From: Steve Rutherford <srutherford@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>,
LKML <linux-kernel@vger.kernel.org>,
KVM list <kvm@vger.kernel.org>, Joerg Roedel <joro@8bytes.org>,
Brijesh Singh <brijesh.singh@amd.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
Ashish Kalra <ashish.kalra@amd.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Borislav Petkov <bp@suse.de>, X86 ML <x86@kernel.org>
Subject: Re: [PATCH v3 2/2] KVM: X86: Introduce KVM_HC_PAGE_ENC_STATUS hypercall
Date: Tue, 4 May 2021 14:16:20 -0700 [thread overview]
Message-ID: <CABayD+eAJjVjoh9GAnvC9z64pL9GnpHomCqXtw_=EPDr=vz7hA@mail.gmail.com> (raw)
In-Reply-To: <55db8e64-763b-9ecc-9c9a-6d840628e763@redhat.com>
On Tue, May 4, 2021 at 1:56 PM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 04/05/21 22:33, Sean Christopherson wrote:
> > On Tue, May 04, 2021, Paolo Bonzini wrote:
> >> On 04/05/21 19:09, Sean Christopherson wrote:
> >>> On Sat, May 01, 2021, Paolo Bonzini wrote:
> >>>> - make it completely independent from migration, i.e. it's just a facet of
> >>>> MSR_KVM_PAGE_ENC_STATUS saying whether the bitmap is up-to-date. It would
> >>>> use CPUID bit as the encryption status bitmap and have no code at all in KVM
> >>>> (userspace needs to set up the filter and implement everything).
> >>>
> >>> If the bit is purely a "page encryption status is up-to-date", what about
> >>> overloading KVM_HC_PAGE_ENC_STATUS to handle that status update as well? That
> >>> would eliminate my biggest complaint about having what is effectively a single
> >>> paravirt feature split into two separate, but intertwined chunks of ABI.
> >>
> >> It's true that they are intertwined, but I dislike not having a way to read
> >> the current state.
> >
> > From the guest?
>
> Yes, host userspace obviously doesn't need one since it's implemented
> through an MSR filter. It may not be really necessary to read it, but
> it's a bit jarring compared to how the rest of the PV APIs uses MSRs.
>
> Also from a debugging/crashdump point of view the VMM may have an
> established way to read an MSR from a vCPU, but it won't work if you
> come up with a new way to set the state.
Agreed on the preference for an MSR. I particularly appreciate that it
reduces the kernel footprint for these changes.
Steve
prev parent reply other threads:[~2021-05-04 21:16 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-29 10:47 [PATCH v3 0/2] KVM: x86: guest interface for SEV live migration Paolo Bonzini
2021-04-29 10:47 ` [PATCH v3 1/2] KVM: x86: add MSR_KVM_MIGRATION_CONTROL Paolo Bonzini
2021-04-29 10:47 ` [PATCH v3 2/2] KVM: X86: Introduce KVM_HC_PAGE_ENC_STATUS hypercall Paolo Bonzini
2021-04-30 20:10 ` Sean Christopherson
2021-05-01 9:01 ` Paolo Bonzini
2021-05-03 23:22 ` Steve Rutherford
2021-05-04 8:06 ` Paolo Bonzini
2021-05-04 17:09 ` Sean Christopherson
2021-05-04 20:27 ` Paolo Bonzini
2021-05-04 20:33 ` Sean Christopherson
2021-05-04 20:56 ` Paolo Bonzini
2021-05-04 21:16 ` Steve Rutherford [this message]
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='CABayD+eAJjVjoh9GAnvC9z64pL9GnpHomCqXtw_=EPDr=vz7hA@mail.gmail.com' \
--to=srutherford@google.com \
--cc=ashish.kalra@amd.com \
--cc=bp@suse.de \
--cc=brijesh.singh@amd.com \
--cc=hpa@zytor.com \
--cc=joro@8bytes.org \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=pbonzini@redhat.com \
--cc=seanjc@google.com \
--cc=tglx@linutronix.de \
--cc=thomas.lendacky@amd.com \
--cc=x86@kernel.org \
/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).