Re: [dpdk-dev] [PATCH] pci/linux: use RTE_IOVA_VA whenever possible

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

-----Original Message-----
> Date: Thu, 11 Oct 2018 11:26:05 +0100
> From: "Burakov, Anatoly" <anatoly.burakov@intel.com>
> To: Alejandro Lucero <alejandro.lucero@netronome.com>,
>  dariusz.stojaczyk@intel.com
> CC: dev <dev@dpdk.org>, Santosh Shukla <santosh.shukla@caviumnetworks.com>,
>  Hemant Agrawal <hemant.agrawal@nxp.com>, Jerin Jacob
>  <jerin.jacob@caviumnetworks.com>, Maxime Coquelin
>  <maxime.coquelin@redhat.com>, chas3@att.com
> Subject: Re: [dpdk-dev] [PATCH] pci/linux: use RTE_IOVA_VA whenever possible
> User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101
>  Thunderbird/52.9.1
> 
> 
> On 11-Oct-18 11:00 AM, Alejandro Lucero wrote:
> > On Fri, Sep 7, 2018 at 3:55 PM Darek Stojaczyk <dariusz.stojaczyk@intel.com>
> > wrote:
> > 
> > > This allows DPDK to use RTE_IOVA_VA with VFIO/UIO-bound PCI
> > > devices present on the system, but not attached to any
> > > rte_pci_driver at the time of init.
> > > 
> > > So far we used RTE_IOVA_VA whenever there was at least one
> > > device attached to a driver with an RTE_PCI_DRV_IOVA_AS_VA flag,
> > > meaning that other drivers which didn't explicitly report such
> > > flag could have been forced to work in RTE_IOVA_VA as well.
> > > 
> > 
> > This is the opposite. Just one device not being able to use IOVA VA makes
> > all to use IOVA PA.
> > 
> > 
> > > 
> > > This patch makes the RTE_PCI_DRV_IOVA_AS_VA explicitly a hint.
> > > If it's set, but RTE_IOVA_VA cannot be used, then EAL will print
> > > a proper warning.
> > > 
> > > Signed-off-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
> > > ---
> > >   drivers/bus/pci/linux/pci.c | 11 +++++------
> > >   1 file changed, 5 insertions(+), 6 deletions(-)
> > > 
> > > diff --git a/drivers/bus/pci/linux/pci.c b/drivers/bus/pci/linux/pci.c
> > > index 04648ac93..961e24024 100644
> > > --- a/drivers/bus/pci/linux/pci.c
> > > +++ b/drivers/bus/pci/linux/pci.c
> > > @@ -534,7 +534,7 @@ pci_one_device_bound_uio(void)
> > >    * Any one of the device has iova as va
> > >    */
> > >   static inline int
> > > -pci_one_device_has_iova_va(void)
> > > +pci_one_device_want_iova_va(void)
> > >   {
> > >          struct rte_pci_device *dev = NULL;
> > >          struct rte_pci_driver *drv = NULL;
> > > @@ -635,7 +635,7 @@ rte_pci_get_iommu_class(void)
> > >   {
> > >          bool is_bound;
> > >          bool is_vfio_noiommu_enabled = true;
> > > -       bool has_iova_va;
> > > +       bool want_iova_va;
> > >          bool is_bound_uio;
> > >          bool iommu_no_va;
> > > 
> > > @@ -643,7 +643,7 @@ rte_pci_get_iommu_class(void)
> > >          if (!is_bound)
> > >                  return RTE_IOVA_DC;
> > > 
> > > -       has_iova_va = pci_one_device_has_iova_va();
> > > +       want_iova_va = pci_one_device_want_iova_va();
> > >          is_bound_uio = pci_one_device_bound_uio();
> > >          iommu_no_va = !pci_devices_iommu_support_va();
> > >   #ifdef VFIO_PRESENT
> > > @@ -651,11 +651,10 @@ rte_pci_get_iommu_class(void)
> > >                                          true : false;
> > >   #endif
> > > 
> > > -       if (has_iova_va && !is_bound_uio && !is_vfio_noiommu_enabled &&
> > > -                       !iommu_no_va)
> > > +       if (!is_bound_uio && !is_vfio_noiommu_enabled && !iommu_no_va)
> > >                  return RTE_IOVA_VA;
> > > 
> > 
> > This is wrong. A device not able to work with IOVA VA will fail.
> > 
> > 
> > > 
> > > -       if (has_iova_va) {
> > > +       if (want_iova_va) {
> > >                  RTE_LOG(WARNING, EAL, "Some devices want iova as va but pa
> > > will be used because.. ");
> > >                  if (is_vfio_noiommu_enabled)
> > >                          RTE_LOG(WARNING, EAL, "vfio-noiommu mode
> > > configured\n");
> > > --
> > > 2.17.1
> > > 
> > > 
> > 
> 
> For these cases, i think the explicit IOVA mode on command line should
> work better. If the device has not reported IOVA as VA capability, it is
> to be assumed unsupported.

Yes.

> 
> --
> Thanks,
> Anatoly