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References: <20190530174819.1160221-1-benjamin.walker@intel.com>
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In-Reply-To: <4fabfd5f-2ba9-ff45-59dd-cfd01b8d49d5@intel.com>
From: David Marchand <david.marchand@redhat.com>
Date: Thu, 4 Jul 2019 11:18:39 +0200
Message-ID: <CAJFAV8yztKRupkkc8QUT5FstkwNuaRL46Lddgr8TjpKgH1hztA@mail.gmail.com>
To: "Burakov, Anatoly" <anatoly.burakov@intel.com>
Cc: dev <dev@dpdk.org>, Ben Walker <benjamin.walker@intel.com>,
Jerin Jacob Kollanukkaran <jerinj@marvell.com>,
Maxime Coquelin <maxime.coquelin@redhat.com>,
Thomas Monjalon <thomas@monjalon.net>
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Subject: Re: [dpdk-dev] [PATCH v2 3/3] bus/pci: only consider usable devices
to select IOVA mode
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On Wed, Jul 3, 2019 at 12:45 PM Burakov, Anatoly <anatoly.burakov@intel.com>
wrote:
> On 14-Jun-19 10:39 AM, David Marchand wrote:
> > From: Ben Walker <benjamin.walker@intel.com>
> >
> > When selecting the preferred IOVA mode of the pci bus, the current
> > heuristic ("are devices bound?", "are devices bound to UIO?", "are pmd
> > drivers supporting IOVA as VA?" etc..) should honor the device
> > white/blacklist so that an unwanted device does not impact the decision.
> >
> > There is no reason to consider a device which has no driver available.
> >
> > This applies to all OS, so implements this in common code then call a
> > OS specific callback.
> >
> > On Linux side:
> > - the VFIO special considerations should be evaluated only if VFIO
> > support is built,
> > - there is no strong requirement on using VA rather than PA if a driver
> > supports VA, so defaulting to DC in such a case.
> >
> > Signed-off-by: Ben Walker <benjamin.walker@intel.com>
> > Signed-off-by: David Marchand <david.marchand@redhat.com>
> > ---
>
> <snip>
>
> > + const struct rte_pci_device *pdev)
> > {
> > - struct rte_pci_device *dev = NULL;
> > - struct rte_pci_driver *drv = NULL;
> > + enum rte_iova_mode iova_mode = RTE_IOVA_DC;
> > + static int iommu_no_va = -1;
> >
> > - FOREACH_DRIVER_ON_PCIBUS(drv) {
> > - FOREACH_DEVICE_ON_PCIBUS(dev) {
> > - if (!rte_pci_match(drv, dev))
> > - continue;
> > - /*
> > - * just one PCI device needs to be checked out
> because
> > - * the IOMMU hardware is the same for all of them.
> > - */
> > - return pci_one_device_iommu_support_va(dev);
> > + switch (pdev->kdrv) {
> > + case RTE_KDRV_VFIO: {
> > +#ifdef VFIO_PRESENT
> > + static int is_vfio_noiommu_enabled = -1;
> > +
> > + if (is_vfio_noiommu_enabled == -1) {
> > + if (rte_vfio_noiommu_is_enabled() == 1)
> > + is_vfio_noiommu_enabled = 1;
> > + else
> > + is_vfio_noiommu_enabled = 0;
> > + }
> > + if ((pdrv->drv_flags & RTE_PCI_DRV_IOVA_AS_VA) == 0) {
> > + iova_mode = RTE_IOVA_PA;
> > + } else if (is_vfio_noiommu_enabled != 0) {
> > + RTE_LOG(DEBUG, EAL, "Forcing to 'PA', vfio-noiommu
> mode configured\n");
> > + iova_mode = RTE_IOVA_PA;
> > }
> > +#endif
> > + break;
>
> I'm not too well-versed in bus code, so please excuse my ignorance of
> this codebase.
>
> It seems that we would be ignoring drv_flags in case VFIO wasn't
> compiled - if the driver has no RTE_PCI_DRV_IOVA_AS_VA flag, i'm pretty
> sure we can set IOVA mode to PA without caring about VFIO at all. I
> think it would be better to have something like this:
>
> if ((pdrv->drv_flags & RTE_PCI_DRV_IOVA_AS_VA) == 0) {
> iova_mode = RTE_IOVA_PA;
> break; // early exit
> }
>
If the device is bound to VFIO, but the dpdk binary has no vfio support, we
don't need to consider this device in the decision.
Did I miss something in what you suggest?
--
David Marchand