[Qemu-devel] RFC: vfio API changes needed for powerpc (v2)

[Yoder Stuart-B08248]

Based on the email thread over the last couple of days, I have
below an more concrete proposal (v2) for new ioctls supporting vfio-pci
on SoCs with the Freescale PAMU.

Example usage is as described by Scott:

count = VFIO_IOMMU_GET_MSI_BANK_COUNT
VFIO_IOMMU_SET_ATTR(ATTR_GEOMETRY)
VFIO_IOMMU_SET_ATTR(ATTR_WINDOWS)
// do other DMA maps now, or later, or not at all, doesn't matter
for (i = 0; i < count; i++)
        VFIO_IOMMU_MAP_MSI_BANK(iova, i);
// The kernel now knows where each bank has been mapped, and can
//   update PCI config space appropriately.

Thanks,
Stuart

----------------------------------------------------------------------------

The Freescale PAMU is an aperture-based IOMMU with the following 
characteristics.  Each device has an entry in a table in memory
describing the iova->phys mapping. The mapping has:
   -an overall aperture that is power of 2 sized, and has a start iova that
    is naturally aligned
   -has 1 or more windows within the aperture
      -number of windows must be power of 2, max is 256
      -size of each window is determined by aperture size / # of windows
      -iova of each window is determined by aperture start iova / # of windows
      -the mapped region in each window can be different than
       the window size...mapping must power of 2 
      -physical address of the mapping must be naturally aligned
       with the mapping size

/*
 * VFIO_PAMU_GET_ATTR
 *
 * Gets the iommu attributes for the current vfio container.  This 
 * ioctl is applicable to an iommu type of VFIO_PAMU only.
 * Caller sets argsz and attribute.  The ioctl fills in
 * the provided struct vfio_pamu_attr based on the attribute
 * value that was set.
 * Operates on VFIO file descriptor (/dev/vfio/vfio).
 * Return: 0 on success, -errno on failure
 */
struct vfio_pamu_attr {
        __u32   argsz;
        __u32   attribute;
#define VFIO_ATTR_GEOMETRY     1
#define VFIO_ATTR_WINDOWS      2
#define VFIO_ATTR_PAMU_STASH   3

        /* fowlling fields are for VFIO_ATTR_GEOMETRY */
        __u64 aperture_start; /* first address that can be mapped    */
        __u64 aperture_end;   /* last address that can be mapped     */

        /* follwing fields are for VFIO_ATTR_WINDOWS */
        __u32 windows;        /* number of windows in the aperture */
                              /* initially this will be the max number
                               * of windows that can be set
                               */

        /* following fields are for VFIO_ATTR_PAMU_STASH */
        __u32 cpu;            /* CPU number for stashing */
        __u32 cache;          /* cache ID for stashing */
};
#define VFIO_PAMU_GET_ATTR  _IO(VFIO_TYPE, VFIO_BASE + x,
        struct vfio_pamu_attr)

/*
 * VFIO_PAMU_SET_ATTR
 *
 * Sets the iommu attributes for the current vfio container.  This 
 * ioctl is applicable to an iommu type of VFIO_PAMU only.
 * Caller sets struct vfio_pamu attr, including argsz and attribute and
 * setting any fields that are valid for the attribute.
 * Operates on VFIO file descriptor (/dev/vfio/vfio).
 * Return: 0 on success, -errno on failure
 */
#define VFIO_PAMU_SET_ATTR  _IO(VFIO_TYPE, VFIO_BASE + x,
        struct vfio_pamu_attr)

/*
 * VFIO_PAMU_GET_MSI_BANK_COUNT
 *
 * Returns the number of MSI banks for this platform.  This tells user space
 * how many aperture windows should be reserved for MSI banks when setting
 * the PAMU geometry and window count.
 * Fills in provided struct vfio_pamu_msi_banks. Caller sets argsz. 
 * Operates on VFIO file descriptor (/dev/vfio/vfio).
 * Return: 0 on success, -errno on failure
 */
struct vfio_pamu_msi_banks {
        __u32   argsz;
        __u32   bank_count;  /* the number of MSI
};
#define VFIO_PAMU_GET_MSI_BANK_COUNT  _IO(VFIO_TYPE, VFIO_BASE + x,
        struct vfio_pamu_msi_banks)

/*
 * VFIO_PAMU_MAP_MSI_BANK
 *
 * Maps the MSI bank at the specified index and iova.  User space must
 * call this ioctl once for each MSI bank (count of banks is returned by
 * VFIO_IOMMU_GET_MSI_BANK_COUNT).
 * Caller provides struct vfio_pamu_msi_bank_map with all fields set.
 * Operates on VFIO file descriptor (/dev/vfio/vfio).
 * Return: 0 on success, -errno on failure
 */

struct vfio_pamu_msi_bank_map {
        __u32   argsz;
        __u32   msi_bank_index;  /* the index of the MSI bank */
        __u64   iova;      /* the iova the bank is to be mapped to */
};

/*
 * VFIO_PAMU_UNMAP_MSI_BANK
 *
 * Unmaps the MSI bank at the specified iova.
 * Caller provides struct vfio_pamu_msi_bank_unmap with all fields set.
 * Operates on VFIO file descriptor (/dev/vfio/vfio).
 * Return: 0 on success, -errno on failure
 */

struct vfio_pamu_msi_bank_unmap {
        __u32   argsz;
        __u64   iova;      /* the iova to be unmapped to */
};