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

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Message-ID: <7eed1970-4e7d-4b3a-a3c1-198b0a6521d5@amd.com>
Date: Wed, 20 Aug 2025 18:23:35 -0500
From: "Kalra, Ashish" <ashish.kalra@....com>
To: 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 8/20/2025 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.

Thanks,
Ashish

> 
>> +		 * Note, SEV-ES may effectively be disabled if all ASIDs from
>> +		 * the joint range are assigned to SEV-SNP.
>> +		 */