Re: [PATCH v2 1/1] virtio-ccw: auto-manage VIRTIO_F_IOMMU_PLATFORM if PV

[Halil Pasic]

On Wed, 10 Jun 2020 14:25:54 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:

> > > I'm going to definitely have a good look at that. What I think special
> > > about s390 is that F_ACCESS_PLATFORM is hurting us because all IO needs
> > > to go through ZONE_DMA (this is a problem of the implementation that
> > > stemming form a limitation of the DMA API, upstream didn't let me
> > > fix it).   
> > 
> > My understanding is that power runs into similar issues, but I don't
> > know much about power, so I might be entirely wrong :)  
> 
> Sort of, but not to the same extent, I think.

I'm curious what are the ramifications of a misguided hotplug on POWER?
Does using F_ACCESS_PLATFORM when it isn't required have any
significant drawbacks, or are you fine to just go with the safe option?

Regards,
Halil

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