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Date: Fri, 11 Aug 2017 12:17:50 -0500 From: Bjorn Helgaas <helgaas@...nel.org> To: Jon Derrick <jonathan.derrick@...el.com> Cc: linux-pci@...r.kernel.org, iommu@...ts.linux-foundation.org, David Woodhouse <dwmw2@...radead.org>, Keith Busch <keith.busch@...el.com>, Scott Bauer <scott.bauer@...el.com>, David Fugate <david.fugate@...el.com>, linux-kernel@...r.kernel.org Subject: Re: [PATCH 3/3] iommu: prevent VMD child devices from being remapping targets On Mon, Aug 07, 2017 at 01:57:13PM -0600, Jon Derrick wrote: > VMD child devices must use the VMD endpoint's ID as the DMA source. > Because of this, there needs to be a way to link the parent VMD > endpoint's DMAR domain to the VMD child devices' DMAR domain such that > attaching and detaching child devices modify the endpoint's DMAR mapping > and prevents early detaching. > > This is outside the scope of VMD, so disable binding child devices to > prevent unforeseen issues. This functionality may be implemented in the > future. > > This patch prevents VMD child devices from returning an IOMMU, which > prevents it from exposing iommu_group sysfs directories and subsequent > binding by userspace-access drivers such as VFIO. > > Signed-off-by: Jon Derrick <jonathan.derrick@...el.com> > --- > drivers/iommu/intel-iommu.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c > index 687f18f..651a6cd 100644 > --- a/drivers/iommu/intel-iommu.c > +++ b/drivers/iommu/intel-iommu.c > @@ -905,6 +905,11 @@ static struct intel_iommu *device_to_iommu(struct device *dev, u8 *bus, u8 *devf > * the PF instead to find the IOMMU. */ > pf_pdev = pci_physfn(pdev); > dev = &pf_pdev->dev; > + > + /* VMD child devices currently cannot be handled individually */ > + if (pci_bus_is_vmd(pdev->bus)) Aah, this is the bigger reason why you want a general "is VMD" thing. But this is still basically x86-specific code (I do see the ia64 in Kconfig, so I guess maybe ia64 as well). But pci_bus_is_vmd() doesn't feel like a generally useful concept. I see why you need things like this quirk, but it's not clear what useful things other code could do with pci_bus_is_vmd() because we don't have a generic concept of how VMD buses are different than other PCI buses. > + return NULL; > + > segment = pci_domain_nr(pdev->bus); > } else if (has_acpi_companion(dev)) > dev = &ACPI_COMPANION(dev)->dev; > -- > 2.9.4 >
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