linux-kernel - Re: [PATCH v4 1/2] drivers/s390/char: Add Ultravisor io device

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Date:   Tue, 17 May 2022 14:41:02 +0200
From:   Janosch Frank <frankja@...ux.ibm.com>
To:     Steffen Eiden <seiden@...ux.ibm.com>, Greg KH <greg@...ah.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Shuah Khan <shuah@...nel.org>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Nico Boehr <nrb@...ux.ibm.com>, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v4 1/2] drivers/s390/char: Add Ultravisor io device

On 5/17/22 10:42, Steffen Eiden wrote:
> 
> 
> On 5/17/22 10:38, Janosch Frank wrote:
>> On 5/10/22 16:47, 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 can call the Retrieve Attestation Measurement
>>> Ultravisor Call using IOCTLs on the uvdevice.
>>>
>>> The uvdevice will do some sanity checks first.
>>> Then, copy the request data to kernel space, build the UVCB,
>>> perform the UV call, and copy the result back to userspace.
>>>
>>> Signed-off-by: Steffen Eiden <seiden@...ux.ibm.com>
>>> Reviewed-by: Janosch Frank <frankja@...ux.ibm.com>
>>
>> I'd like to pick this if I'm allowed to fix the two white space problems
>> below.
> I am fine with that.

Thanks, picked

> 
> Thank you.
> 
>>
>>> ---
>>>    MAINTAINERS                           |   2 +
>>>    arch/s390/include/asm/uv.h            |  23 ++-
>>>    arch/s390/include/uapi/asm/uvdevice.h |  51 +++++
>>>    drivers/s390/char/Kconfig             |  10 +
>>>    drivers/s390/char/Makefile            |   1 +
>>>    drivers/s390/char/uvdevice.c          | 264 ++++++++++++++++++++++++++
>>>    6 files changed, 350 insertions(+), 1 deletion(-)
>>>    create mode 100644 arch/s390/include/uapi/asm/uvdevice.h
>>>    create mode 100644 drivers/s390/char/uvdevice.c
>>>
>>
>>> +#endif  /* __S390_ASM_UVDEVICE_H */
>>
>> There are two spaces between the "endif" and the "/"
>>
>>> diff --git a/drivers/s390/char/Kconfig b/drivers/s390/char/Kconfig
>>> index 6cc4b19acf85..e9b9902abbaf 100644
>>> --- a/drivers/s390/char/Kconfig
>>> +++ b/drivers/s390/char/Kconfig
>>> @@ -100,6 +100,16 @@ config SCLP_OFB
>>>          This option enables the Open-for-Business interface to the s390
>>>          Service Element.
>> [...]
>>> + * uvio_attestation() does a  Retrieve Attestation Measurement
>>> Ultravisor Call.
>>
>> Double space
>>
>>> + * It verifies that the given userspace addresses are valid and
>>> request sizes
>>> + * are sane. Every other check is made by the Ultravisor (UV) and
>>> won't result
>>> + * in a negative return value. It copies the input to kernelspace,
>>> builds the
>>> + * request, sends the UV-call, and copies the result to userspace.
>>> + *
>>