linux-kernel - Re: [PATCH RFC 2/2] KVM: s390: introduce and use KVM_REQ_VSIE

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Date:   Wed, 8 Aug 2018 14:47:33 +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 2/2] KVM: s390: introduce and use
 KVM_REQ_VSIE_RESTART

On Tue,  7 Aug 2018 14:51:31 +0200
David Hildenbrand <david@...hat.com> wrote:

> When we change the crycb (or execution controls), we also have to make sure
> that the vSIE shadow datastructures properly consider the changed
> values before rerunning the vSIE. We can achieve that by simply using a
> VCPU request now.

Is this actually a concrete problem right now, or does this only become
a real concern with vfio-ap?

> 
> This has to be a synchronous request (== handled before entering the
> (v)SIE again).
> 
> The request will make sure that the vSIE handler is left, and that the
> request will be processed (NOP), therefore forcing a reload of all
> vSIE data (including rebuilding the crycb) when re-entering the vSIE
> interception handler the next time.
> 
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>  arch/s390/include/asm/kvm_host.h | 1 +
>  arch/s390/kvm/kvm-s390.c         | 7 ++++++-
>  2 files changed, 7 insertions(+), 1 deletion(-)

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