Re: [RFC PATCH v1 06/10] KVM: s390: Add vm IOCTL for key checked guest absolute memory access

[Thomas Huth]

On 19/01/2022 13.46, Christian Borntraeger wrote:
> Am 19.01.22 um 12:52 schrieb Thomas Huth:
> > On 18/01/2022 10.52, Janis Schoetterl-Glausch wrote:
> > > Channel I/O honors storage keys and is performed on absolute memory.
> > > For I/O emulation user space therefore needs to be able to do key
> > > checked accesses.
> >
> > Can't we do the checking in userspace? We already have functions for 
> > handling the storage keys there (see hw/s390x/s390-skeys-kvm.c), so why 
> > can't we do the checking in QEMU?
>
> That would separate the key check from the memory operation. Potentially for 
> a long time.
> Wenn we piggy back on access_guest_abs_with_key we use mvcos in the host and 
> thus do the key check in lockstep with the keycheck which is the preferrable 
> solution.

Ok, makes sense - Janis, could you please add this rationale to the patch 
description?

 Thomas