[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>

Documentation/kernel-parameters.txt

@@ -1240,7 +1240,11 @@ running once the system is up.
 				bootloader. This is currently used on
 				IXP2000 systems where the bus has to be
 				configured a certain way for adjunct CPUs.
-
+		noearly		[X86] Don't do any early type 1 scanning.
+				This might help on some broken boards which
+				machine check when some devices' config space
+				is read. But various workarounds are disabled
+				and some IOMMU drivers will not work.
 	pcmv=		[HW,PCMCIA] BadgePAD 4
 
 	pd.		[PARIDE]

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++) {

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;

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;
+}

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

arch/x86_64/kernel/aperture.c

@@ -212,7 +212,7 @@ void __init iommu_hole_init(void)
 	u64 aper_base, last_aper_base = 0;
 	int valid_agp = 0;
 
-	if (iommu_aperture_disabled || !fix_aperture)
+	if (iommu_aperture_disabled || !fix_aperture || !early_pci_allowed())
 		return;
 
 	printk("Checking aperture...\n"); 

arch/x86_64/kernel/early-quirks.c

@@ -82,6 +82,10 @@ static struct chipset early_qrk[] = {
 void __init early_quirks(void)
 {
 	int num, slot, func;
+
+	if (!early_pci_allowed())
+		return;
+
 	/* Poor man's PCI discovery */
 	for (num = 0; num < 32; num++) {
 		for (slot = 0; slot < 32; slot++) {

arch/x86_64/kernel/pci-calgary.c

@@ -924,6 +924,9 @@ void __init detect_calgary(void)
 	if (swiotlb || no_iommu || iommu_detected)
 		return;
 
+	if (!early_pci_allowed())
+		return;
+
 	specified_table_size = determine_tce_table_size(end_pfn * PAGE_SIZE);
 
 	for (bus = 0; bus < MAX_PHB_BUS_NUM; bus++) {

arch/x86_64/kernel/vsmp.c

@@ -20,6 +20,9 @@ static int __init vsmp_init(void)
 	void *address;
 	unsigned int cap, ctl;
 
+	if (!early_pci_allowed())
+		return 0;
+
 	/* Check if we are running on a ScaleMP vSMP box */
 	if ((read_pci_config_16(0, 0x1f, 0, PCI_VENDOR_ID) != PCI_VENDOR_ID_SCALEMP) ||
 	    (read_pci_config_16(0, 0x1f, 0, PCI_DEVICE_ID) != PCI_DEVICE_ID_SCALEMP_VSMP_CTL))

arch/x86_64/mm/k8topology.c

@@ -54,6 +54,9 @@ int __init k8_scan_nodes(unsigned long start, unsigned long end)
 
 	nodes_clear(nodes_parsed);
 
+	if (!early_pci_allowed())
+		return -1;
+
 	nb = find_northbridge(); 
 	if (nb < 0) 
 		return nb;

drivers/pci/pci.c

@@ -953,13 +953,12 @@ static int __devinit pci_setup(char *str)
 		}
 		str = k;
 	}
-	return 1;
+	return 0;
 }
+early_param("pci", pci_setup);
 
 device_initcall(pci_init);
 
-__setup("pci=", pci_setup);
-
 #if defined(CONFIG_ISA) || defined(CONFIG_EISA)
 /* FIXME: Some boxes have multiple ISA bridges! */
 struct pci_dev *isa_bridge;

include/asm-x86_64/pci-direct.h

@@ -11,4 +11,6 @@ extern u8 read_pci_config_byte(u8 bus, u8 slot, u8 func, u8 offset);
 extern u16 read_pci_config_16(u8 bus, u8 slot, u8 func, u8 offset);
 extern void write_pci_config(u8 bus, u8 slot, u8 func, u8 offset, u32 val);
 
+extern int early_pci_allowed(void);
+
 #endif