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To:     Jason Gunthorpe <jgg@nvidia.com>
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Subject: RE: [patch 21/32] NTB/msi: Convert to msi_on_each_desc()
Thread-Topic: [patch 21/32] NTB/msi: Convert to msi_on_each_desc()
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Date:   Thu, 22 Sep 2022 05:11:00 +0000
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> From: Jason Gunthorpe <jgg@nvidia.com>
> Sent: Wednesday, September 21, 2022 8:48 PM
>=20
> On Wed, Sep 21, 2022 at 07:57:00AM +0000, Tian, Kevin wrote:
> > > From: Jason Gunthorpe <jgg@nvidia.com>
> > > Sent: Tuesday, September 20, 2022 10:10 PM
> > >
> > > On Thu, Sep 15, 2022 at 09:24:07AM +0000, Tian, Kevin wrote:
> > >
> > > > After migration the IRTE index could change hence the addr/data pai=
r
> > > > acquired before migration becomes stale and must be fixed.
> > >
> > > The migration has to keep this stuff stable somehow, it seems
> > > infeasible to fix it after the fact.
> > >
> >
> > This is not how live migration typically works, i.e. we don't try to
> > freeze the same host resource cross migration. It's pretty fragile
> > and the chance of failure is high.
>=20
> Thinking of the interrupt routing as a host resource is the problem -
> it is a device resource and just like PASID the ideal design would
> have each RID have its own stable numberspace scoped within it. The
> entire RID and all its stable numberspace would be copied over.
>=20

Unfortunately it is not the case at least on Intel VT-d. The interrupt
remapping table is per VT-d instead of per RID.