From: Sean Christopherson <seanjc@google.com>
To: Chao Peng <chao.p.peng@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>,
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, 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>,
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>,
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
Subject: Re: [PATCH v6 4/8] KVM: Extend the memslot to support fd-based private memory
Date: Fri, 10 Jun 2022 16:14:21 +0000 [thread overview]
Message-ID: <YqNt3Sgzge5Rph/R@google.com> (raw)
In-Reply-To: <20220530132613.GA1200843@chaop.bj.intel.com>
On Mon, May 30, 2022, Chao Peng wrote:
> On Mon, May 23, 2022 at 03:22:32PM +0000, Sean Christopherson wrote:
> > Actually, if the semantics are that userspace declares memory as private, then we
> > can reuse KVM_MEMORY_ENCRYPT_REG_REGION and KVM_MEMORY_ENCRYPT_UNREG_REGION. It'd
> > be a little gross because we'd need to slightly redefine the semantics for TDX, SNP,
> > and software-protected VM types, e.g. the ioctls() currently require a pre-exisitng
> > memslot. But I think it'd work...
>
> These existing ioctls looks good for TDX and probably SNP as well. For
> softrware-protected VM types, it may not be enough. Maybe for the first
> step we can reuse this for all hardware based solutions and invent new
> interface when software-protected solution gets really supported.
>
> There is semantics difference for fd-based private memory. Current above
> two ioctls() use userspace addreess(hva) while for fd-based it should be
> fd+offset, and probably it's better to use gpa in this case. Then we
> will need change existing semantics and break backward-compatibility.
My thought was to keep the existing semantics for VMs with type==0, i.e. SEV and
SEV-ES VMs. It's a bit gross, but the pinning behavior is a dead end for SNP and
TDX, so it effectively needs to be deprecated anyways. I'm definitely not opposed
to a new ioctl if Paolo or others think this is too awful, but burning an ioctl
for this seems wasteful.
Then generic KVM can do something like:
case KVM_MEMORY_ENCRYPT_REG_REGION:
case KVM_MEMORY_ENCRYPT_UNREG_REGION:
struct kvm_enc_region region;
if (!kvm_arch_vm_supports_private_memslots(kvm))
goto arch_vm_ioctl;
r = -EFAULT;
if (copy_from_user(®ion, argp, sizeof(region)))
goto out;
r = kvm_set_encrypted_region(ioctl, ®ion);
break;
default:
arch_vm_ioctl:
r = kvm_arch_vm_ioctl(filp, ioctl, arg);
where common KVM provides
__weak void kvm_arch_vm_supports_private_memslots(struct kvm *kvm)
{
return false;
}
and x86 overrides that to
bool kvm_arch_vm_supports_private_memslots(struct kvm *kvm)
{
/* I can't remember what we decided on calling type '0' VMs. */
return !!kvm->vm_type;
}
and if someone ever wants to enable private memslot for SEV/SEV-ES guests we can
always add a capability or even a new VM type.
pKVM on arm can then obviously implement kvm_arch_vm_supports_private_memslots()
to grab whatever identifies a pKVM VM.
next prev parent reply other threads:[~2022-06-10 16:14 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-19 15:37 [PATCH v6 0/8] KVM: mm: fd-based approach for supporting KVM guest private memory Chao Peng
2022-05-19 15:37 ` [PATCH v6 1/8] mm: Introduce memfile_notifier Chao Peng
2022-05-19 15:37 ` [PATCH v6 2/8] mm/shmem: Support memfile_notifier Chao Peng
2022-05-19 15:37 ` [PATCH v6 3/8] mm/memfd: Introduce MFD_INACCESSIBLE flag Chao Peng
2022-05-31 19:15 ` Vishal Annapurve
2022-06-01 10:17 ` Chao Peng
2022-06-01 12:11 ` Gupta, Pankaj
2022-06-02 10:07 ` Chao Peng
2022-06-14 20:23 ` Sean Christopherson
2022-06-15 8:53 ` Chao Peng
2022-05-19 15:37 ` [PATCH v6 4/8] KVM: Extend the memslot to support fd-based private memory Chao Peng
2022-05-20 17:57 ` Andy Lutomirski
2022-05-20 18:31 ` Sean Christopherson
2022-05-22 4:03 ` Andy Lutomirski
2022-05-23 13:21 ` Chao Peng
2022-05-23 15:22 ` Sean Christopherson
2022-05-30 13:26 ` Chao Peng
2022-06-10 16:14 ` Sean Christopherson [this message]
2022-06-14 6:45 ` Chao Peng
2022-06-23 22:59 ` Michael Roth
2022-06-24 8:54 ` Chao Peng
2022-06-24 13:01 ` Michael Roth
2022-06-17 20:52 ` Sean Christopherson
2022-06-17 21:27 ` Sean Christopherson
2022-06-20 14:09 ` Chao Peng
2022-06-20 14:08 ` Chao Peng
2022-05-19 15:37 ` [PATCH v6 5/8] KVM: Add KVM_EXIT_MEMORY_FAULT exit Chao Peng
2022-05-19 15:37 ` [PATCH v6 6/8] KVM: Handle page fault for private memory Chao Peng
2022-06-17 21:30 ` Sean Christopherson
2022-06-20 14:16 ` Chao Peng
2022-08-19 0:40 ` Kirill A. Shutemov
2022-08-25 23:43 ` Sean Christopherson
2022-06-24 3:58 ` Nikunj A. Dadhania
2022-06-24 9:02 ` Chao Peng
2022-06-30 19:14 ` Vishal Annapurve
2022-06-30 22:21 ` Michael Roth
2022-07-01 1:21 ` Xiaoyao Li
2022-07-07 20:08 ` Sean Christopherson
2022-07-08 3:29 ` Xiaoyao Li
2022-07-20 23:08 ` Vishal Annapurve
2022-07-21 9:45 ` Chao Peng
2022-05-19 15:37 ` [PATCH v6 7/8] KVM: Enable and expose KVM_MEM_PRIVATE Chao Peng
2022-06-23 22:07 ` Michael Roth
2022-06-24 8:43 ` Chao Peng
2022-05-19 15:37 ` [PATCH v6 8/8] memfd_create.2: Describe MFD_INACCESSIBLE flag Chao Peng
2022-06-06 20:09 ` [PATCH v6 0/8] KVM: mm: fd-based approach for supporting KVM guest private memory Vishal Annapurve
2022-06-07 6:57 ` Chao Peng
2022-06-08 0:55 ` Marc Orr
2022-06-08 2:18 ` Chao Peng
2022-06-08 19:37 ` Vishal Annapurve
2022-06-09 20:29 ` Sean Christopherson
2022-06-14 7:28 ` Chao Peng
2022-06-14 17:37 ` Andy Lutomirski
2022-06-14 19:08 ` Sean Christopherson
2022-06-14 20:59 ` Andy Lutomirski
2022-06-15 9:17 ` Chao Peng
2022-06-15 14:29 ` Sean Christopherson
2022-06-10 0:11 ` Marc Orr
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