Re: [PATCH] PCI/ACS: Enforce pci=noats with Transaction Blocking

From: Alex Williamson
Date: Tue Aug 03 2021 - 14:49:40 EST



Bump.

On Fri, 18 Jun 2021 14:55:14 -0600
Alex Williamson <alex.williamson@xxxxxxxxxx> wrote:

> PCIe Address Translation Services (ATS) provides a mechanism for a
> device to provide an on-device caching translation agent (device
> iotlb). We already have a means to disable support for this feature
> via the pci=noats option. For untrusted and externally facing
> devices, we not only disable ATS support for the device, but we use
> Access Control Services (ACS) Transaction Blocking to actively
> prevent devices from sending TLPs with non-default AT field values.
>
> Extend pci=noats to also make use of PCI_ACS_TB so that not only is
> ATS disabled at the device, but blocked at the downstream ports.
> This provides a means to further lock-down ATS for cases such as
> device assignment, where it may not be the hardware configuration of
> the device that makes it untrusted, but the driver running on the
> device.
>
> Cc: Rajat Jain <rajatja@xxxxxxxxxx>
> Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> ---
> drivers/pci/pci.c | 4 ++--
> drivers/pci/quirks.c | 2 +-
> 2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 68f57d86b243..5aa1bb2ddd80 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -915,8 +915,8 @@ static void pci_std_enable_acs(struct pci_dev *dev)
> /* Upstream Forwarding */
> ctrl |= (cap & PCI_ACS_UF);
>
> - /* Enable Translation Blocking for external devices */
> - if (dev->external_facing || dev->untrusted)
> + /* Enable Translation Blocking for external devices and noats */
> + if (pci_ats_disabled() || dev->external_facing || dev->untrusted)
> ctrl |= (cap & PCI_ACS_TB);
>
> pci_write_config_word(dev, pos + PCI_ACS_CTRL, ctrl);
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 6d74386eadc2..d541076c083a 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -5031,7 +5031,7 @@ static int pci_quirk_enable_intel_spt_pch_acs(struct pci_dev *dev)
> ctrl |= (cap & PCI_ACS_CR);
> ctrl |= (cap & PCI_ACS_UF);
>
> - if (dev->external_facing || dev->untrusted)
> + if (pci_ats_disabled() || dev->external_facing || dev->untrusted)
> ctrl |= (cap & PCI_ACS_TB);
>
> pci_write_config_dword(dev, pos + INTEL_SPT_ACS_CTRL, ctrl);
>
>