Re: [RFC PATCH V2 10/18] drivers: hv: Decrypt percpu hvcall input arg page in sev-snp enlightened guest

From: Tianyu Lan <ltykernel@gmail.com>
To: Dexuan Cui <decui@microsoft.com>,
	"luto@kernel.org" <luto@kernel.org>,
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	"pbonzini@redhat.com" <pbonzini@redhat.com>,
	"jgross@suse.com" <jgross@suse.com>,
	Tianyu Lan <Tianyu.Lan@microsoft.com>,
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Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
	"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>
Subject: Re: [RFC PATCH V2 10/18] drivers: hv: Decrypt percpu hvcall input arg page in sev-snp enlightened guest
Date: Fri, 9 Dec 2022 10:26:53 +0800	[thread overview]
Message-ID: <5909d07b-4930-6790-e160-ed6c88a8c58a@gmail.com> (raw)
In-Reply-To: <SA1PR21MB13357A3B9348705F4EB59DAFBF1D9@SA1PR21MB1335.namprd21.prod.outlook.com>

On 12/9/2022 5:52 AM, Dexuan Cui wrote:
>> @@ -134,6 +136,16 @@ int hv_common_cpu_init(unsigned int cpu)
>>   	if (!(*inputarg))
>>   		return -ENOMEM;
>>
>> +	if (hv_isolation_type_en_snp()) {
>> +		ret = set_memory_decrypted((unsigned long)*inputarg, 1);
> Is it possible hv_root_partition==1 here? If yes, the pgcount is 2.
>
Hi Dexuan:
	Thanks for review. So far, root partition doesn't support sev 
enlightened guest and so here assume pgcount is always 1. We may use 
pgcount variable here instead of the number.

>> +		if (ret) {
>> +			kfree(*inputarg);
>> +			return ret;
>> +		}
>> +
>> +		memset(*inputarg, 0x00, PAGE_SIZE);
>> +	}
>> +
>>   	if (hv_root_partition) {
>>   		outputarg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
>>   		*outputarg = (char *)(*inputarg) + HV_HYP_PAGE_SIZE;
>> @@ -168,6 +180,9 @@ int hv_common_cpu_die(unsigned int cpu)
>>
>>   	local_irq_restore(flags);
>>
>> +	if (hv_isolation_type_en_snp())
>> +		set_memory_encrypted((unsigned long)mem, 1);
> If set_memory_encrypted() fails, we should not free the 'mem'.

Good point. Will update in the next version.