PCI: conditional resource-reallocation through kernel parameter pci=realloc

    
Multiple attempts to dynamically reallocate pci resources have
unfortunately lead to regressions. Though we continue to fix the
regressions and fine tune the dynamic-reallocation behavior, we have not
reached a acceptable state yet.
    
This patch provides a interim solution. It disables dynamic reallocation
by default, but adds the ability to enable it through pci=realloc kernel
command line parameter.
    
Tested-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

3 files changed, 19 insertions, 0 deletions

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 2c5b9b991279..692671b11667 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3483,6 +3483,8 @@ static int __init pci_setup(char *str)
                                 pci_no_msi();
                         } else if (!strcmp(str, "noaer")) {
                                 pci_no_aer();
+                        } else if (!strncmp(str, "realloc", 7)) {
+                                pci_realloc();
                         } else if (!strcmp(str, "nodomains")) {
                                 pci_no_domains();
                         } else if (!strncmp(str, "cbiosize=", 9)) {
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 731e20265ace..3a39bf1f1e2c 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -146,6 +146,8 @@ static inline void pci_no_msi(void) { }
 static inline void pci_msi_init_pci_dev(struct pci_dev *dev) { }
 #endif
 
+extern void pci_realloc(void);
+
 static inline int pci_no_d1d2(struct pci_dev *dev)
 {
         unsigned int parent_dstates = 0;
diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 1e9e5a5b8c81..9995842e45b5 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -47,6 +47,13 @@ struct resource_list_x {
         (head)->next = NULL;                            \
 } while (0)
 
+int pci_realloc_enable = 0;
+#define pci_realloc_enabled() pci_realloc_enable
+void pci_realloc(void)
+{
+        pci_realloc_enable = 1;
+}
+
 /**
  * add_to_list() - add a new resource tracker to the list
  * @head:       Head of the list
@@ -1025,6 +1032,7 @@ static int __init pci_get_max_depth(void)
         return depth;
 }
 
+
 /*
  * first try will not touch pci bridge res
  * second  and later try will clear small leaf bridge res
@@ -1068,6 +1076,13 @@ again:
         /* any device complain? */
         if (!head.next)
                 goto enable_and_dump;
+
+        /* don't realloc if asked to do so */
+        if (!pci_realloc_enabled()) {
+                free_list(resource_list_x, &head);
+                goto enable_and_dump;
+        }
+
         failed_type = 0;
         for (list = head.next; list;) {
                 failed_type |= list->flags;