[PATCH 18/19] KVM: PPC: Book3S HV: add passthrough support
Paul Mackerras
paulus at ozlabs.org
Wed Jan 30 16:55:46 AEDT 2019
On Tue, Jan 29, 2019 at 06:44:50PM +0100, Cédric Le Goater wrote:
> On 1/29/19 5:12 AM, Paul Mackerras wrote:
> > On Mon, Jan 28, 2019 at 07:26:00PM +0100, Cédric Le Goater wrote:
> >>
> >> Is clearing the PTEs and repopulating the VMA unsafe ?
> >
> > Actually, now that I come to think of it, there could be any number of
> > VMAs (well, up to almost 64k of them), since once you have a file
> > descriptor you can call mmap on it multiple times.
> >
> > The more I think about it, the more I think that getting userspace to
> > manage the mappings with mmap() and munmap() is the right idea if it
> > can be made to work.
>
> We might be able to mmap() and munmap() regions of ESB pages in the RTAS
> call "ibm,change-msi". I think that's the right spot for it.
I was thinking that the ESB pages should be mmapped for device
interrupts at VM startup or when a device is hot-plugged in, and
munmapped when the device is hot-removed. Maybe the mmap could be
done in conjunction with the KVM_IRQFD call?
What is the reasoning behind doing it in the ibm,change-msi call?
Paul.
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