Re: [PATCH v2 10/22] vfio/pci: Skip reset of preserved device after Live Update

Jacob Pan
2026-03-19T16:39:39Z

Hi David,

On Mon, 16 Mar 2026 11:11:20 -0700
David Matlack <dmatlack@google.com> wrote:

> On Fri, Mar 13, 2026 at 8:39 AM Jacob Pan
> <jacob.pan@linux.microsoft.com> wrote:
> > On Thu, 12 Mar 2026 23:39:45 +0000
> > David Matlack <dmatlack@google.com> wrote:
>
> > > +config VFIO_PCI_LIVEUPDATE
> > > + bool "VFIO PCI support for Live Update (EXPERIMENTAL)"
> > > + depends on LIVEUPDATE && VFIO_PCI
> > > + help
> > > + Support for preserving devices bound to vfio-pci across
> > > a Live
> > > + Update. The eventual goal is that preserved devices can
> > > run
> > > + uninterrupted during a Live Update, including DMA to
> > > preserved
> > > + memory buffers and P2P. However there are many steps
> > > still needed to
> > > + achieve this, including:
> > > +
> > > + - Preservation of iommufd files
> > > + - Preservation of IOMMU driver state
> > In the interim, what do you think about moving forward with noiommu
> > mode without preserving IOMMU driver state?
>
> I haven't gotten a chance to look at your noiommu patches yet, but I
> do think noiommu will probably be a good way to develop the VFIO and
> PCI support for Live Update without blocking on IOMMU driver support.
>
> > I’ve tested your
> > vfio_pci_liveupdate_kexec_test with the noiommu cdev, and it works
> > as expected.
>
> Would you be able to send patches to add noiommu support to VFIO
> selftests? That would be very helpful toward allowing us to develop
> and test Live Update support with noiommu.

It is included in the noiommu patchset; the only difference is that the
VFIO cdev name is prefixed with noiommu, which is not strictly required
and is done out of caution.

/dev/vfio/
|-- devices
| `-- noiommu-vfio0