[PATCH v2 14/31] PCI/TSM: Report active IDE streams per host bridge

[Xu Yilun]

From: Dan Williams <dan.j.williams@xxxxxxxxx>

The first attempt at an ABI for this failed to account for naming
collisions across host bridges:

Commit a4438f06b1db ("PCI/TSM: Report active IDE streams")

Revive this ABI with a per host bridge link that appears at first stream
creation for a given host bridge and disappears after the last stream is
removed.

For systems with many host bridge objects it allows:

    ls /sys/class/tsm/tsmN/pci*/stream*

...to find all the host bridges with active streams without first iterating
over all host bridges. Yilun notes that is handy to have this short cut [1]
and from an administrator perspective it helps with inventory for
constrained stream resources.

Link: http://lore.kernel.org/aXLtILY85oMU5qlb@yilunxu-OptiPlex-7050 [1]
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
 Documentation/ABI/testing/sysfs-class-tsm | 13 +++
 include/linux/pci-ide.h                   |  2 +
 include/linux/tsm.h                       |  3 +
 drivers/pci/ide.c                         |  4 +
 drivers/virt/coco/tsm-core.c              | 97 +++++++++++++++++++++++
 5 files changed, 119 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-class-tsm b/Documentation/ABI/testing/sysfs-class-tsm
index 2949468deaf7..1ddb8f357961 100644
--- a/Documentation/ABI/testing/sysfs-class-tsm
+++ b/Documentation/ABI/testing/sysfs-class-tsm
@@ -7,3 +7,16 @@ Description:
 		signals when the PCI layer is able to support establishment of
 		link encryption and other device-security features coordinated
 		through a platform tsm.
+
+What:		/sys/class/tsm/tsmN/pciDDDD:BB
+Contact:	linux-pci@xxxxxxxxxxxxxxx
+Description:
+		(RO) When a PCIe host bridge has established a secure connection
+		via a TSM to an endpoint, this symlink appears. It facilitates a
+		TSM instance scoped view of PCIe Link Encryption and Secure
+		Session resource consumption across host bridges. The symlink
+		appears when a host bridge has 1 or more IDE streams established
+		with this TSM, and disappears when that number returns to 0. See
+		Documentation/ABI/testing/sysfs-devices-pci-host-bridge for the
+		description of the pciDDDD:BB/streamH.R.E symlink and the
+		pciDDDD:BB/available_secure_streams attribute.
diff --git a/include/linux/pci-ide.h b/include/linux/pci-ide.h
index ae07d9f699c0..381a1bf22a95 100644
--- a/include/linux/pci-ide.h
+++ b/include/linux/pci-ide.h
@@ -82,6 +82,7 @@ struct pci_ide_regs {
  * @host_bridge_stream: allocated from host bridge @ide_stream_ida pool
  * @stream_id: unique Stream ID (within Partner Port pairing)
  * @name: name of the established Selective IDE Stream in sysfs
+ * @tsm_dev: For TSM established IDE, the TSM device context
  *
  * Negative @stream_id values indicate "uninitialized" on the
  * expectation that with TSM established IDE the TSM owns the stream_id
@@ -93,6 +94,7 @@ struct pci_ide {
 	u8 host_bridge_stream;
 	int stream_id;
 	const char *name;
+	struct tsm_dev *tsm_dev;
 };
 
 /*
diff --git a/include/linux/tsm.h b/include/linux/tsm.h
index 381c53244c83..7f72a154b6b2 100644
--- a/include/linux/tsm.h
+++ b/include/linux/tsm.h
@@ -123,4 +123,7 @@ int tsm_report_unregister(const struct tsm_report_ops *ops);
 struct tsm_dev *tsm_register(struct device *parent, struct pci_tsm_ops *ops);
 void tsm_unregister(struct tsm_dev *tsm_dev);
 struct tsm_dev *find_tsm_dev(int id);
+struct pci_ide;
+int tsm_ide_stream_register(struct pci_ide *ide);
+void tsm_ide_stream_unregister(struct pci_ide *ide);
 #endif /* __TSM_H */
diff --git a/drivers/pci/ide.c b/drivers/pci/ide.c
index be74e8f0ae21..b35e8aba7ecb 100644
--- a/drivers/pci/ide.c
+++ b/drivers/pci/ide.c
@@ -11,6 +11,7 @@
 #include <linux/pci_regs.h>
 #include <linux/slab.h>
 #include <linux/sysfs.h>
+#include <linux/tsm.h>
 
 #include "pci.h"
 
@@ -372,6 +373,9 @@ void pci_ide_stream_release(struct pci_ide *ide)
 	if (ide->partner[PCI_IDE_EP].enable)
 		pci_ide_stream_disable(pdev, ide);
 
