From: Chao Peng <chao.p.peng@linux.intel.com>
To: Sean Christopherson <seanjc@google.com>
Cc: Wei Wang <wei.w.wang@linux.intel.com>,
"Gupta, Pankaj" <pankaj.gupta@amd.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-api@vger.kernel.org, linux-doc@vger.kernel.org,
qemu-devel@nongnu.org, linux-kselftest@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
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>,
Shuah Khan <shuah@kernel.org>, Mike Rapoport <rppt@kernel.org>,
Steven Price <steven.price@arm.com>,
"Maciej S . Szmigiero" <mail@maciej.szmigiero.name>,
Vlastimil Babka <vbabka@suse.cz>,
Vishal Annapurve <vannapurve@google.com>,
Yu Zhang <yu.c.zhang@linux.intel.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
luto@kernel.org, jun.nakajima@intel.com, dave.hansen@intel.com,
ak@linux.intel.com, david@redhat.com, aarcange@redhat.com,
ddutile@redhat.com, dhildenb@redhat.com,
Quentin Perret <qperret@google.com>,
Michael Roth <michael.roth@amd.com>,
mhocko@suse.com, Muchun Song <songmuchun@bytedance.com>
Subject: Re: [PATCH v7 11/14] KVM: Register/unregister the guest private memory regions
Date: Mon, 25 Jul 2022 21:04:17 +0800 [thread overview]
Message-ID: <20220725130417.GA304216@chaop.bj.intel.com> (raw)
In-Reply-To: <YtmT2irvgInX1kPp@google.com>
On Thu, Jul 21, 2022 at 05:58:50PM +0000, Sean Christopherson wrote:
> On Thu, Jul 21, 2022, Chao Peng wrote:
> > On Thu, Jul 21, 2022 at 03:34:59PM +0800, Wei Wang wrote:
> > >
> > >
> > > On 7/21/22 00:21, Sean Christopherson wrote:
> > > Maybe you could tag it with cgs for all the confidential guest support
> > > related stuff: e.g. kvm_vm_ioctl_set_cgs_mem()
> > >
> > > bool is_private = ioctl == KVM_MEMORY_ENCRYPT_REG_REGION;
> > > ...
> > > kvm_vm_ioctl_set_cgs_mem(, is_private)
> >
> > If we plan to widely use such abbr. through KVM (e.g. it's well known),
> > I'm fine.
>
> I'd prefer to stay away from "confidential guest", and away from any VM-scoped
> name for that matter. User-unmappable memmory has use cases beyond hiding guest
> state from the host, e.g. userspace could use inaccessible/unmappable memory to
> harden itself against unintentional access to guest memory.
>
> > I actually use mem_attr in patch: https://lkml.org/lkml/2022/7/20/610
> > But I also don't quite like it, it's so generic and sounds say nothing.
> >
> > But I do want a name can cover future usages other than just
> > private/shared (pKVM for example may have a third state).
>
> I don't think there can be a third top-level state. Memory is either private to
> the guest or it's not. There can be sub-states, e.g. memory could be selectively
> shared or encrypted with a different key, in which case we'd need metadata to
> track that state.
>
> Though that begs the question of whether or not private_fd is the correct
> terminology. E.g. if guest memory is backed by a memfd that can't be mapped by
> userspace (currently F_SEAL_INACCESSIBLE), but something else in the kernel plugs
> that memory into a device or another VM, then arguably that memory is shared,
> especially the multi-VM scenario.
>
> For TDX and SNP "private vs. shared" is likely the correct terminology given the
> current specs, but for generic KVM it's probably better to align with whatever
> terminology is used for memfd. "inaccessible_fd" and "user_inaccessible_fd" are
> a bit odd since the fd itself is accesible.
>
> What about "user_unmappable"? E.g.
>
> F_SEAL_USER_UNMAPPABLE, MFD_USER_UNMAPPABLE, KVM_HAS_USER_UNMAPPABLE_MEMORY,
> MEMFILE_F_USER_INACCESSIBLE, user_unmappable_fd, etc...
For KVM I also think user_unmappable looks better than 'private', e.g.
user_unmappable_fd/KVM_HAS_USER_UNMAPPABLE_MEMORY sounds more
appropriate names. For memfd however, I don't feel that strong to change
it from current 'inaccessible' to 'user_unmappable', one of the reason
is it's not just about unmappable, but actually also inaccessible
through direct ioctls like read()/write().
