Hi Lu,
Tested this on an X1 Carbon G12 with a kernel built form drm-tip and this patch - and was able to boot successfully with pci=noats
Tested-by: Mark Pearson mpearson-lenovo@squebb.ca
Mark
PS - note on small typo below.
On Wed, Sep 4, 2024, at 2:07 AM, Lu Baolu wrote:
SOC-integrated devices on some platforms require their PCI ATS enabled for operation when the IOMMU is in scalable mode. Those devices are reported via ACPI/SATC table with the ATC_REQUIRED bit set in the Flags field.
The PCI subsystem offers the 'pci=noats' kernel command to disable PCI ATS on all devices. Using 'pci=noat' with devices that require PCI ATS
pci=noats
can cause a conflict, leading to boot failure, especially if the device is a graphics device.
To prevent this issue, check PCI ATS support before enumerating the IOMMU devices. If any device requires PCI ATS, but PCI ATS is disabled by 'pci=noats', switch the IOMMU to operate in legacy mode to ensure successful booting.
Fixes: 97f2f2c5317f ("iommu/vt-d: Enable ATS for the devices in SATC table") Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/12036 Cc: stable@vger.kernel.org Signed-off-by: Lu Baolu baolu.lu@linux.intel.com
drivers/iommu/intel/iommu.c | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-)
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c index 4aa070cf56e7..8f275e046e91 100644 --- a/drivers/iommu/intel/iommu.c +++ b/drivers/iommu/intel/iommu.c @@ -3127,10 +3127,26 @@ int dmar_iommu_notify_scope_dev(struct dmar_pci_notify_info *info) (void *)satc + satc->header.length, satc->segment, satcu->devices, satcu->devices_cnt);
if (ret > 0)break;else if (ret < 0)
if (ret < 0) return ret;if (ret > 0) {/** The device requires PCI/ATS when the IOMMU* works in the scalable mode. If PCI/ATS is* disabled using the pci=noats kernel parameter,* the IOMMU will default to legacy mode. Users* are informed of this change.*/if (intel_iommu_sm && satcu->atc_required &&!pci_ats_supported(info->dev)) {pci_warn(info->dev,"PCI/ATS not supported, system working in IOMMU legacy mode\n");intel_iommu_sm = 0;}break;}-- 2.34.1