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Re: [RFC v2 PATCH 01/13] mm/shmem: Introduce F_SEAL_GUEST
From: |
Chao Peng |
Subject: |
Re: [RFC v2 PATCH 01/13] mm/shmem: Introduce F_SEAL_GUEST |
Date: |
Tue, 23 Nov 2021 22:33:53 +0800 |
User-agent: |
Mutt/1.9.4 (2018-02-28) |
On Tue, Nov 23, 2021 at 10:06:02AM +0100, Paolo Bonzini wrote:
> On 11/19/21 16:39, David Hildenbrand wrote:
> > > If qmeu can put all the guest memory in a memfd and not map it, then
> > > I'd also like to see that the IOMMU can use this interface too so we
> > > can have VFIO working in this configuration.
> >
> > In QEMU we usually want to (and must) be able to access guest memory
> > from user space, with the current design we wouldn't even be able to
> > temporarily mmap it -- which makes sense for encrypted memory only. The
> > corner case really is encrypted memory. So I don't think we'll see a
> > broad use of this feature outside of encrypted VMs in QEMU. I might be
> > wrong, most probably I am:)
>
> It's not _that_ crazy an idea, but it's going to be some work to teach KVM
> that it has to kmap/kunmap around all memory accesses.
>
> I think it's great that memfd hooks are usable by more than one subsystem,
> OTOH it's fair that whoever needs it does the work---and VFIO does not need
> it for confidential VMs, yet, so it should be fine for now to have a single
> user.
>
> On the other hand, as I commented already, the lack of locking in the
> register/unregister functions has to be fixed even with a single user.
> Another thing we can do already is change the guest_ops/guest_mem_ops to
> something like memfd_falloc_notifier_ops/memfd_pfn_ops, and the
> register/unregister functions to memfd_register/unregister_falloc_notifier.
I'm satisified with this naming ;)
>
> Chao, can you also put this under a new CONFIG such as "bool MEMFD_OPS", and
> select it from KVM?
Yes, reasonable.
>
> Thanks,
>
> Paolo
- Re: [RFC v2 PATCH 01/13] mm/shmem: Introduce F_SEAL_GUEST, (continued)
- Re: [RFC v2 PATCH 01/13] mm/shmem: Introduce F_SEAL_GUEST, Sean Christopherson, 2021/11/19
- Re: [RFC v2 PATCH 01/13] mm/shmem: Introduce F_SEAL_GUEST, Jason Gunthorpe, 2021/11/19
- Re: [RFC v2 PATCH 01/13] mm/shmem: Introduce F_SEAL_GUEST, Sean Christopherson, 2021/11/19
- Re: [RFC v2 PATCH 01/13] mm/shmem: Introduce F_SEAL_GUEST, Jason Gunthorpe, 2021/11/19
- Re: [RFC v2 PATCH 01/13] mm/shmem: Introduce F_SEAL_GUEST, Sean Christopherson, 2021/11/19
- Re: [RFC v2 PATCH 01/13] mm/shmem: Introduce F_SEAL_GUEST, Jason Gunthorpe, 2021/11/20
- Re: [RFC v2 PATCH 01/13] mm/shmem: Introduce F_SEAL_GUEST, Paolo Bonzini, 2021/11/23
- Re: [RFC v2 PATCH 01/13] mm/shmem: Introduce F_SEAL_GUEST,
Chao Peng <=
- Re: [RFC v2 PATCH 01/13] mm/shmem: Introduce F_SEAL_GUEST, David Hildenbrand, 2021/11/23
- Re: [RFC v2 PATCH 01/13] mm/shmem: Introduce F_SEAL_GUEST, Jason Gunthorpe, 2021/11/23
Re: [RFC v2 PATCH 01/13] mm/shmem: Introduce F_SEAL_GUEST, Paolo Bonzini, 2021/11/23
[RFC v2 PATCH 02/13] KVM: Add KVM_EXIT_MEMORY_ERROR exit, Chao Peng, 2021/11/19
[RFC v2 PATCH 03/13] KVM: Extend kvm_userspace_memory_region to support fd based memslot, Chao Peng, 2021/11/19
[RFC v2 PATCH 04/13] KVM: Add fd-based memslot data structure and utils, Chao Peng, 2021/11/19
[RFC v2 PATCH 05/13] KVM: Implement fd-based memory using new memfd interfaces, Chao Peng, 2021/11/19
[RFC v2 PATCH 06/13] KVM: Register/unregister memfd backed memslot, Chao Peng, 2021/11/19