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
> 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.derr...@intel.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
> + return NULL;
> segment = pci_domain_nr(pdev->bus);
> } else if (has_acpi_companion(dev))
> dev = &ACPI_COMPANION(dev)->dev;
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