1 files changed, 79 insertions, 13 deletions

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 2b53976cd9f9..4caa3388692a 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -2510,6 +2510,48 @@ static void put_hvpcibus(struct hv_pcibus_device *hbus)
 		complete(&hbus->remove_event);
 }
 
+#define HVPCI_DOM_MAP_SIZE (64 * 1024)
+static DECLARE_BITMAP(hvpci_dom_map, HVPCI_DOM_MAP_SIZE);
+
+/*
+ * PCI domain number 0 is used by emulated devices on Gen1 VMs, so define 0
+ * as invalid for passthrough PCI devices of this driver.
+ */
+#define HVPCI_DOM_INVALID 0
+
+/**
+ * hv_get_dom_num() - Get a valid PCI domain number
+ * Check if the PCI domain number is in use, and return another number if
+ * it is in use.
+ *
+ * @dom: Requested domain number
+ *
+ * return: domain number on success, HVPCI_DOM_INVALID on failure
+ */
+static u16 hv_get_dom_num(u16 dom)
+{
+	unsigned int i;
+
+	if (test_and_set_bit(dom, hvpci_dom_map) == 0)
+		return dom;
+
+	for_each_clear_bit(i, hvpci_dom_map, HVPCI_DOM_MAP_SIZE) {
+		if (test_and_set_bit(i, hvpci_dom_map) == 0)
+			return i;
+	}
+
+	return HVPCI_DOM_INVALID;
+}
+
+/**
+ * hv_put_dom_num() - Mark the PCI domain number as free
+ * @dom: Domain number to be freed
+ */
+static void hv_put_dom_num(u16 dom)
+{
+	clear_bit(dom, hvpci_dom_map);
+}
+
 /**
  * hv_pci_probe() - New VMBus channel probe, for a root PCI bus
  * @hdev:	VMBus's tracking struct for this root PCI bus
@@ -2521,6 +2563,7 @@ static int hv_pci_probe(struct hv_device *hdev,
 			const struct hv_vmbus_device_id *dev_id)
 {
 	struct hv_pcibus_device *hbus;
+	u16 dom_req, dom;
 	int ret;
 
 	/*
@@ -2535,19 +2578,34 @@ static int hv_pci_probe(struct hv_device *hdev,
 	hbus->state = hv_pcibus_init;
 
 	/*
-	 * The PCI bus "domain" is what is called "segment" in ACPI and
-	 * other specs.  Pull it from the instance ID, to get something
-	 * unique.  Bytes 8 and 9 are what is used in Windows guests, so
-	 * do the same thing for consistency.  Note that, since this code
-	 * only runs in a Hyper-V VM, Hyper-V can (and does) guarantee
-	 * that (1) the only domain in use for something that looks like
-	 * a physical PCI bus (which is actually emulated by the
-	 * hypervisor) is domain 0 and (2) there will be no overlap
-	 * between domains derived from these instance IDs in the same
-	 * VM.
+	 * The PCI bus "domain" is what is called "segment" in ACPI and other
+	 * specs. Pull it from the instance ID, to get something usually
+	 * unique. In rare cases of collision, we will find out another number
+	 * not in use.
+	 *
+	 * Note that, since this code only runs in a Hyper-V VM, Hyper-V
+	 * together with this guest driver can guarantee that (1) The only
+	 * domain used by Gen1 VMs for something that looks like a physical
+	 * PCI bus (which is actually emulated by the hypervisor) is domain 0.
+	 * (2) There will be no overlap between domains (after fixing possible
+	 * collisions) in the same VM.
 	 */
-	hbus->sysdata.domain = hdev->dev_instance.b[9] |
-			       hdev->dev_instance.b[8] << 8;
+	dom_req = hdev->dev_instance.b[8] << 8 | hdev->dev_instance.b[9];
+	dom = hv_get_dom_num(dom_req);
+
+	if (dom == HVPCI_DOM_INVALID) {
+		dev_err(&hdev->device,
+			"Unable to use dom# 0x%hx or other numbers", dom_req);
+		ret = -EINVAL;
+		goto free_bus;
+	}
+
+	if (dom != dom_req)
+		dev_info(&hdev->device,
+			 "PCI dom# 0x%hx has collision, using 0x%hx",
+			 dom_req, dom);
+
+	hbus->sysdata.domain = dom;
 
 	hbus->hdev = hdev;
 	refcount_set(&hbus->remove_lock, 1);
@@ -2562,7 +2620,7 @@ static int hv_pci_probe(struct hv_device *hdev,
 					   hbus->sysdata.domain);
 	if (!hbus->wq) {
 		ret = -ENOMEM;
-		goto free_bus;
+		goto free_dom;
 	}
 
 	ret = vmbus_open(hdev->channel, pci_ring_size, pci_ring_size, NULL, 0,
@@ -2639,6 +2697,8 @@ close:
 	vmbus_close(hdev->channel);
 destroy_wq:
 	destroy_workqueue(hbus->wq);
+free_dom:
+	hv_put_dom_num(hbus->sysdata.domain);
 free_bus:
 	free_page((unsigned long)hbus);
 	return ret;
@@ -2720,6 +2780,9 @@ static int hv_pci_remove(struct hv_device *hdev)
 	put_hvpcibus(hbus);
 	wait_for_completion(&hbus->remove_event);
 	destroy_workqueue(hbus->wq);
+
+	hv_put_dom_num(hbus->sysdata.domain);
+
 	free_page((unsigned long)hbus);
 	return 0;
 }
@@ -2747,6 +2810,9 @@ static void __exit exit_hv_pci_drv(void)
 
 static int __init init_hv_pci_drv(void)
 {
+	/* Set the invalid domain number's bit, so it will not be used */
+	set_bit(HVPCI_DOM_INVALID, hvpci_dom_map);
+
 	return vmbus_driver_register(&hv_pci_drv);
 }