linux-kernel - Re: [PATCH v9 2/2] KVM: SEV: Add SEV-SNP CipherTextHiding support

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Message-ID: <aKcpu-EilR04YAxX@google.com>
Date: Thu, 21 Aug 2025 07:16:37 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Kim Phillips <kim.phillips@....com>
Cc: Ashish Kalra <ashish.kalra@....com>, Randy Dunlap <rdunlap@...radead.org>, corbet@....net, 
	pbonzini@...hat.com, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, 
	dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com, 
	thomas.lendacky@....com, herbert@...dor.apana.org, akpm@...ux-foundation.org, 
	rostedt@...dmis.org, paulmck@...nel.org, michael.roth@....com, 
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v9 2/2] KVM: SEV: Add SEV-SNP CipherTextHiding support

On Thu, Aug 21, 2025, Kim Phillips wrote:
> On 8/21/25 5:58 AM, Kalra, Ashish wrote:
> > On 8/21/2025 5:30 AM, Kim Phillips wrote:
> > > On 8/20/25 6:23 PM, Kalra, Ashish wrote:
> > > > On 8/20/2025 5:45 PM, Randy Dunlap wrote:
> > > > > On 8/20/25 1:50 PM, Ashish Kalra wrote:
> > > > > > +        /*
> > > > > > +         * If ciphertext hiding is enabled, the joint SEV-ES/SEV-SNP
> > > > > > +         * ASID range is partitioned into separate SEV-ES and SEV-SNP
> > > > > > +         * ASID ranges, with the SEV-SNP range being [1..max_snp_asid]
> > > > > > +         * and the SEV-ES range being [max_snp_asid..max_sev_es_asid].
> > > > >                                        [max_snp_asid + 1..max_sev_es_asid]
> > > > > ?
> > > > Yes.
> > > So why wouldn't you have left Sean's original "(max_snp_asid..max_sev_es_asid]" as-is?
> > > 
> > > Kim
> > > 
> > Because that i believe is a typo and the correct SEV-ES range is
> > [max_snp_asid + 1..max_sev_es_asid].
> 
> It's not, though.
> 
> [max_snp_asid..max_sev_es_asid]
> 
> and
> 
> (max_snp_asid..max_sev_es_asid]
> 
> are two completely different things.

Yeah, inclusive versus exclusive (I'm quite proud that I remembered which was
which, _and_ that I got it right :-D).

> You also modified Sean's Documentation/ changes.  A consistent "joint
> SEV-ES+SEV-SNP" is preferred.

FWIW, I don't have a strong preference on the exact verbiage, so long as it's
consistent.