[PATCH] i386/x86-64: Check that MCFG points to an e820 reserved area

This patch introduces a user for the e820_all_mapped function:

There have been several machines that don't have a working MMCONFIG,
often because of a buggy MCFG table in the ACPI bios.  This patch adds a
simple sanity check that detects a whole bunch of these cases, and when
it detects it, linux now boots rather than crash-and-burns.

The accuracy of this detection can in principle be improved if there was
a "is this entire range in e820 with THIS attribute", but no such
function exist and the complexity needed for this is not really worth
it; this simple check already catches most cases anyway.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/pci/mmconfig.c

@@ -12,8 +12,11 @@
 #include <linux/pci.h>
 #include <linux/init.h>
 #include <linux/acpi.h>
+#include <asm/e820.h>
 #include "pci.h"
 
+#define MMCONFIG_APER_SIZE (256*1024*1024)
+
 #define mmcfg_virt_addr ((void __iomem *) fix_to_virt(FIX_PCIE_MCFG))
 
 /* The base address of the last MMCONFIG device accessed */
@@ -183,6 +186,14 @@ void __init pci_mmcfg_init(void)
 	    (pci_mmcfg_config[0].base_address == 0))
 		return;
 
+	if (!e820_all_mapped(pci_mmcfg_config[0].base_address,
+			pci_mmcfg_config[0].base_address + MMCONFIG_APER_SIZE,
+			E820_RESERVED)) {
+		printk(KERN_ERR "PCI: BIOS Bug: MCFG area is not E820-reserved\n");
+		printk(KERN_ERR "PCI: Not using MMCONFIG.\n");
+		return;
+	}
+
 	printk(KERN_INFO "PCI: Using MMCONFIG\n");
 	raw_pci_ops = &pci_mmcfg;
 	pci_probe = (pci_probe & ~PCI_PROBE_MASK) | PCI_PROBE_MMCONF;

arch/x86_64/pci/mmconfig.c

@@ -9,6 +9,8 @@
 #include <linux/init.h>
 #include <linux/acpi.h>
 #include <linux/bitmap.h>
+#include <asm/e820.h>
+
 #include "pci.h"
 
 #define MMCONFIG_APER_SIZE (256*1024*1024)
@@ -161,6 +163,14 @@ void __init pci_mmcfg_init(void)
 	    (pci_mmcfg_config[0].base_address == 0))
 		return;
 
+	if (!e820_all_mapped(pci_mmcfg_config[0].base_address,
+			pci_mmcfg_config[0].base_address + MMCONFIG_APER_SIZE,
+			E820_RESERVED)) {
+		printk(KERN_ERR "PCI: BIOS Bug: MCFG area is not E820-reserved\n");
+		printk(KERN_ERR "PCI: Not using MMCONFIG.\n");
+		return;
+	}
+
 	/* RED-PEN i386 doesn't do _nocache right now */
 	pci_mmcfg_virt = kmalloc(sizeof(*pci_mmcfg_virt) * pci_mmcfg_config_num, GFP_KERNEL);
 	if (pci_mmcfg_virt == NULL) {