linux-kernel - [PATCH v2 2/2] PCI: Add PCI_BRIDGE_NO

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251217154529.377586-2-nirmoyd@nvidia.com>
Date: Wed, 17 Dec 2025 07:45:29 -0800
From: Nirmoy Das <nirmoyd@...dia.com>
To: Bjorn Helgaas <bhelgaas@...gle.com>
CC: <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Robin Murphy
	<robin.murphy@....com>, Jason Gunthorpe <jgg@...dia.com>, Will Deacon
	<will@...nel.org>, Joerg Roedel <joro@...tes.org>, <iommu@...ts.linux.dev>,
	<jammy_huang@...eedtech.com>, <mochs@...dia.com>, Nirmoy Das
	<nirmoyd@...dia.com>
Subject: [PATCH v2 2/2] PCI: Add PCI_BRIDGE_NO_ALIASES quirk for ASPEED AST1150

ASPEED BMC controllers have VGA and USB functions behind a PCIe-to-PCI
bridge that causes them to share the same stream ID:

  [e0]---00.0-[e1-e2]----00.0-[e2]--+-00.0  ASPEED Graphics Family
                                    \-02.0  ASPEED USB Controller

Both devices get stream ID 0x5e200 due to bridge aliasing, causing the
USB controller to be rejected with 'Aliasing StreamID unsupported'.

Per ASPEED, the AST1150 doesn't use a real PCI bus and always forwards
the original requester ID from downstream devices rather than replacing
it with any alias.

Add a new PCI_DEV_FLAGS_PCI_BRIDGE_NO_ALIASES flag and apply it to the
AST1150.

Suggested-by: Jason Gunthorpe <jgg@...dia.com>
Signed-off-by: Nirmoy Das <nirmoyd@...dia.com>
---
v2:
  - Use new PCI_DEV_FLAGS_PCI_BRIDGE_NO_ALIASES flag instead of
    PCI_DEV_FLAGS_BRIDGE_XLATE_ROOT to only skip aliasing at this
    bridge, not stop the entire upstream alias walk (Jason Gunthorpe)

 drivers/pci/quirks.c | 10 ++++++++++
 drivers/pci/search.c |  2 ++
 include/linux/pci.h  |  5 +++++
 3 files changed, 17 insertions(+)

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index b9c252aa6fe0..a37b7305ae5f 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -4453,6 +4453,16 @@ DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_BROADCOM, 0x9000,
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_BROADCOM, 0x9084,
 				quirk_bridge_cavm_thrx2_pcie_root);
 
+/*
+ * AST1150 doesn't use a real PCI bus and always forwards the requester ID
+ * from downstream devices.
+ */
+static void quirk_aspeed_pci_bridge_no_aliases(struct pci_dev *pdev)
+{
+	pdev->dev_flags |= PCI_DEV_FLAGS_PCI_BRIDGE_NO_ALIASES;
+}
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ASPEED, 0x1150, quirk_aspeed_pci_bridge_no_aliases);
+
 /*
  * Intersil/Techwell TW686[4589]-based video capture cards have an empty (zero)
  * class code.  Fix it.
diff --git a/drivers/pci/search.c b/drivers/pci/search.c
index 53840634fbfc..2f44444ae22f 100644
--- a/drivers/pci/search.c
+++ b/drivers/pci/search.c
@@ -86,6 +86,8 @@ int pci_for_each_dma_alias(struct pci_dev *pdev,
 			case PCI_EXP_TYPE_DOWNSTREAM:
 				continue;
 			case PCI_EXP_TYPE_PCI_BRIDGE:
+				if (tmp->dev_flags & PCI_DEV_FLAGS_PCI_BRIDGE_NO_ALIASES)
+					continue;
 				ret = fn(tmp,
 					 PCI_DEVID(tmp->subordinate->number,
 						   PCI_DEVFN(0, 0)), data);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index b16127c6a7b4..963da06ef193 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -248,6 +248,11 @@ enum pci_dev_flags {
 	PCI_DEV_FLAGS_HAS_MSI_MASKING = (__force pci_dev_flags_t) (1 << 12),
 	/* Device requires write to PCI_MSIX_ENTRY_DATA before any MSIX reads */
 	PCI_DEV_FLAGS_MSIX_TOUCH_ENTRY_DATA_FIRST = (__force pci_dev_flags_t) (1 << 13),
+	/*
+	 * PCIe to PCI bridge does not create RID aliases because the bridge is
+	 * integrated with the downstream devices and doesn't use real PCI.
+	 */
+	PCI_DEV_FLAGS_PCI_BRIDGE_NO_ALIASES = (__force pci_dev_flags_t) (1 << 14),
 };
 
 enum pci_irq_reroute_variant {
-- 
2.43.0