+	if (ide->tsm_dev)
+		tsm_ide_stream_unregister(ide);
+
 	if (ide->partner[PCI_IDE_RP].setup)
 		pci_ide_stream_teardown(rp, ide);
 
diff --git a/drivers/virt/coco/tsm-core.c b/drivers/virt/coco/tsm-core.c
index 98dcf7d836df..ece7cd7ea9d8 100644
--- a/drivers/virt/coco/tsm-core.c
+++ b/drivers/virt/coco/tsm-core.c
@@ -4,10 +4,12 @@
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
 #include <linux/tsm.h>
+#include <linux/pci.h>
 #include <linux/device.h>
 #include <linux/module.h>
 #include <linux/cleanup.h>
 #include <linux/pci-tsm.h>
+#include <linux/pci-ide.h>
 
 static struct class *tsm_class;
 static DEFINE_IDA(tsm_ida);
@@ -104,6 +106,100 @@ void tsm_unregister(struct tsm_dev *tsm_dev)
 }
 EXPORT_SYMBOL_GPL(tsm_unregister);
 
+static DEFINE_XARRAY(tsm_ide_streams);
+static DEFINE_MUTEX(tsm_ide_streams_lock);
+
+/* tracker for the bridge symlink when the bridge has any streams */
+struct tsm_ide_stream {
+	struct tsm_dev *tsm_dev;
+	struct pci_host_bridge *bridge;
+	struct kref kref;
+};
+
+static struct tsm_ide_stream *create_streams(struct tsm_dev *tsm_dev,
+					    struct pci_host_bridge *bridge)
+{
+	int rc;
+
+	struct tsm_ide_stream *streams __free(kfree) =
+		kzalloc(sizeof(*streams), GFP_KERNEL);
+	if (!streams)
+		return NULL;
+
+	streams->tsm_dev = tsm_dev;
+	streams->bridge = bridge;
+	kref_init(&streams->kref);
+	rc = xa_insert(&tsm_ide_streams, (unsigned long)bridge, streams,
+		       GFP_KERNEL);
+	if (rc)
+		return NULL;
+
+	rc = sysfs_create_link(&tsm_dev->dev.kobj, &bridge->dev.kobj,
+			       dev_name(&bridge->dev));
+	if (rc) {
+		xa_erase(&tsm_ide_streams, (unsigned long)bridge);
+		return NULL;
+	}
+
+	return no_free_ptr(streams);
+}
+
+int tsm_ide_stream_register(struct pci_ide *ide)
+{
+	struct tsm_ide_stream *streams;
+	struct pci_dev *pdev = ide->pdev;
+	struct pci_tsm *tsm = pdev->tsm;
+	struct tsm_dev *tsm_dev = tsm->tsm_dev;
+	struct pci_host_bridge *bridge = pci_find_host_bridge(pdev->bus);
+
+	guard(mutex)(&tsm_ide_streams_lock);
+	streams = xa_load(&tsm_ide_streams, (unsigned long)bridge);
+	if (streams)
+		kref_get(&streams->kref);
+	else
+		streams = create_streams(tsm_dev, bridge);
+
+	if (!streams)
+		return -ENOMEM;
+	ide->tsm_dev = tsm_dev;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tsm_ide_stream_register);
+
+static void destroy_streams(struct kref *kref)
+{
+	struct tsm_ide_stream *streams =
+		container_of(kref, struct tsm_ide_stream, kref);
+	struct tsm_dev *tsm_dev = streams->tsm_dev;
+	struct pci_host_bridge *bridge = streams->bridge;
+
+	lockdep_assert_held(&tsm_ide_streams_lock);
+	sysfs_remove_link(&tsm_dev->dev.kobj, dev_name(&bridge->dev));
+	xa_erase(&tsm_ide_streams, (unsigned long)bridge);
+	kfree(streams);
+}
+
+void tsm_ide_stream_unregister(struct pci_ide *ide)
+{
+	struct tsm_ide_stream *streams;
+	struct tsm_dev *tsm_dev = ide->tsm_dev;
+	struct pci_dev *pdev = ide->pdev;
+	struct pci_host_bridge *bridge = pci_find_host_bridge(pdev->bus);
+
+	guard(mutex)(&tsm_ide_streams_lock);
+	streams = xa_load(&tsm_ide_streams, (unsigned long)bridge);
+	/* catch API abuse */
+	if (dev_WARN_ONCE(&tsm_dev->dev,
+			  !streams || streams->tsm_dev != tsm_dev,
+			  "no IDE streams associated with %s\n",
+			  dev_name(&bridge->dev)))
+		return;
+	kref_put(&streams->kref, destroy_streams);
+	ide->tsm_dev = NULL;
+}
+EXPORT_SYMBOL_GPL(tsm_ide_stream_unregister);
+
 static void tsm_release(struct device *dev)
 {
 	struct tsm_dev *tsm_dev = container_of(dev, typeof(*tsm_dev), dev);
@@ -126,6 +222,7 @@ module_init(tsm_init)
 static void __exit tsm_exit(void)
 {
 	class_destroy(tsm_class);
+	xa_destroy(&tsm_ide_streams);
 }
 module_exit(tsm_exit)
 
-- 
2.25.1