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

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Message-ID: <24fde6d2-6676-48ca-bc2b-c43b87aa1468@amd.com>
Date: Thu, 21 Aug 2025 10:21:01 -0500
From: "Kalra, Ashish" <ashish.kalra@....com>
To: Sean Christopherson <seanjc@...gle.com>,
 Kim Phillips <kim.phillips@....com>
Cc: 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 8/21/2025 9:16 AM, Sean Christopherson wrote:
> 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).
>

Thanks for that explanation.
 
>> 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.

I have consistently modified all "SEV-ES+SEV-SNP" to "SEV-ES and SEV-SNP" inline/Documentation and commit logs.

I will post a revision fixing the comment above (if it is needed, unless this can be fixed during merge).

Thanks,
Ashish