Re: [PATCH v6 08/11] eal: pci: introduce RTE_KDRV_VFIO_NOIOMMUi driver mode

On Thu, Jan 21, 2016 at 4:02 PM, David Marchand [off-list ref]
wrote:

Santosh,

On Tue, Jan 19, 2016 at 7:57 PM, Santosh Shukla [off-list ref]
wrote:

quoted

Adding RTE_KDRV_VFIO_NOIOMMU mode in kernel driver. Also including
rte_vfio_is_noiommu() helper function. This function will parse
/sys/bus/pci/device/<bus_addr>/ and make sure that
- vfio noiommu mode set in kernel driver
- pci device attached to vfio-noiommu driver only

If both condition satisfies then set drv->kdrv = RTE_KDRV_VFIO_NOIOMMU

Also did similar changes in virtio_rd/wr, Changes applicable for virtio

spec

quoted

0.95 only.

This is a mode (specific to vfio), not a new kernel driver.

Yes, Specific to VFIO and this is why noiommu appended after vfio i.e..
__VFIO and __VFIO_NOIOMMU.

How come we need to distinguish between with/without iommu modes ?

By default vfio framework assumes iommu i.,e., iommu present. Unless user
explicitly set "enable_unsafe_noiommu_mode" param. so in my opinion, we
care to parse vfio driver for _noiommu_ mode only.

Should not vfio behave the same way from an api point of view ?

Yes It should. vfio gives similar file_ops i.e.. read/write/mmap/seek etc..
I am little confused on your question, do you see any issue in vfio bar
rd/wr api implementation?

Regards,
--
David Marchand