linux-kernel - Re: [PATCH RFC 1/2] KVM: s390: vsie: simulate VCPU SIE entry/exit

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Date:   Wed, 8 Aug 2018 14:44:14 +0200
From:   Cornelia Huck <cohuck@...hat.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Pierre Morel <pmorel@...ux.ibm.com>
Subject: Re: [PATCH RFC 1/2] KVM: s390: vsie: simulate VCPU SIE entry/exit

On Tue,  7 Aug 2018 14:51:30 +0200
David Hildenbrand <david@...hat.com> wrote:

> VCPU requests and VCPU blocking right now don't take care of the vSIE
> (as it was not necessary until now). But we want to have VCPU requests
> that will also be handled before running the vSIE again.
> 
> So let's simulate a SIE entry when entering the vSIE loop and check
> for PROG_ flags. The existing infrastructure (e.g. exit_sie()) will then
> detect that the SIE (in form of the vSIE execution loop) is running and
> properly kick the vSIE CPU, resulting in it leaving the vSIE loop and
> therefore the vSIE interception handler, allowing it to handle VCPU
> requests.
> 
> E.g. if we want to modify the crycb of the VCPU and make sure that any
> masks also get applied to the VSIE crycb shadow (which uses masks from the
> VCPU crycb), we will need a way to hinder the vSIE from running and make
> sure to process the updated crycb before reentering the vSIE again.
> 
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>  arch/s390/kvm/kvm-s390.c |  9 ++++++++-
>  arch/s390/kvm/kvm-s390.h |  1 +
>  arch/s390/kvm/vsie.c     | 20 ++++++++++++++++++--
>  3 files changed, 27 insertions(+), 3 deletions(-)

Reviewed-by: Cornelia Huck <cohuck@...hat.com>