>
> that gives us flexibility to map the memory from within the kernel, e.g. into
> other VMs or devices.
>
> Hmm, and then keep your original "mem_attr_array" name? And probably
>
> int kvm_vm_ioctl_set_mem_attr(struct kvm *kvm, gpa_t gpa, gpa_t size,
> bool is_user_mappable)
>
> Then the x86/mmu code for TDX/SNP private faults could be:
>
> is_private = !kvm_is_gpa_user_mappable();
>
> if (fault->is_private != is_private) {
>
> or if we want to avoid mixing up "user_mappable" and "user_unmappable":
>
> is_private = kvm_is_gpa_user_unmappable();
>
> if (fault->is_private != is_private) {
>
> though a helper that returns a negative (not mappable) feels kludgy. And I like
> kvm_is_gpa_user_mappable() because then when there's not "special" memory, it
> defaults to true, which is more intuitive IMO.
yes.
>
> And then if the future needs more precision, e.g. user-unmappable memory isn't
> necessarily guest-exclusive, the uAPI names still work even though KVM internals
> will need to be reworked, but that's unavoidable. E.g. piggybacking
> KVM_MEMORY_ENCRYPT_(UN)REG_REGION doesn't allow for further differentiation,
> so we'd need to _extend_ the uAPI, but the _existing_ uAPI would still be sane.
Right, that has to be extended.
Chao
next prev parent reply other threads:[~2022-07-25 13:09 UTC|newest]
Thread overview: 172+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-06 8:20 [PATCH v7 00/14] KVM: mm: fd-based approach for supporting KVM guest private memory Chao Peng
2022-07-06 8:20 ` [PATCH v7 01/14] mm: Add F_SEAL_AUTO_ALLOCATE seal to memfd Chao Peng
2022-07-21 9:44 ` David Hildenbrand
2022-07-21 9:50 ` David Hildenbrand
2022-07-21 15:05 ` Sean Christopherson
2022-07-25 13:46 ` Chao Peng
2022-07-21 10:27 ` Gupta, Pankaj
2022-07-25 13:54 ` Chao Peng
2022-07-25 14:49 ` Gupta, Pankaj
2022-07-25 13:42 ` Chao Peng
2022-08-05 17:55 ` Paolo Bonzini
2022-08-05 18:06 ` David Hildenbrand
2022-08-10 9:40 ` Chao Peng
2022-08-10 9:38 ` Chao Peng
2022-08-17 23:41 ` Kirill A. Shutemov
2022-08-18 9:09 ` Paolo Bonzini
2022-08-23 7:36 ` David Hildenbrand
2022-08-24 10:20 ` Chao Peng
2022-08-26 15:19 ` Fuad Tabba
2022-08-29 15:18 ` Chao Peng
2022-07-06 8:20 ` [PATCH v7 02/14] selftests/memfd: Add tests for F_SEAL_AUTO_ALLOCATE Chao Peng
2022-08-05 13:11 ` David Hildenbrand
2022-07-06 8:20 ` [PATCH v7 03/14] mm: Introduce memfile_notifier Chao Peng
2022-08-05 13:22 ` David Hildenbrand
2022-08-10 9:22 ` Chao Peng
2022-08-10 10:05 ` David Hildenbrand
2022-08-10 14:38 ` Sean Christopherson
2022-08-11 12:27 ` Quentin Perret
2022-08-11 13:39 ` Chao Peng
2022-07-06 8:20 ` [PATCH v7 04/14] mm/shmem: Support memfile_notifier Chao Peng
2022-07-12 18:02 ` Gupta, Pankaj
2022-07-13 7:44 ` Chao Peng
2022-07-13 10:01 ` Gupta, Pankaj
2022-07-13 23:49 ` Chao Peng
