private memory | From | Andy Lutomirski <> |
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On 8/18/22 06:24, Kirill A . Shutemov wrote: > On Wed, Aug 17, 2022 at 10:40:12PM -0700, Hugh Dickins wrote: >> On Wed, 6 Jul 2022, Chao Peng wrote: >>> This is the v7 of this series which tries to implement the fd-based KVM >>> guest private memory. >> >> Here at last are my reluctant thoughts on this patchset. >> >> fd-based approach for supporting KVM guest private memory: fine. >> >> Use or abuse of memfd and shmem.c: mistaken. >> >> memfd_create() was an excellent way to put together the initial prototype. >> >> But since then, TDX in particular has forced an effort into preventing >> (by flags, seals, notifiers) almost everything that makes it shmem/tmpfs. >> >> Are any of the shmem.c mods useful to existing users of shmem.c? No. >> Is MFD_INACCESSIBLE useful or comprehensible to memfd_create() users? No. >> >> What use do you have for a filesystem here? Almost none. >> IIUC, what you want is an fd through which QEMU can allocate kernel >> memory, selectively free that memory, and communicate fd+offset+length >> to KVM. And perhaps an interface to initialize a little of that memory >> from a template (presumably copied from a real file on disk somewhere). >> >> You don't need shmem.c or a filesystem for that! >> >> If your memory could be swapped, that would be enough of a good reason >> to make use of shmem.c: but it cannot be swapped; and although there >> are some references in the mailthreads to it perhaps being swappable >> in future, I get the impression that will not happen soon if ever. >> >> If your memory could be migrated, that would be some reason to use >> filesystem page cache (because page migration happens to understand >> that type of memory): but it cannot be migrated. > > Migration support is in pipeline. It is part of TDX 1.5 [1]. And swapping > theoretically possible, but I'm not aware of any plans as of now. > > [1] https://www.intel.com/content/www/us/en/developer/articles/technical/intel-trust-domain-extensions.html >
This thing?
https://cdrdv2.intel.com/v1/dl/getContent/733578
That looks like migration between computers, not between NUMA nodes. Or am I missing something?
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