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From: Eric van Tassell <evantass@amd.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>,
	Paolo Bonzini <pbonzini@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	eric van tassell <Eric.VanTassell@amd.com>,
	Tom Lendacky <thomas.lendacky@amd.com>
Subject: Re: [RFC PATCH 0/8] KVM: x86/mmu: Introduce pinned SPTEs framework
Date: Sun, 2 Aug 2020 22:00:13 -0500
Message-ID: <b5cc5643-4790-3c88-e767-1a7506afb2ae@amd.com> (raw)
In-Reply-To: <20200731212323.21746-1-sean.j.christopherson@intel.com>

Sean,
	What commit did you base your series  on?
	Thanks.

-evt(Eric van Tassell)

On 7/31/20 4:23 PM, Sean Christopherson wrote:
> SEV currently needs to pin guest memory as it doesn't support migrating
> encrypted pages.  Introduce a framework in KVM's MMU to support pinning
> pages on demand without requiring additional memory allocations, and with
> (somewhat hazy) line of sight toward supporting more advanced features for
> encrypted guest memory, e.g. host page migration.
> 
> The idea is to use a software available bit in the SPTE to track that a
> page has been pinned.  The decision to pin a page and the actual pinning
> managment is handled by vendor code via kvm_x86_ops hooks.  There are
> intentionally two hooks (zap and unzap) introduced that are not needed for
> SEV.  I included them to again show how the flag (probably renamed?) could
> be used for more than just pin/unpin.
> 
> Bugs in the core implementation are pretty much guaranteed.  The basic
> concept has been tested, but in a fairly different incarnation.  Most
> notably, tagging PRESENT SPTEs as PINNED has not been tested, although
> using the PINNED flag to track zapped (and known to be pinned) SPTEs has
> been tested.  I cobbled this variation together fairly quickly to get the
> code out there for discussion.
> 
> The last patch to pin SEV pages during sev_launch_update_data() is
> incomplete; it's there to show how we might leverage MMU-based pinning to
> support pinning pages before the guest is live.
> 
> Sean Christopherson (8):
>    KVM: x86/mmu: Return old SPTE from mmu_spte_clear_track_bits()
>    KVM: x86/mmu: Use bits 2:0 to check for present SPTEs
>    KVM: x86/mmu: Refactor handling of not-present SPTEs in mmu_set_spte()
>    KVM: x86/mmu: Add infrastructure for pinning PFNs on demand
>    KVM: SVM: Use the KVM MMU SPTE pinning hooks to pin pages on demand
>    KVM: x86/mmu: Move 'pfn' variable to caller of direct_page_fault()
>    KVM: x86/mmu: Introduce kvm_mmu_map_tdp_page() for use by SEV
>    KVM: SVM: Pin SEV pages in MMU during sev_launch_update_data()
> 
>   arch/x86/include/asm/kvm_host.h |   7 ++
>   arch/x86/kvm/mmu.h              |   3 +
>   arch/x86/kvm/mmu/mmu.c          | 186 +++++++++++++++++++++++++-------
>   arch/x86/kvm/mmu/paging_tmpl.h  |   3 +-
>   arch/x86/kvm/svm/sev.c          | 141 +++++++++++++++++++++++-
>   arch/x86/kvm/svm/svm.c          |   3 +
>   arch/x86/kvm/svm/svm.h          |   3 +
>   7 files changed, 302 insertions(+), 44 deletions(-)
> 

  parent reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-31 21:23 Sean Christopherson
2020-07-31 21:23 ` [RFC PATCH 1/8] KVM: x86/mmu: Return old SPTE from mmu_spte_clear_track_bits() Sean Christopherson
2020-07-31 21:23 ` [RFC PATCH 2/8] KVM: x86/mmu: Use bits 2:0 to check for present SPTEs Sean Christopherson
2020-07-31 21:23 ` [RFC PATCH 3/8] KVM: x86/mmu: Refactor handling of not-present SPTEs in mmu_set_spte() Sean Christopherson
2020-07-31 21:23 ` [RFC PATCH 4/8] KVM: x86/mmu: Add infrastructure for pinning PFNs on demand Sean Christopherson
2020-07-31 21:23 ` [RFC PATCH 5/8] KVM: SVM: Use the KVM MMU SPTE pinning hooks to pin pages " Sean Christopherson
2020-07-31 21:23 ` [RFC PATCH 6/8] KVM: x86/mmu: Move 'pfn' variable to caller of direct_page_fault() Sean Christopherson
2020-07-31 21:23 ` [RFC PATCH 7/8] KVM: x86/mmu: Introduce kvm_mmu_map_tdp_page() for use by SEV Sean Christopherson
2020-07-31 21:23 ` [RFC PATCH 8/8] KVM: SVM: Pin SEV pages in MMU during sev_launch_update_data() Sean Christopherson
2020-08-03  3:00 ` Eric van Tassell [this message]
2020-08-03 15:00   ` [RFC PATCH 0/8] KVM: x86/mmu: Introduce pinned SPTEs framework Sean Christopherson
2020-08-03 15:52 ` Brijesh Singh
2020-08-03 17:16   ` Sean Christopherson
2020-08-04 19:40     ` Brijesh Singh

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