[PATCH] x86: Allow disabling early pci scans with pci=noearly or disallowing conf1

Some buggy systems can machine check when config space accesses
happen for some non existent devices.  i386/x86-64 do some early
device scans that might trigger this. Allow pci=noearly to disable
this. Also when type 1 is disabling also don't do any early
accesses which are always type1.

This moves the pci= configuration parsing to be a early parameter.
I don't think this can break anything because it only changes
a single global that is only used by PCI.

Cc: gregkh@suse.de
Cc: Trammell Hudson <hudson@osresearch.net>

Signed-off-by: Andi Kleen <ak@suse.de>

4 files changed, 18 insertions, 1 deletions

diff --git a/arch/i386/kernel/acpi/earlyquirk.c b/arch/i386/kernel/acpi/earlyquirk.c
index 1649a175a206..fe799b11ac0a 100644
--- a/arch/i386/kernel/acpi/earlyquirk.c
+++ b/arch/i386/kernel/acpi/earlyquirk.c
@@ -48,7 +48,11 @@ void __init check_acpi_pci(void)
         int num, slot, func;
 
         /* Assume the machine supports type 1. If not it will 
-           always read ffffffff and should not have any side effect. */
+           always read ffffffff and should not have any side effect.
+           Actually a few buggy systems can machine check. Allow the user
+           to disable it by command line option at least -AK */
+        if (!early_pci_allowed())
+                return;
 
         /* Poor man's PCI discovery */
         for (num = 0; num < 32; num++) {
diff --git a/arch/i386/pci/common.c b/arch/i386/pci/common.c
index 0a362e3aeac5..68bce194e688 100644
--- a/arch/i386/pci/common.c
+++ b/arch/i386/pci/common.c
@@ -242,6 +242,10 @@ char * __devinit  pcibios_setup(char *str)
                 acpi_noirq_set();
                 return NULL;
         }
+        else if (!strcmp(str, "noearly")) {
+                pci_probe |= PCI_PROBE_NOEARLY;
+                return NULL;
+        }
 #ifndef CONFIG_X86_VISWS
         else if (!strcmp(str, "usepirqmask")) {
                 pci_probe |= PCI_USE_PIRQ_MASK;
diff --git a/arch/i386/pci/early.c b/arch/i386/pci/early.c
index b1f7f40d809b..713d6c866cae 100644
--- a/arch/i386/pci/early.c
+++ b/arch/i386/pci/early.c
@@ -1,6 +1,8 @@
 #include <linux/kernel.h>
+#include <linux/pci.h>
 #include <asm/pci-direct.h>
 #include <asm/io.h>
+#include "pci.h"
 
 /* Direct PCI access. This is used for PCI accesses in early boot before
    the PCI subsystem works. */
@@ -42,3 +44,9 @@ void write_pci_config(u8 bus, u8 slot, u8 func, u8 offset,
         outl(0x80000000 | (bus<<16) | (slot<<11) | (func<<8) | offset, 0xcf8);
         outl(val, 0xcfc);
 }
+
+int early_pci_allowed(void)
+{
+        return (pci_probe & (PCI_PROBE_CONF1|PCI_PROBE_NOEARLY)) ==
+                        PCI_PROBE_CONF1;
+}
diff --git a/arch/i386/pci/pci.h b/arch/i386/pci/pci.h
index 8a7cf1f23684..1814f74569c6 100644
--- a/arch/i386/pci/pci.h
+++ b/arch/i386/pci/pci.h
@@ -17,6 +17,7 @@
 #define PCI_PROBE_CONF2         0x0004
 #define PCI_PROBE_MMCONF        0x0008
 #define PCI_PROBE_MASK          0x000f
+#define PCI_PROBE_NOEARLY       0x0010
 
 #define PCI_NO_SORT             0x0100
 #define PCI_BIOS_SORT           0x0200