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From: Paolo Bonzini <pbonzini@redhat.com>
To: Steve Rutherford <srutherford@google.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 10:06:47 +0200	[thread overview]
Message-ID: <7c8f388c-1c0e-1fa8-24a5-46ffd40f8b24@redhat.com> (raw)
In-Reply-To: <CABayD+f41GQwCL1818S7iogNHO+MLesLJ-hCX5Bbf_0vFfDMrw@mail.gmail.com>

On 04/05/21 01:22, Steve Rutherford wrote:
> As far as I know, because of MSR filtering, the only "code" that needs
> to be in KVM for MSR handling is a #define reserving the PV feature
> number and a #define for the MSR number.
> 
> Arguably, you don't even need to add the new PV bits to the supported
> cpuid, since MSR filtering is really what determines if kernel support
> is present.

Not only I don't need to do that, I must not. :)

>> At this point I very much prefer the latter, which is basically Ashish's
>> earlier patch.
>
> The minor distinction would be that if you expose the cpuid bit to the
> guest you plan on intercepting the MSR with filters, and would not
> need any handler code in the kernel.

Yep, and it's not a minor distinction after all (especially from the PoV 
of the guy who actually ends up maintaining the code, i.e. me), so 
that's what I'm going for.

Paolo


  reply	other threads:[~2021-05-04  8:06 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 [this message]
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

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