linux-kernel - [PATCH] xen: xen-pciback: Export a bridge and all its children as per TODO

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Message-Id: <20240609184410.53500-1-jain.abhinav177@gmail.com>
Date: Sun,  9 Jun 2024 18:44:10 +0000
From: Abhinav Jain <jain.abhinav177@...il.com>
To: jgross@...e.com,
	sstabellini@...nel.org,
	oleksandr_tyshchenko@...m.com,
	xen-devel@...ts.xenproject.org,
	linux-kernel@...r.kernel.org
Cc: skhan@...uxfoundation.org,
	javier.carrasco.cruz@...il.com,
	jain.abhinav177@...il.com
Subject: [PATCH] xen: xen-pciback: Export a bridge and all its children as per TODO

Check if the device is a bridge.
If it is a bridge, iterate over all its child devices and export them.
Log error if the export fails for any particular device logging details.
Export error string is split across lines as I could see several
other such occurrences in the file.
Please let me know if I should change it in some way.

Signed-off-by: Abhinav Jain <jain.abhinav177@...il.com>
---
 drivers/xen/xen-pciback/xenbus.c | 39 +++++++++++++++++++++++++-------
 1 file changed, 31 insertions(+), 8 deletions(-)

diff --git a/drivers/xen/xen-pciback/xenbus.c b/drivers/xen/xen-pciback/xenbus.c
index b11e401f1b1e..d15271d33ad6 100644
--- a/drivers/xen/xen-pciback/xenbus.c
+++ b/drivers/xen/xen-pciback/xenbus.c
@@ -258,14 +258,37 @@ static int xen_pcibk_export_device(struct xen_pcibk_device *pdev,
 		xen_register_device_domain_owner(dev, pdev->xdev->otherend_id);
 	}
 
-	/* TODO: It'd be nice to export a bridge and have all of its children
-	 * get exported with it. This may be best done in xend (which will
-	 * have to calculate resource usage anyway) but we probably want to
-	 * put something in here to ensure that if a bridge gets given to a
-	 * driver domain, that all devices under that bridge are not given
-	 * to other driver domains (as he who controls the bridge can disable
-	 * it and stop the other devices from working).
-	 */
+	/* Check if the device is a bridge and export all its children */
+	if ((dev->hdr_type && PCI_HEADER_TYPE_MASK) == PCI_HEADER_TYPE_BRIDGE) {
+		struct pci_dev *child = NULL;
+
+		/* Iterate over all the devices in this bridge */
+		list_for_each_entry(child, &dev->subordinate->devices,
+				bus_list) {
+			dev_dbg(&pdev->xdev->dev,
+				"exporting child device %04x:%02x:%02x.%d\n",
+				child->domain, child->bus->number,
+				PCI_SLOT(child->devfn),
+				PCI_FUNC(child->devfn));
+
+			err = xen_pcibk_export_device(pdev,
+						      child->domain,
+						      child->bus->number,
+						      PCI_SLOT(child->devfn),
+						      PCI_FUNC(child->devfn),
+						      devid);
+			if (err) {
+				dev_err(&pdev->xdev->dev,
+					"failed to export child device : "
+					"%04x:%02x:%02x.%d\n",
+					child->domain,
+					child->bus->number,
+					PCI_SLOT(child->devfn),
+					PCI_FUNC(child->devfn));
+				goto out;
+			}
+		}
+	}
 out:
 	return err;
 }
-- 
2.34.1