From: Steve Rutherford <email@example.com> To: Paolo Bonzini <firstname.lastname@example.org> Cc: Sean Christopherson <email@example.com>, LKML <firstname.lastname@example.org>, KVM list <email@example.com>, Joerg Roedel <firstname.lastname@example.org>, Brijesh Singh <email@example.com>, Tom Lendacky <firstname.lastname@example.org>, Ashish Kalra <email@example.com>, Thomas Gleixner <firstname.lastname@example.org>, Ingo Molnar <email@example.com>, "H. Peter Anvin" <firstname.lastname@example.org>, Borislav Petkov <email@example.com>, X86 ML <firstname.lastname@example.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: <email@example.com> On Tue, May 4, 2021 at 1:56 PM Paolo Bonzini <firstname.lastname@example.org> 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]
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