From: "Tian, Kevin" <kevin.tian@intel.com>
To: "Lutomirski, Andy" <luto@kernel.org>,
Yu Zhang <yu.c.zhang@linux.intel.com>,
David Hildenbrand <david@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm list <kvm@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Borislav Petkov <bp@alien8.de>,
Andrew Morton <akpm@linux-foundation.org>,
Joerg Roedel <jroedel@suse.de>, Andi Kleen <ak@linux.intel.com>,
David Rientjes <rientjes@google.com>,
Vlastimil Babka <vbabka@suse.cz>,
Tom Lendacky <thomas.lendacky@amd.com>,
Thomas Gleixner <tglx@linutronix.de>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
"Ingo Molnar" <mingo@redhat.com>,
Varad Gautam <varad.gautam@suse.com>,
"Dario Faggioli" <dfaggioli@suse.com>,
the arch/x86 maintainers <x86@kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-coco@lists.linux.dev" <linux-coco@lists.linux.dev>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
Sathyanarayanan Kuppuswamy
<sathyanarayanan.kuppuswamy@linux.intel.com>,
"Hansen, Dave" <dave.hansen@intel.com>
Subject: RE: [RFC] KVM: mm: fd-based approach for supporting KVM guest private memory
Date: Wed, 1 Sep 2021 07:12:22 +0000 [thread overview]
Message-ID: <BN9PR11MB5433876DE6B6B92F9B50E3A58CCD9@BN9PR11MB5433.namprd11.prod.outlook.com> (raw)
In-Reply-To: <8f3630ff-bd6d-4d57-8c67-6637ea2c9560@www.fastmail.com>
> From: Andy Lutomirski <luto@kernel.org>
> Sent: Wednesday, September 1, 2021 12:53 PM
>
> On Thu, Aug 26, 2021, at 7:31 PM, Yu Zhang wrote:
> > On Thu, Aug 26, 2021 at 12:15:48PM +0200, David Hildenbrand wrote:
>
> > Thanks a lot for this summary. A question about the requirement: do we or
> > do we not have plan to support assigned device to the protected VM?
> >
> > If yes. The fd based solution may need change the VFIO interface as well(
> > though the fake swap entry solution need mess with VFIO too). Because:
> >
> > 1> KVM uses VFIO when assigning devices into a VM.
> >
> > 2> Not knowing which GPA ranges may be used by the VM as DMA buffer,
> all
> > guest pages will have to be mapped in host IOMMU page table to host
> pages,
> > which are pinned during the whole life cycle fo the VM.
> >
> > 3> IOMMU mapping is done during VM creation time by VFIO and IOMMU
> driver,
> > in vfio_dma_do_map().
> >
> > 4> However, vfio_dma_do_map() needs the HVA to perform a GUP to get
> the HPA
> > and pin the page.
> >
> > But if we are using fd based solution, not every GPA can have a HVA, thus
> > the current VFIO interface to map and pin the GPA(IOVA) wont work. And I
> > doubt if VFIO can be modified to support this easily.
> >
> >
>
> Do you mean assigning a normal device to a protected VM or a hypothetical
> protected-MMIO device?
>
> If the former, it should work more or less like with a non-protected VM.
> mmap the VFIO device, set up a memslot, and use it. I'm not sure whether
> anyone will actually do this, but it should be possible, at least in principle.
> Maybe someone will want to assign a NIC to a TDX guest. An NVMe device
> with the understanding that the guest can't trust it wouldn't be entirely crazy
> ether.
>
> If the latter, AFAIK there is no spec for how it would work even in principle.
> Presumably it wouldn't work quite like VFIO -- instead, the kernel could have
> a protection-virtual-io-fd mechanism, and that fd could be bound to a
> memslot in whatever way we settle on for binding secure memory to a
> memslot.
FYI the iommu logic in VFIO is being refactored out into an unified /dev/iommu
framework [1]. Currently it plans to support the same DMA mapping semantics
as what VFIO provides today (HVA-based). in the future it could be extended
to support another mapping protocol which accepts fd+offset instead of HVA
and then calls the helper function from whatever backing store which can help
translate fd+offset to HPA instead of using GUP.
