linux-kernel - [PATCH 1/3] xen/pci: do not register devices outside of PCI segment scope

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Message-ID: <20250110140152.27624-2-roger.pau@citrix.com>
Date: Fri, 10 Jan 2025 15:01:48 +0100
From: Roger Pau Monne <roger.pau@...rix.com>
To: linux-kernel@...r.kernel.org,
	xen-devel@...ts.xenproject.org
Cc: Roger Pau Monne <roger.pau@...rix.com>,
	Juergen Gross <jgross@...e.com>,
	Stefano Stabellini <sstabellini@...nel.org>,
	Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>
Subject: [PATCH 1/3] xen/pci: do not register devices outside of PCI segment scope

The PCI segment value is limited to 16 bits, however there are buses like VMD
that fake being part of the PCI topology by adding segment with a number
outside the scope of the PCI firmware specification range (>= 0x10000). The
MCFG ACPI Table "PCI Segment Group Number" field is defined as having a 16 bit
width.

Attempting to register or manage those devices with Xen would result in errors
at best, or overlaps with existing devices living on the truncated equivalent
segment values.

Skip notifying Xen about those devices.

Signed-off-by: Roger Pau Monné <roger.pau@...rix.com>
---
 drivers/xen/pci.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/xen/pci.c b/drivers/xen/pci.c
index 416f231809cb..08e82fd1263e 100644
--- a/drivers/xen/pci.c
+++ b/drivers/xen/pci.c
@@ -43,6 +43,13 @@ static int xen_add_device(struct device *dev)
 		pci_mcfg_reserved = true;
 	}
 #endif
+
+	if (pci_domain_nr(pci_dev->bus) >> 16) {
+		dev_info(dev,
+			 "not registering with Xen: invalid PCI segment\n");
+		return 0;
+	}
+
 	if (pci_seg_supported) {
 		DEFINE_RAW_FLEX(struct physdev_pci_device_add, add, optarr, 1);
 
@@ -149,6 +156,12 @@ static int xen_remove_device(struct device *dev)
 	int r;
 	struct pci_dev *pci_dev = to_pci_dev(dev);
 
+	if (pci_domain_nr(pci_dev->bus) >> 16) {
+		dev_info(dev,
+			 "not unregistering with Xen: invalid PCI segment\n");
+		return 0;
+	}
+
 	if (pci_seg_supported) {
 		struct physdev_pci_device device = {
 			.seg = pci_domain_nr(pci_dev->bus),
@@ -182,6 +195,12 @@ int xen_reset_device(const struct pci_dev *dev)
 		.flags = PCI_DEVICE_RESET_FLR,
 	};
 
+	if (pci_domain_nr(dev->bus) >> 16) {
+		dev_info(&dev->dev,
+			 "unable to notify Xen of device reset: invalid PCI segment\n");
+		return 0;
+	}
+
 	return HYPERVISOR_physdev_op(PHYSDEVOP_pci_device_reset, &device);
 }
 EXPORT_SYMBOL_GPL(xen_reset_device);
-- 
2.46.0