[PATCH 4/4] PCI: only enable pci realloc when SRIOV bar is not assigned

[Yinghai Lu]

If bios does not assign those BAR or wrong address, then kernel will
try to do pci realloc.

in that case, user still can use pci=realloc=off to override it.

-v2: According to Jesse, adding one CONFIG option for distribution to
     disable it or enable it.

Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
---
 drivers/pci/Kconfig     |   10 ++++++++++
 drivers/pci/setup-bus.c |   28 ++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 0 deletions(-)

diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index 37856f7..771a037 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -31,6 +31,16 @@ config PCI_DEBUG
 
 	  When in doubt, say N.
 
+config PCI_REALLOC_ENABLE_AUTO
+	bool "PCI Realloc Enable Auto"
+	depends on PCI
+	help
+	  Say Y here if you want the PCI core to detect if pci realloc
+	  need to be enabled. You can always use pci=realloc=on or
+	  pci=realloc=off to override it.
+
+	  When in doubt, say N.
+
 config PCI_STUB
 	tristate "PCI Stub driver"
 	depends on PCI
diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index e21e1c2..c9214a1 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -1294,6 +1294,31 @@ static bool __init pci_realloc_enabled(void)
 	return pci_realloc_enable >= user_enabled;
 }
 
+static void __init pci_realloc_detect(void)
+{
+#if defined(CONFIG_PCI_IOV) && defined(CONFIG_PCI_REALLOC_ENABLE_AUTO)
+	struct pci_dev *dev = NULL;
+
+	if (pci_realloc_enable != undefined)
+		return;
+
+	for_each_pci_dev(dev) {
+		int i;
+
+		for (i = PCI_IOV_RESOURCES; i <= PCI_IOV_RESOURCE_END; i++) {
+			struct resource *r = &dev->resource[i];
+
+			/* Not assigned, or rejected by kernel ? */
+			if (r->flags && !r->start) {
+				pci_realloc_enable = auto_enabled;
+
+				return;
+			}
+		}
+	}
+#endif
+}
+
 /*
  * first try will not touch pci bridge res
  * second  and later try will clear small leaf bridge res
@@ -1315,6 +1340,7 @@ pci_assign_unassigned_resources(void)
 	int pci_try_num = 1;
 
 	/* don't realloc if asked to do so */
+	pci_realloc_detect();
 	if (pci_realloc_enabled()) {
 		int max_depth = pci_get_max_depth();
 
@@ -1349,6 +1375,8 @@ again:
 	if (tried_times >= pci_try_num) {
 		if (pci_realloc_enable == undefined)
 			printk(KERN_INFO "Some PCI device resources are unassigned, try booting with pci=realloc\n");
+		else if (pci_realloc_enable == auto_enabled)
+			printk(KERN_INFO "Automatically enabled pci realloc, if you have problem, try booting with pci=realloc=off\n");
 
 		free_list(&fail_head);
 		goto enable_and_dump;
-- 
1.7.7

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