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

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Message-ID: <922eaff1-b2dc-447c-9b9c-ac1281ee000d@amd.com>
Date: Thu, 21 Aug 2025 05:30:45 -0500
From: Kim Phillips <kim.phillips@....com>
To: "Kalra, Ashish" <ashish.kalra@....com>, Randy Dunlap
	<rdunlap@...radead.org>, <corbet@....net>, <seanjc@...gle.com>,
	<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>
CC: <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 8/20/25 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:
>>> @@ -3064,10 +3070,32 @@ void __init sev_hardware_setup(void)
>>>   out:
>>>   	if (sev_enabled) {
>>>   		init_args.probe = true;
>>> +
>>> +		if (sev_is_snp_ciphertext_hiding_supported())
>>> +			init_args.max_snp_asid = min(nr_ciphertext_hiding_asids,
>>> +						     min_sev_asid - 1);
>>> +
>>>   		if (sev_platform_init(&init_args))
>>>   			sev_supported = sev_es_supported = sev_snp_supported = false;
>>>   		else if (sev_snp_supported)
>>>   			sev_snp_supported = is_sev_snp_initialized();
>>> +
>>> +		if (sev_snp_supported)
>>> +			nr_ciphertext_hiding_asids = init_args.max_snp_asid;
>>> +
>>> +		/*
>>> +		 * 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