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

David Matlack
2026-03-19T17:24:31Z

On Thu, Mar 19, 2026 at 9:39 AM Jacob Pan <jacob.pan@linux.microsoft.com> wrote:
>
> 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
>
> https://lore.kernel.org/linux-iommu/20260312155637.376854-10-jacob.pan@linux.microsoft.com/

This one flew under my radar. I will take a look and respond there, thanks!