Messages in this thread Patch in this message | | | Subject | Re: [PATCH 0/2] Introduce PCI_FIXUP_IOMMU | From | Zhangfei Gao <> | Date | Thu, 4 Jun 2020 21:33:07 +0800 |
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On 2020/6/2 上午1:41, Bjorn Helgaas wrote: > On Thu, May 28, 2020 at 09:33:44AM +0200, Joerg Roedel wrote: >> On Wed, May 27, 2020 at 01:18:42PM -0500, Bjorn Helgaas wrote: >>> Is this slowdown significant? We already iterate over every device >>> when applying PCI_FIXUP_FINAL quirks, so if we used the existing >>> PCI_FIXUP_FINAL, we wouldn't be adding a new loop. We would only be >>> adding two more iterations to the loop in pci_do_fixups() that tries >>> to match quirks against the current device. I doubt that would be a >>> measurable slowdown. >> I don't know how significant it is, but I remember people complaining >> about adding new PCI quirks because it takes too long for them to run >> them all. That was in the discussion about the quirk disabling ATS on >> AMD Stoney systems. >> >> So it probably depends on how many PCI devices are in the system whether >> it causes any measureable slowdown. > I found this [1] from Paul Menzel, which was a slowdown caused by > quirk_usb_early_handoff(). I think the real problem is individual > quirks that take a long time. > > The PCI_FIXUP_IOMMU things we're talking about should be fast, and of > course, they're only run for matching devices anyway. So I'd rather > keep them as PCI_FIXUP_FINAL than add a whole new phase. > Thanks Bjorn for taking time for this. If so, it would be much simpler.
+++ b/drivers/iommu/iommu.c @@ -2418,6 +2418,10 @@ int iommu_fwspec_init(struct device *dev, struct fwnode_handle *iommu_fwnode, fwspec->iommu_fwnode = iommu_fwnode; fwspec->ops = ops; dev_iommu_fwspec_set(dev, fwspec); + + if (dev_is_pci(dev)) + pci_fixup_device(pci_fixup_final, to_pci_dev(dev)); +
Then pci_fixup_final will be called twice, the first in pci_bus_add_device. Here in iommu_fwspec_init is the second time, specifically for iommu_fwspec. Will send this when 5.8-rc1 is open.
Thanks
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