x86/pci: remove rounding quirk from e820_setup_gap()

Now that the e820 code explicitly reserves 'potentially dangerous'
free physical memory address space to protect ACPI stolen RAM,
there's no need for the rounding quirk in the PCI allocator anymore.

Also, this quirk was open-ended iteration that could end up reserving
a lot of free space and potentially breaking drivers - such as the one
reported by Yannick Roehlly <yannick.roehlly@free.fr> where there's
a PCI device with a large memory resource.

So remove it.

[ Impact: make more of the PCI hole available for assigning pci devices ]
Reported-by: NYannick Roehlly <yannick.roehlly@free.fr>
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Acked-by: NJesse Barnes <jesse.barnes@intel.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <4A01A7C8.5090701@kernel.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/e820.c

@@ -617,7 +617,7 @@ __init int e820_search_gap(unsigned long *gapstart, unsigned long *gapsize,
  */
 __init void e820_setup_gap(void)
 {
-	unsigned long gapstart, gapsize, round;
+	unsigned long gapstart, gapsize;
 	int found;
 
 	gapstart = 0x10000000;
@@ -635,14 +635,9 @@ __init void e820_setup_gap(void)
 #endif
 
 	/*
-	 * See how much we want to round up: start off with
-	 * rounding to the next 1MB area.
+	 * e820_reserve_resources_late protect stolen RAM already
 	 */
-	round = 0x100000;
-	while ((gapsize >> 4) > round)
-		round += round;
-	/* Fun with two's complement */
-	pci_mem_start = (gapstart + round) & -round;
+	pci_mem_start = gapstart;
 
 	printk(KERN_INFO
 	       "Allocating PCI resources starting at %lx (gap: %lx:%lx)\n",