bus/pci: fix VF memory access

bus/pci: fix VF memory access

To fix CVE-2020-12888, the linux vfio-pci module will invalidate mmaps
and block MMIO access on disabled memory, it will send a SIGBUS to the
application:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=abafbc551fdd

When the application opens the vfio PCI device, the vfio-pci module will
enable the bus memory space through PCI read/write access. According to
the PCIe specification, the 'Memory Space Enable' is always zero for VF:

             Table 9-13 Command Register Changes

Bit Location | PF and VF Register Differences | PF         | VF
             | From Base                      | Attributes | Attributes
-------------+--------------------------------+------------+-----------
             | Memory Space Enable - Does not |            |
             | apply to VFs. Must be hardwired|  Base      |  0b
     1       | to 0b for VFs. VF Memory Space |            |
             | is controlled by the VF MSE bit|            |
             | in the VF Control register.    |            |
-------------+--------------------------------+------------+-----------

Afterwards the vfio-pci will initialize its own virtual PCI config space
data ('vconfig') by reading the VF's physical PCI config space, then the
'Memory Space Enable' bit in vconfig will always be 0b value. This will
make the vfio-pci treat the BAR memory space as disabled, and the SIGBUS
will be triggered if access these BARs.

By investigation, the VF PCI device *passthrough* into the Guest OS by
QEMU has the 'Memory Space Enable' with 1b value. That's because every
PCI driver will start to enable the memory space, and this action will
be hooked by vfio-pci virtual PCI read/write to set the 'Memory Space
Enable' in vconfig space to 1b. So VF runs in guest OS has 'Mem+', but
VF runs in host OS has 'Mem-'.

Align with PCI working mode in Guest/QEMU/Host, in DPDK, enable the PCI
bus memory space explicitly to avoid access on disabled memory.

Fixes: 33604c31354a ("vfio: refactor PCI BAR mapping")
Cc: stable@dpdk.org
Signed-off-by: Haiyue Wang <haiyue.wang@intel.com>
Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>
Tested-by: Harman Kalra <hkalra@marvell.com>
Tested-by: David Marchand <david.marchand@redhat.com>
Tested-by: Thierry Martin <thierry.martin.public@gmail.com>