RE: [PATCH v5 11/27] vfio/pci: Virtualize the CXL DVSEC in vfio_pci_config.c

[Manish Honap]

> -----Original Message-----
> From: Alex Williamson <alex@xxxxxxxxxxx>
> Sent: Tuesday, September 22, 2026 7:45 AM
> To: Manish Honap <mhonap@xxxxxxxxxx>
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> Subject: Re: [PATCH v5 11/27] vfio/pci: Virtualize the CXL DVSEC in
> vfio_pci_config.c
> 
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> 
> On Thu, 17 Sep 2026 00:05:24 +0530
> <mhonap@xxxxxxxxxx> wrote:
> > +/* Virtualize the CXL DVSEC so a guest cannot reprogram the device
> > +through it. */ static int vfio_cxl_dvsec_init(struct
> > +vfio_pci_core_device *vdev) {
> > +     struct pci_dev *pdev = vdev->pdev;
> > +     u32 dword;
> > +     u16 dvsec;
> > +     int len, ret;
> > +
> > +     dvsec = pci_find_dvsec_capability(pdev, PCI_VENDOR_ID_CXL,
> > +                                       PCI_DVSEC_CXL_DEVICE);
> > +     if (!dvsec)
> > +             return 0;
> > +
> > +     ret = pci_read_config_dword(pdev, dvsec + PCI_DVSEC_HEADER1,
> &dword);
> > +     if (ret)
> > +             return pcibios_err_to_errno(ret);
> > +     len = PCI_DVSEC_HEADER1_LEN(dword);
> > +
> > +     /*
> > +      * The virtualization writes fixed DVSEC offsets up to Status2 (the reset
> > +      * doorbell stamps it). A device that reports a shorter DVSEC is not a
> > +      * usable Type-2 function; leave it as plain vfio-pci rather than index the
> > +      * device-length-sized perm allocation past its end.
> > +      */
> > +     if (len < PCI_DVSEC_CXL_STATUS2 + 2)
> > +             return 0;
> > +
> > +     vdev->cxl_perm = kmalloc_obj(struct perm_bits,
> GFP_KERNEL_ACCOUNT);
> > +     if (!vdev->cxl_perm)
> > +             return -ENOMEM;
> > +
> > +     ret = init_cxl_dvsec_perm(vdev->cxl_perm, len);
> > +     if (ret) {
> > +             kfree(vdev->cxl_perm);
> > +             vdev->cxl_perm = NULL;
> > +             return ret;
> > +     }
> > +
> > +     vdev->cxl_dvsec = dvsec;
> > +     vdev->cxl_dvsec_len = len;
> 
> cxl_dvsec_len is never used here or elsewhere in the series.  Thanks,

Yes, I will remove this in v6.

> 
> Alex
> 
> > +
> > +     return 0;
> > +}
> > +