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SubjectRe: [PATCH 4/4] vfio-pci/zdev: use a device region to retrieve zPCI information
On Sat, 19 Sep 2020 11:28:38 -0400
Matthew Rosato <mjrosato@linux.ibm.com> wrote:

> Define a new configuration entry VFIO_PCI_ZDEV for VFIO/PCI.
>
> When this s390-only feature is configured we initialize a new device
> region, VFIO_REGION_SUBTYPE_IBM_ZPCI_CLP, to hold information provided
> by the underlying hardware.
>
> This patch is based on work previously done by Pierre Morel.
>
> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> ---
> drivers/vfio/pci/Kconfig | 13 ++
> drivers/vfio/pci/Makefile | 1 +
> drivers/vfio/pci/vfio_pci.c | 8 ++
> drivers/vfio/pci/vfio_pci_private.h | 10 ++
> drivers/vfio/pci/vfio_pci_zdev.c | 242 ++++++++++++++++++++++++++++++++++++

Maybe you want to add yourself to MAINTAINERS for the zdev-specific
files? You're probably better suited to review changes to the
zpci-specific code :)

> 5 files changed, 274 insertions(+)
> create mode 100644 drivers/vfio/pci/vfio_pci_zdev.c

(...)

> +int vfio_pci_zdev_init(struct vfio_pci_device *vdev)
> +{
> + struct vfio_region_zpci_info *region;
> + struct zpci_dev *zdev;
> + size_t clp_offset;
> + int size;
> + int ret;
> +
> + if (!vdev->pdev->bus)
> + return -ENODEV;
> +
> + zdev = to_zpci(vdev->pdev);
> + if (!zdev)
> + return -ENODEV;
> +
> + /* Calculate size needed for all supported CLP features */
> + size = sizeof(*region) +
> + sizeof(struct vfio_region_zpci_info_qpci) +
> + sizeof(struct vfio_region_zpci_info_qpcifg) +
> + (sizeof(struct vfio_region_zpci_info_util) + CLP_UTIL_STR_LEN) +
> + (sizeof(struct vfio_region_zpci_info_pfip) +
> + CLP_PFIP_NR_SEGMENTS);
> +
> + region = kmalloc(size, GFP_KERNEL);
> + if (!region)
> + return -ENOMEM;
> +
> + /* Fill in header */
> + region->argsz = size;
> + clp_offset = region->offset = sizeof(struct vfio_region_zpci_info);
> +
> + /* Fill the supported CLP features */
> + clp_offset = vfio_pci_zdev_add_qpci(zdev, region, clp_offset);
> + clp_offset = vfio_pci_zdev_add_qpcifg(zdev, region, clp_offset);
> + clp_offset = vfio_pci_zdev_add_util(zdev, region, clp_offset);
> + clp_offset = vfio_pci_zdev_add_pfip(zdev, region, clp_offset);

So, the regions are populated once. Can any of the values in the
hardware structures be modified by a guest? Or changed from the
hardware side?

> +
> + ret = vfio_pci_register_dev_region(vdev,
> + PCI_VENDOR_ID_IBM | VFIO_REGION_TYPE_PCI_VENDOR_TYPE,
> + VFIO_REGION_SUBTYPE_IBM_ZPCI_CLP, &vfio_pci_zdev_regops,
> + size, VFIO_REGION_INFO_FLAG_READ, region);
> + if (ret)
> + kfree(region);
> +
> + return ret;
> +}

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