Thanks
Kevin
[1]https://lore.kernel.org/kvm/BN9PR11MB5433B1E4AE5B0480369F97178C189@BN9PR11MB5433.namprd11.prod.outlook.com/
next prev parent reply other threads:[~2021-09-01 7:12 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-24 0:52 [RFC] KVM: mm: fd-based approach for supporting KVM guest private memory Sean Christopherson
2021-08-24 10:48 ` Yu Zhang
2021-08-26 0:35 ` Sean Christopherson
2021-08-26 13:23 ` Yu Zhang
2021-08-26 10:15 ` David Hildenbrand
2021-08-26 17:05 ` Andy Lutomirski
2021-08-26 21:26 ` David Hildenbrand
2021-08-27 18:24 ` Andy Lutomirski
2021-08-27 22:28 ` Sean Christopherson
2021-08-31 19:12 ` David Hildenbrand
2021-08-31 20:45 ` Sean Christopherson
2021-09-01 7:51 ` David Hildenbrand
2021-08-27 2:31 ` Yu Zhang
2021-08-31 19:08 ` David Hildenbrand
2021-08-31 20:01 ` Andi Kleen
2021-08-31 20:15 ` David Hildenbrand
2021-08-31 20:39 ` Andi Kleen
2021-09-01 3:34 ` Yu Zhang
2021-09-01 4:53 ` Andy Lutomirski
2021-09-01 7:12 ` Tian, Kevin [this message]
2021-09-01 10:24 ` Yu Zhang
2021-09-01 16:07 ` Andy Lutomirski
2021-09-01 16:27 ` David Hildenbrand
2021-09-02 8:34 ` Yu Zhang
2021-09-02 8:44 ` David Hildenbrand
2021-09-02 11:02 ` Yu Zhang
2021-09-02 8:19 ` Yu Zhang
2021-09-02 18:41 ` Andy Lutomirski
2021-09-07 1:33 ` Yan Zhao
2021-09-02 9:27 ` Joerg Roedel
2021-09-02 18:41 ` Andy Lutomirski
2021-09-02 18:57 ` Sean Christopherson
2021-09-02 19:07 ` Dave Hansen
2021-09-02 20:42 ` Andy Lutomirski
2021-08-27 22:18 ` Sean Christopherson
2021-08-31 19:07 ` David Hildenbrand
2021-08-31 21:54 ` Sean Christopherson
2021-09-01 8:09 ` David Hildenbrand
2021-09-01 15:54 ` Andy Lutomirski
2021-09-01 16:16 ` David Hildenbrand
2021-09-01 17:09 ` Andy Lutomirski
2021-09-01 16:18 ` James Bottomley
2021-09-01 16:22 ` David Hildenbrand
2021-09-01 16:31 ` James Bottomley
2021-09-01 16:37 ` David Hildenbrand
2021-09-01 16:45 ` James Bottomley
2021-09-01 17:08 ` David Hildenbrand
2021-09-01 17:50 ` Sean Christopherson
2021-09-01 17:53 ` David Hildenbrand
2021-09-01 17:08 ` Andy Lutomirski
2021-09-01 17:13 ` James Bottomley
2021-09-02 10:18 ` Joerg Roedel
2021-09-01 18:24 ` Andy Lutomirski
2021-09-01 19:26 ` Dave Hansen
2021-09-07 15:00 ` Tom Lendacky
2021-09-01 4:58 ` Andy Lutomirski
2021-09-01 7:49 ` David Hildenbrand
2021-09-02 18:47 ` Kirill A. Shutemov
2021-09-02 20:33 ` Sean Christopherson
2021-09-03 19:14 ` Kirill A. Shutemov
2021-09-03 19:15 ` Andy Lutomirski
2021-09-10 17:18 ` Kirill A. Shutemov
2021-09-15 19:58 ` Chao Peng
2021-09-15 13:51 ` David Hildenbrand
2021-09-15 14:29 ` Kirill A. Shutemov
2021-09-15 14:59 ` David Hildenbrand
2021-09-15 15:35 ` David Hildenbrand
2021-09-15 20:04 ` Kirill A. Shutemov
2021-09-15 14:11 ` Kirill A. Shutemov
2021-09-16 7:36 ` Chao Peng
2021-09-16 9:24 ` Paolo Bonzini
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