[PATCH 6.18 105/314] iommu/vt-d: Skip dev-iotlb flush for inaccessible PCIe device without scalable mode

Sasha Levin
2026-03-10T11:26:20Z

From: Jinhui Guo <guojinhui.liam@bytedance.com>

[ Upstream commit 42662d19839f34735b718129ea200e3734b07e50 ]

PCIe endpoints with ATS enabled and passed through to userspace
(e.g., QEMU, DPDK) can hard-lock the host when their link drops,
either by surprise removal or by a link fault.

Commit 4fc82cd907ac ("iommu/vt-d: Don't issue ATS Invalidation
request when device is disconnected") adds pci_dev_is_disconnected()
to devtlb_invalidation_with_pasid() so ATS invalidation is skipped
only when the device is being safely removed, but it applies only
when Intel IOMMU scalable mode is enabled.

With scalable mode disabled or unsupported, a system hard-lock
occurs when a PCIe endpoint's link drops because the Intel IOMMU
waits indefinitely for an ATS invalidation that cannot complete.

Call Trace:
qi_submit_sync
qi_flush_dev_iotlb
__context_flush_dev_iotlb.part.0
domain_context_clear_one_cb
pci_for_each_dma_alias
device_block_translation
blocking_domain_attach_dev
iommu_deinit_device
__iommu_group_remove_device
iommu_release_device
iommu_bus_notifier
blocking_notifier_call_chain
bus_notify
device_del
pci_remove_bus_device
pci_stop_and_remove_bus_device
pciehp_unconfigure_device
pciehp_disable_slot
pciehp_handle_presence_or_link_change
pciehp_ist

Commit 81e921fd3216 ("iommu/vt-d: Fix NULL domain on device release")
adds intel_pasid_teardown_sm_context() to intel_iommu_release_device(),
which calls qi_flush_dev_iotlb() and can also hard-lock the system
when a PCIe endpoint's link drops.

Call Trace:
qi_submit_sync
qi_flush_dev_iotlb
__context_flush_dev_iotlb.part.0
intel_context_flush_no_pasid
device_pasid_table_teardown
pci_pasid_table_teardown
pci_for_each_dma_alias
intel_pasid_teardown_sm_context
intel_iommu_release_device
iommu_deinit_device
__iommu_group_remove_device
iommu_release_device
iommu_bus_notifier
blocking_notifier_call_chain
bus_notify
device_del
pci_remove_bus_device
pci_stop_and_remove_bus_device
pciehp_unconfigure_device
pciehp_disable_slot
pciehp_handle_presence_or_link_change
pciehp_ist

Sometimes the endpoint loses connection without a link-down event
(e.g., due to a link fault); killing the process (virsh destroy)
then hard-locks the host.

Call Trace:
qi_submit_sync
qi_flush_dev_iotlb
__context_flush_dev_iotlb.part.0
domain_context_clear_one_cb
pci_for_each_dma_alias
device_block_translation
blocking_domain_attach_dev
__iommu_attach_device
__iommu_device_set_domain
__iommu_group_set_domain_internal
iommu_detach_group
vfio_iommu_type1_detach_group
vfio_group_detach_container
vfio_group_fops_release
__fput

pci_dev_is_disconnected() only covers safe-removal paths;
pci_device_is_present() tests accessibility by reading
vendor/device IDs and internally calls pci_dev_is_disconnected().
On a ConnectX-5 (8 GT/s, x2) this costs ~70 µs.

Since __context_flush_dev_iotlb() is only called on
{attach,release}_dev paths (not hot), add pci_device_is_present()
there to skip inaccessible devices and avoid the hard-lock.

Fixes: 37764b952e1b ("iommu/vt-d: Global devTLB flush when present context entry changed")
Fixes: 81e921fd3216 ("iommu/vt-d: Fix NULL domain on device release")
Cc: stable@vger.kernel.org
Signed-off-by: Jinhui Guo <guojinhui.liam@bytedance.com>
Link: https://lore.kernel.org/r/20251211035946.2071-2-guojinhui.liam@bytedance.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/iommu/intel/pasid.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c
index 6782ba5f5e57f..7a64a55fb5887 100644
--- a/drivers/iommu/intel/pasid.c
+++ b/drivers/iommu/intel/pasid.c
@@ -1114,6 +1114,14 @@ static void __context_flush_dev_iotlb(struct device_domain_info *info)
if (!info->ats_enabled)
return;

+ /*
+ * Skip dev-IOTLB flush for inaccessible PCIe devices to prevent the
+ * Intel IOMMU from waiting indefinitely for an ATS invalidation that
+ * cannot complete.
+ */
+ if (!pci_device_is_present(to_pci_dev(info->dev)))
+ return;
+
qi_flush_dev_iotlb(info->iommu, PCI_DEVID(info->bus, info->devfn),
info->pfsid, info->ats_qdep, 0, MAX_AGAW_PFN_WIDTH);

--
2.51.0