On Wed, Mar 11, 2020 at 01:45:00PM +0100, Jean-Philippe Brucker wrote:
> IOMMU drivers need to perform several tests when checking if a device
> supports ATS. Move them all into a new function that returns true when
> a device and its host bridge support ATS.
>
> Since pci_enable_ats() now calls pci_ats_supported(), the following
> new checks are now common:
> * whether a device is trusted. Devices plugged into external-facing
> ports such as thunderbolt are untrusted.
> * whether the host bridge supports ATS, which defaults to true unless
> the firmware description states that ATS isn't supported by the host
> bridge.
>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> ---
> drivers/pci/ats.c | 30 +++++++++++++++++++++++++++++-
> include/linux/pci-ats.h | 3 +++
> 2 files changed, 32 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
> index 390e92f2d8d1..bbfd0d42b8b9 100644
> --- a/drivers/pci/ats.c
> +++ b/drivers/pci/ats.c
> @@ -30,6 +30,34 @@ void pci_ats_init(struct pci_dev *dev)
> dev->ats_cap = pos;
> }
>
> +/**
> + * pci_ats_supported - check if the device can use ATS
> + * @dev: the PCI device
> + *
> + * Returns true if the device supports ATS and is allowed to use it, false
> + * otherwise.
> + */
> +bool pci_ats_supported(struct pci_dev *dev)
> +{
> + struct pci_host_bridge *bridge;
> +
> + if (!dev->ats_cap)
> + return false;
> +
> + if (dev->untrusted)
> + return false;
> +
> + bridge = pci_find_host_bridge(dev->bus);
> + if (!bridge)
> + return false;
> +
> + if (!bridge->ats_supported)
> + return false;
> +
> + return true;
I assume this is the same as
return bridge->ats_supported;
Only "assuming" because I'm not a C language lawyer, but I assume it
does the obvious conversion from unsigned:1 to bool.
> +}
