On Thu, Jan 21, 2016 at 4:58 PM, Thomas Monjalon
<thomas.monjalon at 6wind.com> wrote:
> 2016-01-21 16:43, Santosh Shukla:
>> David Marchand <david.marchand at 6wind.com> wrote:
>> > 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.
>
> Woaaa! Your logic is really disappointing :)
> Specific to VFIO => append _NOIOMMU
> If it's for VFIO, it should be called VFIO (that's my logic).
>
I am confused by reading your comment. vfio works for default iommu
and now with noiommu. drv->kdrv need to know driver mode for vfio
case. So that user can simply read drv->kdrv value in their driver and
accordingly use vfio rd/wr api for example {pread/pwrite}. This is how
rte_eal_pci_vfio_read/write_bar() api implemented.And Yes it is called VFIO but with with specifics appended in it. >> > 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. > > Why do we care to parse noiommu only? Because pmd drivers example virtio can work with vfio only in _noiommu_ mode. In particular, virtio spec 0.95 / legacy virtio. So at the initialization (example .. virtio-net) of such pmd driver, pmd driver should know that vfio-with-noiommu mode enabled or not? for that pmd driver simply checks drv->kdrv value. Currently virtio-net pmd driver does resource parsing then resource init for interfaces like UIO/ioport, I intend to do same but only parsing, as resource init for vfio case already taken care by pci_xx_vfio_map() api in virtio-net pmd driver (refer Yaun recently virtio 1.0 recently submitted rte_eal_pci_map patch) Also Yuan in one of earlier thread inclined to remove all the resource parsing api from virtio-net pmd driver. Pl. refer this thread [1] [1] http://dpdk.org/dev/patchwork/patch/9862/ > Even if virtio cannot work in an IOMMU case, there is no reason to add > a VFIO_NOIOMMU type here. > >> > 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? > > I think you should just consider the VFIO API and let the noiommu option > as a kernel configuration detail. vfio apis _are_ considered at low level rd/wr implementation, Has nothing to do with iommu/noiommu mode. See pci_vfio_read/write_bar() implementation, they are using pread64/pwrite64() vfio rd/wr api.
