From: "Nikunj A. Dadhania" <nikunj@amd.com>
To: Sean Christopherson <seanjc@google.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: Thu, 31 Mar 2022 10:18:33 +0530 [thread overview]
Message-ID: <5567f4ec-bbcf-4caf-16c1-3621b77a1779@amd.com> (raw)
In-Reply-To: <YkSz1R3YuFszcZrY@google.com>
On 3/31/2022 1:17 AM, Sean Christopherson wrote:
> 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.
>
So with guest supporting KVM_FEATURE_HC_MAP_GPA_RANGE and host (KVM) supporting
KVM_HC_MAP_GPA_RANGE hypercall, SEV/SEV-ES guest should communicate private/shared
pages to the hypervisor, this information can be used to mark page shared/private.
Regards,
Nikunj
next prev parent reply other threads:[~2022-03-31 4:49 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
2022-03-31 4:48 ` Nikunj A. Dadhania [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5567f4ec-bbcf-4caf-16c1-3621b77a1779@amd.com \
--to=nikunj@amd.com \
--cc=bharata@amd.com \
--cc=brijesh.singh@amd.com \
--cc=david@redhat.com \
--cc=jmattson@google.com \
--cc=joro@8bytes.org \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mail@maciej.szmigiero.name \
--cc=mizhang@google.com \
--cc=pbonzini@redhat.com \
--cc=pgonda@google.com \
--cc=seanjc@google.com \
--cc=thomas.lendacky@amd.com \
--cc=vkuznets@redhat.com \
--cc=wanpengli@tencent.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).