From: Michal Schmidt <mschmidt@redhat.com>
Date: Tue, 28 Aug 2007 17:16:17 +0200
Subject: [x86_64] 'ide0=noprobe' crashes the kernel
Message-id: 46D43C41.8050807@redhat.com
O-Subject: [RHEL5.2 PATCH] "ide0=noprobe" crashes the kernel early
Bugzilla: 241338

BZ: https://bugzilla.redhat.com/show_bug.cgi?id=241338

Description: x86_64 kernel crashes early during boot when "ide0=noprobe"
parameter is passed on the command line.
The crash is caused by ide_setup() enabling interrupts inadvertently:

ide_setup()
  init_ide_data()
    init_hwif_default()
      ide_default_io_base()
	pci_find_device()

pci_find_device() uses a rwsem. Unlike i386, x86_64 uses
GENERIC_RWSEM_SPINLOCK implementation which enables interrupts.
The bug was spotted and analyzed by Gerd Hoffmann on a Xen HVM machine.

Solution: IDE just needs to know whether there are any PCI devices in
the system. The patch introduces a new function no_pci_devices() to
provide the answer. This avoids the call to pci_find_device().

Upstream status: The patch is upstream since commit
ed4aaadb1a7913f509f05d3e67840541a180713f ('fix jvc cdrom drive lockup'),
released in 2.6.23-rc1.

KABI impact: This adds a new exported function
int no_pci_devices(void);
EXPORT_SYMBOL(no_pci_devices);

Testing: Gerd Hoffmann confirmed a kernel with this patch fixed the bug.

Thanks,
Michal

Acked-by: Prarit Bhargava <prarit@redhat.com>
Acked-by: Don Dutile <ddutile@redhat.com>
Acked-by: Jarod Wilson <jwilson@redhat.com>
Acked-by: Prarit Bhargava <prarit@redhat.com>

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 773557e..db714a8 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -22,6 +22,18 @@ EXPORT_SYMBOL(pci_root_buses);
 
 LIST_HEAD(pci_devices);
 
+/*
+ * Some device drivers need know if pci is initiated.
+ * Basically, we think pci is not initiated when there
+ * is no device in list of pci_devices.
+ */
+int no_pci_devices(void)
+{
+	return list_empty(&pci_devices);
+}
+
+EXPORT_SYMBOL(no_pci_devices);
+
 #ifdef HAVE_PCI_LEGACY
 /**
  * pci_create_legacy_files - create legacy I/O port and memory files
diff --git a/include/asm-i386/ide.h b/include/asm-i386/ide.h
index 73465d2..e7817a3 100644
--- a/include/asm-i386/ide.h
+++ b/include/asm-i386/ide.h
@@ -46,7 +46,7 @@ static __inline__ unsigned long ide_default_io_base(int index)
 	 *	defined compatibility mode ports for PCI. A user can 
 	 *	override this using ide= but we must default safe.
 	 */
-	if (pci_find_device(PCI_ANY_ID, PCI_ANY_ID, NULL) == NULL) {
+	if (no_pci_devices()) {
 		switch(index) {
 			case 2: return 0x1e8;
 			case 3: return 0x168;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 694c4d8..3b2bcb1 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -431,6 +431,8 @@ extern struct bus_type pci_bus_type;
  * code, or pci core code. */
 extern struct list_head pci_root_buses;	/* list of all known PCI buses */
 extern struct list_head pci_devices;	/* list of all devices */
+/* Some device drivers need know if pci is initiated */
+extern int no_pci_devices(void);
 
 void pcibios_fixup_bus(struct pci_bus *);
 int pcibios_enable_device(struct pci_dev *, int mask);
@@ -705,6 +707,7 @@ static inline struct pci_dev *pci_get_class(unsigned int class, struct pci_dev *
 { return NULL; }
 
 #define pci_dev_present(ids)	(0)
+#define no_pci_devices()	(1)
 #define pci_dev_put(dev)	do { } while (0)
 
 static inline void pci_set_master(struct pci_dev *dev) { }