linux-kernel - Re: [PATCH v2 1/3] drivers/s390/char: Add Ultravisor io device

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Date:   Wed, 2 Mar 2022 11:46:38 +0100
From:   Steffen Eiden <seiden@...ux.ibm.com>
To:     Janosch Frank <frankja@...ux.ibm.com>, linux-s390@...r.kernel.org
Cc:     Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v2 1/3] drivers/s390/char: Add Ultravisor io device



On 3/2/22 11:34, Janosch Frank wrote:
> On 2/23/22 15:48, Steffen Eiden wrote:
>> This patch adds a new miscdevice to expose some Ultravisor functions
>> to userspace. Userspace can send IOCTLs to the uvdevice that will then
>> emit a corresponding Ultravisor Call and hands the result over to
>> userspace. The uvdevice is available if the Ultravisor Call facility is
>> present.
>>
>> Userspace is now able to call the Query Ultravisor Information
>> Ultravisor Command through the uvdevice.
>>
>> Signed-off-by: Steffen Eiden <seiden@...ux.ibm.com>
>> ---
[...]
>> +
>> +config S390_UV_UAPI
>> +    def_tristate y
>> +    prompt "Ultravisor userspace API"
>> +    depends on PROTECTED_VIRTUALIZATION_GUEST
> 
> Please drop the dependency.
> We want this to be available to both guest and host as QUI is available 
> in both environments and more calls like this could follow.
> 
> We could put an option around the attestation but the savings are not 
> worth the effort.

Makes sense. I will drop the dependency in v3.

Steffen