linux-kernel - Re: [PATCH v3 1/4] drivers/s390/char: Add Ultravisor io device

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Message-ID: <YjMiiom+zRfkhe6F@kroah.com>
Date:   Thu, 17 Mar 2022 12:59:06 +0100
From:   Greg KH <greg@...ah.com>
To:     Steffen Eiden <seiden@...ux.ibm.com>
Cc:     agordeev@...ux.ibm.com, borntraeger@...ux.ibm.com,
        david@...hat.com, frankja@...ux.ibm.com, gor@...ux.ibm.com,
        hca@...ux.ibm.com, imbrenda@...ux.ibm.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-s390@...r.kernel.org, nrb@...ux.ibm.com, shuah@...nel.org
Subject: Re: [PATCH v3 1/4] drivers/s390/char: Add Ultravisor io device

On Thu, Mar 17, 2022 at 12:07:58PM +0100, Steffen Eiden wrote:
> Hi greg,
> 
> On 3/17/22 10:59, Greg KH wrote:
> > On Thu, Mar 17, 2022 at 09:47:06AM +0000, 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>
> > 
> > Do you have a pointer to the userspace code that interacts with this
> > kernel driver?  That would be good to have to verify that the api here
> > is sane.
> > 
> There is a userspace tool currently under development, however, not yet
> ready to be published.

Then really, this driver should not be merged until the user/kernel api
is determined to work properly, right?  Why submit this now if userspace
isn't working?

thanks,

greg k-h