PCI: add a PCI resource reallocation config option

Add a new config option, PCI_REALLOC_ENABLE_AUTO, which will
automatically try to re-allocate PCI resources if PCI_IOV support is
enabled and the SR-IOV resources are unassigned.  Behavior can still be
controlled using the pci=realloc= parameter.

-v2: According to Jesse, adding one CONFIG option for distribution to
     disable it or enable it.
-v3: update Kconfig text (jbarnes)

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

2 files changed, 41 insertions, 0 deletions

diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index 37856f7c7781..848bfb84c04c 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -31,6 +31,19 @@ config PCI_DEBUG
 
           When in doubt, say N.
 
+config PCI_REALLOC_ENABLE_AUTO
+        bool "Enable PCI resource re-allocation detection"
+        depends on PCI
+        help
+          Say Y here if you want the PCI core to detect if PCI resource
+          re-allocation needs to be enabled. You can always use pci=realloc=on
+          or pci=realloc=off to override it.  Note this feature is a no-op
+          unless PCI_IOV support is also enabled; in that case it will
+          automatically re-allocate PCI resources if SR-IOV BARs have not
+          been allocated by the BIOS.
+
+          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 e21e1c237301..c9214a14b49b 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;