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

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Message-ID: <bae6b9f0-dd4d-f109-b220-f6b118c889ad@linux.ibm.com>
Date:   Tue, 17 May 2022 10:38:38 +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 5/10/22 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.

> ---
>   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.
> + *