From: Chao Peng <chao.p.peng@linux.intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: David Hildenbrand <david@redhat.com>,
Jason Gunthorpe <jgg@ziepe.ca>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
qemu-devel@nongnu.org, Jonathan Corbet <corbet@lwn.net>,
Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
Hugh Dickins <hughd@google.com>, Jeff Layton <jlayton@kernel.org>,
"J . Bruce Fields" <bfields@fieldses.org>,
Andrew Morton <akpm@linux-foundation.org>,
Yu Zhang <yu.c.zhang@linux.intel.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
luto@kernel.org, john.ji@intel.com, susie.li@intel.com,
jun.nakajima@intel.com, dave.hansen@intel.com,
ak@linux.intel.com
Subject: Re: [RFC v2 PATCH 01/13] mm/shmem: Introduce F_SEAL_GUEST
Date: Tue, 23 Nov 2021 22:33:53 +0800 [thread overview]
Message-ID: <20211123143353.GD32088@chaop.bj.intel.com> (raw)
In-Reply-To: <6de78894-8269-ea3a-b4ee-a5cc4dad827e@redhat.com>
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
next prev parent reply other threads:[~2021-11-23 14:34 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-19 13:47 [RFC v2 PATCH 00/13] KVM: mm: fd-based approach for supporting KVM guest private memory Chao Peng
2021-11-19 13:47 ` [RFC v2 PATCH 01/13] mm/shmem: Introduce F_SEAL_GUEST Chao Peng
2021-11-19 13:51 ` David Hildenbrand
2021-11-22 13:59 ` Kirill A. Shutemov
2021-11-19 15:19 ` Jason Gunthorpe
2021-11-19 15:39 ` David Hildenbrand
2021-11-19 16:00 ` Jason Gunthorpe
2021-11-22 9:26 ` David Hildenbrand
2021-11-22 13:31 ` Jason Gunthorpe
2021-11-22 13:35 ` David Hildenbrand
2021-11-22 14:01 ` Jason Gunthorpe
2021-11-22 14:57 ` David Hildenbrand
2021-11-22 15:09 ` Jason Gunthorpe
2021-11-22 15:15 ` David Hildenbrand
2021-11-19 19:18 ` Sean Christopherson
2021-11-19 19:47 ` Jason Gunthorpe
2021-11-19 22:21 ` Sean Christopherson
2021-11-19 23:33 ` Jason Gunthorpe
2021-11-20 1:23 ` Sean Christopherson
2021-11-21 0:05 ` Jason Gunthorpe
2021-11-23 9:06 ` Paolo Bonzini
2021-11-23 14:33 ` Chao Peng [this message]
2021-11-23 15:20 ` David Hildenbrand
2021-11-23 17:17 ` Jason Gunthorpe
2021-11-23 8:54 ` Paolo Bonzini
2021-12-03 1:11 ` Andy Lutomirski
2021-11-19 13:47 ` [RFC v2 PATCH 02/13] KVM: Add KVM_EXIT_MEMORY_ERROR exit Chao Peng
2021-11-19 13:47 ` [RFC v2 PATCH 03/13] KVM: Extend kvm_userspace_memory_region to support fd based memslot Chao Peng
2021-11-19 13:47 ` [RFC v2 PATCH 04/13] KVM: Add fd-based memslot data structure and utils Chao Peng
2021-11-23 8:41 ` Paolo Bonzini
2021-11-23 14:30 ` Chao Peng
2021-11-19 13:47 ` [RFC v2 PATCH 05/13] KVM: Implement fd-based memory using new memfd interfaces Chao Peng
2021-11-19 13:47 ` [RFC v2 PATCH 06/13] KVM: Register/unregister memfd backed memslot Chao Peng
2021-11-25 16:55 ` Steven Price
2021-11-19 13:47 ` [RFC v2 PATCH 07/13] KVM: Handle page fault for fd based memslot Chao Peng
2021-11-20 1:55 ` Yao Yuan
2021-11-22 9:18 ` Chao Peng
2021-11-19 13:47 ` [RFC v2 PATCH 08/13] KVM: Rename hva memory invalidation code to cover fd-based offset Chao Peng
2021-11-19 13:47 ` [RFC v2 PATCH 09/13] KVM: Introduce kvm_memfd_invalidate_range Chao Peng
2021-11-23 8:46 ` Paolo Bonzini
2021-11-23 14:24 ` Chao Peng
2021-11-19 13:47 ` [RFC v2 PATCH 10/13] KVM: Match inode for invalidation of fd-based slot Chao Peng
2021-11-19 13:47 ` [RFC v2 PATCH 11/13] KVM: Add kvm_map_gfn_range Chao Peng
2021-11-19 13:47 ` [RFC v2 PATCH 12/13] KVM: Introduce kvm_memfd_fallocate_range Chao Peng
2021-11-19 13:47 ` [RFC v2 PATCH 13/13] KVM: Enable memfd based page invalidation/fallocate Chao Peng
2021-11-22 14:16 ` Kirill A. Shutemov
2021-11-23 1:06 ` Chao Peng
2021-11-23 9:09 ` Paolo Bonzini
2021-11-23 15:00 ` Chao Peng
2021-11-23 8:51 ` Paolo Bonzini
2021-12-03 1:08 ` [RFC v2 PATCH 00/13] KVM: mm: fd-based approach for supporting KVM guest private memory Andy Lutomirski
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