> -----Original Message-----
> From: Alex Williamson <[email protected]>
> Sent: Tuesday, September 22, 2026 7:44 AM
> To: Manish Honap <[email protected]>
> Cc: [email protected]; Ankit Agrawal <[email protected]>; [email protected];
> [email protected]; [email protected]; Srirangan
> Madhavan <[email protected]>; [email protected];
> [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]; [email protected]; Yishai
> Hadas <[email protected]>; Shameer Kolothum Thodi
> <[email protected]>; [email protected]; [email protected];
> [email protected]; [email protected]; [email protected]; Neo Jia
> <[email protected]>; Krishnakant Jaju <[email protected]>; Vikram Sethi
> <[email protected]>; Zhi Wang <[email protected]>; linux-
> [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]; linux-
> [email protected]; [email protected]; [email protected]
> Subject: Re: [PATCH v5 17/27] vfio/cxl: Own the whole component register
> BAR
>
> External email: Use caution opening links or attachments
>
>
> On Thu, 17 Sep 2026 00:05:30 +0530
> <[email protected]> wrote:
>
> > From: Manish Honap <[email protected]>
> >
> > devm_cxl_probe_mem() maps the component registers through the CXL
> > core, which by default claims each HDM and RAS sub-block. That
> > collides with the full-BAR request vfio-pci-core makes when the guest opens
> the device.
> >
> > After the component registers are discovered, declare the containing
> > BAR owned with cxl_reg_map_add_owned_resource(). The core then
> > ioremaps the sub-blocks without requesting them, so vfio-pci-core owns
> > the whole BAR and the requests do not collide.
> >
> > Assisted-by: LLM
> > Signed-off-by: Manish Honap <[email protected]>
> > ---
> > drivers/vfio/pci/cxl/vfio_cxl_core.c | 9 +++++++++
> > 1 file changed, 9 insertions(+)
> >
> > diff --git a/drivers/vfio/pci/cxl/vfio_cxl_core.c
> > b/drivers/vfio/pci/cxl/vfio_cxl_core.c
> > index 0d92e6a409c1..5c8a63833a43 100644
> > --- a/drivers/vfio/pci/cxl/vfio_cxl_core.c
> > +++ b/drivers/vfio/pci/cxl/vfio_cxl_core.c
> > @@ -89,6 +89,15 @@ static int vfio_cxl_init_device(struct
> vfio_pci_core_device *vdev)
> > goto err;
> > }
> >
> > + /*
> > + * vfio-pci-core requests the whole component-register BAR when the
> > + * guest opens the device. Declare that BAR owned so the CXL core
> > + * ioremaps the HDM and RAS sub-blocks without claiming them, and the
> > + * full-BAR request does not collide.
> > + */
> > + cxl_reg_map_add_owned_resource(&cxl->cxlds.reg_map,
> > + pci_resource_n(pdev,
> > + pdev->hdm->hdm_bar));
> > +
>
> The result of this operation is setting a singleton "owned" pointer to this
> resource, whereas the name suggests it's adding the resource to some set of
> owned resources. Is "set" really the more idiomatic verb for this than "add"?
> Thanks,
>
Yes. I will rename it to cxl_reg_map_set_owned_resource() in v6.
> Alex
>
> > if (!cxl->cxlds.reg_map.component_map.hdm_decoder.valid) {
> > pci_err(pdev, "vfio-cxl: HDM decoder registers not found\n");
> > ret = -ENODEV;
