Re: [dpdk-dev] [bug] dpdk-vfio: Invalid region/index assumption

[Santosh Shukla <santosh.shukla@caviumnetworks.com>]

On Thu, Jul 28, 2016 at 03:44:57AM +0530, Alex Williamson wrote:
> Hi,
> 
> I took a quick look at the dpdk vfio code and spotted an invalid
> assumption that should probably be corrected ASAP.  That is:
> 
> lib/librte_eal/linuxapp/eal/eal_vfio.h:
> #define VFIO_GET_REGION_ADDR(x) ((uint64_t) x << 40ULL)
> #define VFIO_GET_REGION_IDX(x) (x >> 40)

Yes. I agree. We need some way to carry essential vfio region info in pci_dev,
needed for pread/pwrite. currently, rte_intr_handle only has vfio_dev_fd but
thats not sufficient information. I stumbled while adding ioport support in vfio
and took a short path to define region_idx thatway. To get-rid of this, Possible
approach could be;
- add essential vfio region specific info (ie.. offset, idx, flag) in
  rte_intr_handle. 
- or pull dev_fd to rte_pci_device{}; and define region specific details.

Thanks.

> Region offset to index is an implementation detail of the kernel, the
> vfio API defines that the offset of a given region (BAR) is found via
> the offset field of struct vfio_region_info returned via the
> VFIO_DEVICE_GET_REGION_INFO ioctl.  You're free to cache the offset
> into any sort of local variable you like, but the kernel may change the
> implementation of region index to offset at any point in time.  This is
> explicitly not part of the ABI.  Is there a place to file a bug, or is
> this sufficient?  Thanks,
> 
> Alex