2022-07-14 4:15 ` Gupta, Pankaj
2022-08-05 13:26 ` David Hildenbrand
2022-08-10 9:25 ` Chao Peng
2022-07-06 8:20 ` [PATCH v7 05/14] mm/memfd: Introduce MFD_INACCESSIBLE flag Chao Peng
2022-08-05 13:28 ` David Hildenbrand
2022-08-10 9:37 ` Chao Peng
2022-08-10 9:55 ` David Hildenbrand
2022-08-11 13:17 ` Chao Peng
2022-09-07 16:18 ` Kirill A. Shutemov
2022-07-06 8:20 ` [PATCH v7 06/14] KVM: Rename KVM_PRIVATE_MEM_SLOTS to KVM_INTERNAL_MEM_SLOTS Chao Peng
2022-07-06 8:20 ` [PATCH v7 07/14] KVM: Use gfn instead of hva for mmu_notifier_retry Chao Peng
2022-07-15 11:36 ` Gupta, Pankaj
2022-07-18 13:29 ` Chao Peng
2022-07-18 15:26 ` Sean Christopherson
2022-07-19 14:02 ` Chao Peng
2022-08-04 7:10 ` Isaku Yamahata
2022-08-10 8:19 ` Chao Peng
2022-07-06 8:20 ` [PATCH v7 08/14] KVM: Rename mmu_notifier_* Chao Peng
2022-07-29 19:02 ` Sean Christopherson
2022-08-03 10:13 ` Chao Peng
2022-08-05 19:54 ` Paolo Bonzini
2022-08-10 8:09 ` Chao Peng
2023-05-23 7:19 ` Kautuk Consul
2023-05-23 14:19 ` Sean Christopherson
2023-05-24 6:12 ` Kautuk Consul
2023-05-24 20:16 ` Sean Christopherson
2023-05-24 20:33 ` Peter Zijlstra
2023-05-24 21:39 ` Sean Christopherson
2023-05-25 8:54 ` Peter Zijlstra
2023-05-25 3:52 ` Kautuk Consul
2023-05-24 20:28 ` Peter Zijlstra
2022-07-06 8:20 ` [PATCH v7 09/14] KVM: Extend the memslot to support fd-based private memory Chao Peng
2022-07-29 19:51 ` Sean Christopherson
2022-08-03 10:08 ` Chao Peng
2022-08-03 14:42 ` Sean Christopherson
2022-07-06 8:20 ` [PATCH v7 10/14] KVM: Add KVM_EXIT_MEMORY_FAULT exit Chao Peng
2022-07-06 8:20 ` [PATCH v7 11/14] KVM: Register/unregister the guest private memory regions Chao Peng
2022-07-19 8:00 ` Gupta, Pankaj
2022-07-19 14:08 ` Chao Peng
2022-07-19 14:23 ` Gupta, Pankaj
2022-07-20 15:07 ` Chao Peng
2022-07-20 15:31 ` Gupta, Pankaj
2022-07-20 16:21 ` Sean Christopherson
2022-07-20 17:41 ` Gupta, Pankaj
2022-07-21 7:34 ` Wei Wang
2022-07-21 9:29 ` Chao Peng
2022-07-21 17:58 ` Sean Christopherson
2022-07-25 13:04 ` Chao Peng [this message]
2022-07-29 19:54 ` Sean Christopherson
2022-08-02 0:49 ` Sean Christopherson
2022-08-02 16:38 ` Sean Christopherson
2022-08-03 9:48 ` Chao Peng
2022-08-03 15:51 ` Sean Christopherson
2022-08-04 7:58 ` Chao Peng
2022-07-20 16:44 ` Sean Christopherson
2022-07-21 9:37 ` Chao Peng
2022-08-19 19:37 ` Vishal Annapurve
2022-08-24 10:37 ` Chao Peng
2022-08-26 15:19 ` Fuad Tabba
2022-08-29 15:21 ` Chao Peng
2022-07-06 8:20 ` [PATCH v7 12/14] KVM: Handle page fault for private memory Chao Peng
2022-07-29 20:58 ` Sean Christopherson
2022-08-03 9:52 ` Chao Peng
2022-07-06 8:20 ` [PATCH v7 13/14] KVM: Enable and expose KVM_MEM_PRIVATE Chao Peng
2022-07-19 9:55 ` Gupta, Pankaj
2022-07-19 14:12 ` Chao Peng
