linux-kernel - Re: [PATCH 1/2] KVM: SEV: IBPB-on-Entry guest support

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Message-ID: <f42e878a-d56f-413d-87e1-19acdc6de690@amd.com>
Date: Thu, 29 Jan 2026 16:32:49 -0600
From: Kim Phillips <kim.phillips@....com>
To: Borislav Petkov <bp@...en8.de>
CC: <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>,
	<linux-coco@...ts.linux.dev>, <x86@...nel.org>, Sean Christopherson
	<seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>, K Prateek Nayak
	<kprateek.nayak@....com>, Nikunj A Dadhania <nikunj@....com>, Tom Lendacky
	<thomas.lendacky@....com>, Michael Roth <michael.roth@....com>, Naveen Rao
	<naveen.rao@....com>, David Kaplan <david.kaplan@....com>,
	<stable@...nel.org>
Subject: Re: [PATCH 1/2] KVM: SEV: IBPB-on-Entry guest support

On 1/29/26 4:51 AM, Borislav Petkov wrote:
> On Wed, Jan 28, 2026 at 06:38:29PM -0600, Kim Phillips wrote:
>> SNP_FEATURES_PRESENT is for the non-trivial variety: Its bits get set as
>> part of the patchseries that add the explicit guest support *code*.
> Yes, and I'm asking why can't SNP_FEATURES_PRESENT contain *all* SNP features?

Not *all* SNP features are implemented in all guest kernel versions, and,
well, for those that don't require explicit guest code support, perhaps it's
because they aren't necessarily well defined and validated in all hardware
versions...

Kim