Re: [qemu-s390x] [Qemu-devel] [PATCH v2] s390x/pci: Set the iommu region size mpcifc request

[Halil Pasic]

On Wed, 16 Jan 2019 17:41:30 +0100
Cornelia Huck <address@hidden> wrote:

> On Wed, 16 Jan 2019 16:44:09 +0100
> Pierre Morel <address@hidden> wrote:
> 
> > On 16/01/2019 15:50, Halil Pasic wrote:
> 
> > > @Connie, will you add the Fixes tag? Do we need a cc stable (since
> > > broken since 2016-06-19)?
> > > 
> > > @Pierre: So you say it's a bug.
> > > What can go wrong because of this?
> > > For example if we interpret pal as a size, I guess we could end up with
> > > the memory region not fitting the guest memory,  
> > 
> > The memory region will be too large compared with what the guest required.
> 
> Honestly, this does not look like QEMU stable material to me.
> 

Based on Pierre's offline explanation, from which I understood, the
worst thing that can happen is, that a buggy guest can render it's pci
function unusable, I have to agree: not stable material.

My problem is my non-existent understanding of zPCI. My intuition was
this should be much nastier than that. I would have appreciated a better
explanation on why this is not a problem in practice though -- best as
a part of the commit message.

Regards,
Halil