2022-07-06 8:20 ` [PATCH v7 14/14] memfd_create.2: Describe MFD_INACCESSIBLE flag Chao Peng
2022-08-01 14:40 ` Dave Hansen
2022-08-03 9:53 ` Chao Peng
2022-07-13 3:58 ` [PATCH v7 00/14] KVM: mm: fd-based approach for supporting KVM guest private memory Gupta, Pankaj
2022-07-13 7:57 ` Chao Peng
2022-07-13 10:35 ` Gupta, Pankaj
2022-07-13 23:59 ` Chao Peng
2022-07-14 4:39 ` Gupta, Pankaj
2022-07-14 5:06 ` Gupta, Pankaj
2022-07-14 4:29 ` Andy Lutomirski
2022-07-14 5:13 ` Gupta, Pankaj
2022-08-11 10:02 ` Nikunj A. Dadhania
2022-08-11 11:30 ` Gupta, Pankaj
2022-08-11 13:32 ` Chao Peng
2022-08-11 17:28 ` Nikunj A. Dadhania
2022-08-12 3:22 ` Nikunj A. Dadhania
2022-08-11 17:18 ` Nikunj A. Dadhania
2022-08-11 23:02 ` Gupta, Pankaj
2022-08-12 6:02 ` Gupta, Pankaj
2022-08-12 7:18 ` Gupta, Pankaj
2022-08-12 8:48 ` Nikunj A. Dadhania
2022-08-12 9:33 ` Gupta, Pankaj
2022-08-15 13:04 ` Chao Peng
2022-08-16 4:28 ` Nikunj A. Dadhania
2022-08-16 11:33 ` Gupta, Pankaj
2022-08-16 12:24 ` Kirill A . Shutemov
2022-08-16 13:03 ` Gupta, Pankaj
2022-08-16 15:38 ` Sean Christopherson
2022-08-17 15:27 ` Michael Roth
2022-08-23 1:25 ` Isaku Yamahata
2022-08-23 17:41 ` Gupta, Pankaj
2022-08-18 5:40 ` Hugh Dickins
2022-08-18 13:24 ` Kirill A . Shutemov
2022-08-19 0:20 ` Sean Christopherson
2022-08-19 3:38 ` Hugh Dickins
2022-08-19 22:53 ` Sean Christopherson
2022-08-23 7:55 ` David Hildenbrand
2022-08-23 16:05 ` Sean Christopherson
2022-08-24 9:41 ` Chao Peng
2022-09-09 4:55 ` Andy Lutomirski
2022-08-19 3:00 ` Hugh Dickins
2022-08-20 0:27 ` Kirill A. Shutemov
2022-08-21 5:15 ` Hugh Dickins
2022-08-31 14:24 ` Kirill A . Shutemov
2022-09-02 10:27 ` Chao Peng
2022-09-02 12:30 ` Kirill A . Shutemov
2022-09-08 1:10 ` Kirill A. Shutemov
2022-09-13 9:44 ` Sean Christopherson
2022-09-13 13:28 ` Kirill A. Shutemov
2022-09-13 14:53 ` Sean Christopherson
2022-09-13 16:00 ` Kirill A. Shutemov
2022-09-13 16:12 ` Sean Christopherson
2022-09-09 4:48 ` Andy Lutomirski
2022-09-09 14:32 ` Kirill A . Shutemov
2022-09-09 19:11 ` Andy Lutomirski
2022-09-09 23:02 ` Kirill A . Shutemov
2022-08-21 10:27 ` Matthew Wilcox
2022-08-24 10:27 ` Chao Peng
2022-09-09 4:44 ` Andy Lutomirski
[not found] ` <diqzlej60z57.fsf@ackerleytng-cloudtop.c.googlers.com>
[not found] ` <20221202061347.1070246-2-chao.p.peng@linux.intel.com>
2023-04-13 15:25 ` Christian Brauner
2023-04-13 22:28 ` Sean Christopherson
2023-04-14 22:38 ` Ackerley Tng
2023-04-14 23:26 ` Sean Christopherson
2023-04-15 0:06 ` Sean Christopherson
2023-04-19 8:29 ` Christian Brauner
2023-04-20 0:49 ` Sean Christopherson
2023-04-20 8:35 ` Christian Brauner
2022-08-26 15:19 ` Fuad Tabba
2022-08-29 15:17 ` Chao Peng
2022-08-31 9:12 ` Fuad Tabba
2022-09-02 10:19 ` Chao Peng
2022-09-09 15:35 ` Michael Roth
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