From: Sean Christopherson <seanjc@google.com>
To: "Nikunj A. Dadhania" <nikunj@amd.com>
Cc: 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>,
Brijesh Singh <brijesh.singh@amd.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
Peter Gonda <pgonda@google.com>, Bharata B Rao <bharata@amd.com>,
"Maciej S . Szmigiero" <mail@maciej.szmigiero.name>,
Mingwei Zhang <mizhang@google.com>,
David Hildenbrand <david@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC v1 0/9] KVM: SVM: Defer page pinning for SEV guests
Date: Wed, 30 Mar 2022 19:47:33 +0000 [thread overview]
Message-ID: <YkSz1R3YuFszcZrY@google.com> (raw)
In-Reply-To: <c4b33753-01d7-684e-23ac-1189bd217761@amd.com>
On Wed, Mar 30, 2022, Nikunj A. Dadhania wrote:
> On 3/29/2022 2:30 AM, Sean Christopherson wrote:
> > Let me preface this by saying I generally like the idea and especially the
> > performance, but...
> >
> > I think we should abandon this approach in favor of committing all our resources
> > to fd-based private memory[*], which (if done right) will provide on-demand pinning
> > for "free".
>
> I will give this a try for SEV, was on my todo list.
>
> > I would much rather get that support merged sooner than later, and use
> > it as a carrot for legacy SEV to get users to move over to its new APIs, with a long
> > term goal of deprecating and disallowing SEV/SEV-ES guests without fd-based private
> > memory.
>
> > That would require guest kernel support to communicate private vs. shared,
>
> Could you explain this in more detail? This is required for punching hole for shared pages?
Unlike SEV-SNP, which enumerates private vs. shared in the error code, SEV and SEV-ES
don't provide private vs. shared information to the host (KVM) on page fault. And
it's even more fundamental then that, as SEV/SEV-ES won't even fault if the guest
accesses the "wrong" GPA variant, they'll silent consume/corrupt data.
That means KVM can't support implicit conversions for SEV/SEV-ES, and so an explicit
hypercall is mandatory. SEV doesn't even have a vendor-agnostic guest/host paravirt
ABI, and IIRC SEV-ES doesn't provide a conversion/map hypercall in the GHCB spec, so
running a SEV/SEV-ES guest under UPM would require the guest firmware+kernel to be
properly enlightened beyond what is required architecturally.
next prev parent reply other threads:[~2022-03-30 19:47 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-08 4:38 [PATCH RFC v1 0/9] KVM: SVM: Defer page pinning for SEV guests Nikunj A Dadhania
2022-03-08 4:38 ` [PATCH RFC v1 1/9] KVM: Introduce pinning flag to hva_to_pfn* Nikunj A Dadhania
2022-03-08 4:38 ` [PATCH RFC v1 2/9] KVM: x86/mmu: Move hugepage adjust to direct_page_fault Nikunj A Dadhania
2022-03-28 21:04 ` Sean Christopherson
2022-03-08 4:38 ` [PATCH RFC v1 3/9] KVM: x86/mmu: Add hook to pin PFNs on demand in MMU Nikunj A Dadhania
2022-03-08 4:38 ` [PATCH RFC v1 4/9] KVM: SVM: Add pinning metadata in the arch memslot Nikunj A Dadhania
2022-03-08 4:38 ` [PATCH RFC v1 5/9] KVM: SVM: Implement demand page pinning Nikunj A Dadhania
2022-03-08 21:53 ` Mingwei Zhang
2022-03-09 5:10 ` Nikunj A. Dadhania
2022-03-21 6:11 ` Mingwei Zhang
2022-03-21 9:19 ` Nikunj A. Dadhania
2022-03-08 4:38 ` [PATCH RFC v1 6/9] KVM: x86/mmu: Introduce kvm_mmu_map_tdp_page() for use by SEV/TDX Nikunj A Dadhania
2022-03-08 4:38 ` [PATCH RFC v1 7/9] KVM: SEV: Carve out routine for allocation of pages Nikunj A Dadhania
2022-03-08 4:38 ` [PATCH RFC v1 8/9] KVM: Move kvm_for_each_memslot_in_hva_range() to be used in SVM Nikunj A Dadhania
2022-03-08 4:38 ` [PATCH RFC v1 9/9] KVM: SVM: Pin SEV pages in MMU during sev_launch_update_data() Nikunj A Dadhania
2022-03-09 16:57 ` Maciej S. Szmigiero
2022-03-09 17:47 ` Nikunj A. Dadhania
2022-03-28 21:00 ` [PATCH RFC v1 0/9] KVM: SVM: Defer page pinning for SEV guests Sean Christopherson
2022-03-30 4:42 ` Nikunj A. Dadhania
2022-03-30 19:47 ` Sean Christopherson [this message]
2022-03-31 4:48 ` Nikunj A. Dadhania
2022-03-31 18:32 ` Peter Gonda
2022-03-31 19:00 ` Sean Christopherson
2022-04-01 3:22 ` Nikunj A. Dadhania
2022-04-01 14:54 ` Sean Christopherson
2022-04-01 15:39 ` Nikunj A. Dadhania
2022-04-01 17:28 ` Marc Orr
2022-04-01 18:02 ` Sean Christopherson
2022-04-01 18:19 ` Marc Orr
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