linux-kernel - Re: [PATCH RFC 0/2] KVM: s390: vsie: support VCPU requests

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Date:   Tue, 7 Aug 2018 19:15:02 +0200
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     David Hildenbrand <david@...hat.com>, linux-kernel@...r.kernel.org
Cc:     linux-s390@...r.kernel.org,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>
Subject: Re: [PATCH RFC 0/2] KVM: s390: vsie: support VCPU requests

On 07/08/2018 14:51, David Hildenbrand wrote:
> While discussing AP changes, we discovered that we will have to force
> a CPU using the vSIE to regenerate/reload shadow data structures. For now,
> we have no mechanism for that.
>
> E.g. when clearing AP masks later, we could still have a vSIE CPU making
> use of AP adapters as the masks might not be considered yet in the vSIE
> data structures. We need a way to block entering the vSIE and regenerate
> all shadow data structures once done.
>
> Looks like we can achieve that by simply simulating an ordinary SIE
> entry/exit in the VCPU sie control block (while entering the vSIE loop).
>
> This way, we can support blocking and also synchronous CPU requests.
>
> Only compile tested.
>
> David Hildenbrand (2):
>    KVM: s390: vsie: simulate VCPU SIE entry/exit
>    KVM: s390: introduce and use KVM_REQ_VSIE_RESTART
>
>   arch/s390/include/asm/kvm_host.h |  1 +
>   arch/s390/kvm/kvm-s390.c         | 16 ++++++++++++++--
>   arch/s390/kvm/kvm-s390.h         |  1 +
>   arch/s390/kvm/vsie.c             | 20 ++++++++++++++++++--
>   4 files changed, 34 insertions(+), 4 deletions(-)
>
Thanks David for your patches.

Following my tests, they work fine for our AP use case.

Best regards,

Pierre


-- 
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany