RE: [PATCH v5 12/27] vfio/pci: Call the CXL open and close hooks around device use

[Manish Honap]

> -----Original Message-----
> From: Jonathan Cameron <jic23@xxxxxxxxxx>
> Sent: Saturday, September 26, 2026 3:48 AM
> To: Manish Honap <mhonap@xxxxxxxxxx>
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> Subject: Re: [PATCH v5 12/27] vfio/pci: Call the CXL open and close hooks
> around device use
> 
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> 
> On Thu, 17 Sep 2026 00:05:25 +0530
> <mhonap@xxxxxxxxxx> wrote:
> 
> > From: Manish Honap <mhonap@xxxxxxxxxx>
> >
> > Volatile CXL register state must be sampled from live hardware when
> > the guest opens the device, not at bind, because a low-power
> > transition between bind and open can leave the bind-time values stale.
> >
> > Add open and close to the CXL ops and call them from the common enable
> > and close paths. A failed open unwinds the enable in reverse order:
> > unmap the BARs, drop the excluded ranges, then free the virtual config.
> >
> > Factor the BAR unmap out of vfio_pci_core_disable() into a helper so
> > the enable failure path and the disable path share it.
> >
> > Assisted-by: LLM
> > Signed-off-by: Manish Honap <mhonap@xxxxxxxxxx>
> > ---
> >  drivers/vfio/pci/vfio_pci_core.c | 40 +++++++++++++++++++++++++-------
> >  include/linux/vfio_pci_core.h    |  2 ++
> >  2 files changed, 33 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/vfio/pci/vfio_pci_core.c
> > b/drivers/vfio/pci/vfio_pci_core.c
> > index c5b7a59a4548..2f593b2721a1 100644
> > --- a/drivers/vfio/pci/vfio_pci_core.c
> > +++ b/drivers/vfio/pci/vfio_pci_core.c
> > @@ -591,6 +591,21 @@ static const struct dev_pm_ops
> > vfio_pci_core_pm_ops = {
> >
> >  static void vfio_pci_free_excluded_ranges(struct vfio_pci_core_device
> > *vdev);
> >
> > +static void vfio_pci_core_unmap_bars(struct vfio_pci_core_device
> > +*vdev) {
> > +     struct pci_dev *pdev = vdev->pdev;
> > +     int i, bar;
> > +
> > +     for (i = 0; i < PCI_STD_NUM_BARS; i++) {
>         for (int i = 0; i < PCI_STD_NUM_BARS; i++)
>                 int bar = i + PCI_STD_RESOURCES;
> 
> Nice to keep things tightly scoped where we can.

Agreed; I will change this in v6.

> 
> > +             bar = i + PCI_STD_RESOURCES;
> > +             if (IS_ERR_OR_NULL(vdev->barmap[bar]))
> > +                     continue;
> > +             pci_iounmap(pdev, vdev->barmap[bar]);
> > +             pci_release_selected_regions(pdev, 1 << bar);
> > +             vdev->barmap[bar] = NULL;
> > +     }
> > +}
>