[PATCH] x86: Revert e820 MCFG heuristics

The check for the MCFG table being reserved in the e820 map was originally
added to detect a broken BIOS in a preproduction Intel SDV. However it also
breaks the Apple x86 Macs, which can't supply this properly, but need
a working MCFG. With this patch they wouldn't use the MCFG and not work.

After some discussion I think it's best to remove the heuristic again.
It also failed on some other boxes (although it didn't cause much
problems there because old style port access for PCI config space
still works as fallback), but the preproduction SDVs can just use
pci=nommcfg. Supporting production machines properly is more
important.

Edgar Hucek did all the debugging work.

Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Edgar Hucek <hostmaster@ed-soft.at>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/kernel/setup.c

@@ -956,38 +956,6 @@ efi_memory_present_wrapper(unsigned long start, unsigned long end, void *arg)
 	return 0;
 }
 
- /*
-  * This function checks if the entire range <start,end> is mapped with type.
-  *
-  * Note: this function only works correct if the e820 table is sorted and
-  * not-overlapping, which is the case
-  */
-int __init
-e820_all_mapped(unsigned long s, unsigned long e, unsigned type)
-{
-	u64 start = s;
-	u64 end = e;
-	int i;
-	for (i = 0; i < e820.nr_map; i++) {
-		struct e820entry *ei = &e820.map[i];
-		if (type && ei->type != type)
-			continue;
-		/* is the region (part) in overlap with the current region ?*/
-		if (ei->addr >= end || ei->addr + ei->size <= start)
-			continue;
-		/* if the region is at the beginning of <start,end> we move
-		 * start to the end of the region since it's ok until there
-		 */
-		if (ei->addr <= start)
-			start = ei->addr + ei->size;
-		/* if start is now at or beyond end, we're done, full
-		 * coverage */
-		if (start >= end)
-			return 1; /* we're done */
-	}
-	return 0;
-}
-
 /*
  * Find the highest page frame number we have available
  */

arch/i386/pci/mmconfig.c

@@ -198,15 +198,6 @@ 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_MIN,
-			E820_RESERVED)) {
-		printk(KERN_ERR "PCI: BIOS Bug: MCFG area at %x is not E820-reserved\n",
-				pci_mmcfg_config[0].base_address);
-		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/kernel/e820.c

@@ -104,35 +104,6 @@ e820_any_mapped(unsigned long start, unsigned long end, unsigned type)
 	return 0;
 }
 
-/*
- * This function checks if the entire range <start,end> is mapped with type.
- *
- * Note: this function only works correct if the e820 table is sorted and
- * not-overlapping, which is the case
- */
-int __init e820_all_mapped(unsigned long start, unsigned long end, unsigned type)
-{
-	int i;
-	for (i = 0; i < e820.nr_map; i++) {
-		struct e820entry *ei = &e820.map[i];
-		if (type && ei->type != type)
-			continue;
-		/* is the region (part) in overlap with the current region ?*/
-		if (ei->addr >= end || ei->addr + ei->size <= start)
-			continue;
-
-		/* if the region is at the beginning of <start,end> we move
-		 * start to the end of the region since it's ok until there
-		 */
-		if (ei->addr <= start)
-			start = ei->addr + ei->size;
-		/* if start is now at or beyond end, we're done, full coverage */
-		if (start >= end)
-			return 1; /* we're done */
-	}
-	return 0;
-}
-
 /* 
  * Find a free area in a specific range. 
  */ 

arch/x86_64/pci/mmconfig.c

@@ -177,15 +177,6 @@ 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_MIN,
-			E820_RESERVED)) {
-		printk(KERN_ERR "PCI: BIOS Bug: MCFG area at %x is not E820-reserved\n",
-				pci_mmcfg_config[0].base_address);
-		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) {