linux-kernel - Re: [PATCH v1 00/11] KVM: s390: pv: implement lazy destroy

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Date:   Tue, 18 May 2021 18:04:11 +0200
From:   Cornelia Huck <cohuck@...hat.com>
To:     Claudio Imbrenda <imbrenda@...ux.ibm.com>
Cc:     kvm@...r.kernel.org, borntraeger@...ibm.com, frankja@...ux.ibm.com,
        thuth@...hat.com, pasic@...ux.ibm.com, david@...hat.com,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 00/11] KVM: s390: pv: implement lazy destroy

On Tue, 18 May 2021 17:36:24 +0200
Claudio Imbrenda <imbrenda@...ux.ibm.com> wrote:

> On Tue, 18 May 2021 17:05:37 +0200
> Cornelia Huck <cohuck@...hat.com> wrote:
> 
> > On Mon, 17 May 2021 22:07:47 +0200
> > Claudio Imbrenda <imbrenda@...ux.ibm.com> wrote:

> > > This means that the same address space can have memory belonging to
> > > more than one protected guest, although only one will be running,
> > > the others will in fact not even have any CPUs.    
> > 
> > Are those set-aside-but-not-yet-cleaned-up pages still possibly
> > accessible in any way? I would assume that they only belong to the  
> 
> in case of reboot: yes, they are still in the address space of the
> guest, and can be swapped if needed
> 
> > 'zombie' guests, and any new or rebooted guest is a new entity that
> > needs to get new pages?  
> 
> the rebooted guest (normal or secure) will re-use the same pages of the
> old guest (before or after cleanup, which is the reason of patches 3
> and 4)

Took a look at those patches, makes sense.

> 
> the KVM guest is not affected in case of reboot, so the userspace
> address space is not touched.

'guest' is a bit ambiguous here -- do you mean the vm here, and the
actual guest above?