[dpdk-dev] [PATCH v6 08/11] eal: pci: introduce RTE_KDRV_VFIO_NOIOMMUi driver mode

[Santosh Shukla]

On Thu, Jan 21, 2016 at 4:02 PM, David Marchand <david.marchand at 6wind.com>
wrote:

> Santosh,
>
> On Tue, Jan 19, 2016 at 7:57 PM, Santosh Shukla <sshukla at mvista.com>
> wrote:
> > 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
> > 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
>