[PATCH] x86_64: Use the e820 hole to map the IOMMU/AGP aperture

This might save memory on some Opteron systems without AGP bridge.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 30 insertions, 11 deletions

diff --git a/arch/x86_64/kernel/aperture.c b/arch/x86_64/kernel/aperture.c
index 4baa99fe1e5c..a491f72cc966 100644
--- a/arch/x86_64/kernel/aperture.c
+++ b/arch/x86_64/kernel/aperture.c
@@ -33,11 +33,13 @@ int fallback_aper_force __initdata = 0;
 
 int fix_aperture __initdata = 1;
 
-/* This code runs before the PCI subsystem is initialized, so just 
-   access the northbridge directly. */
-
 #define NB_ID_3 (PCI_VENDOR_ID_AMD | (0x1103<<16))
 
+static struct resource aper_res = {
+        .name = "Aperture",
+        .flags = IORESOURCE_MEM,
+};
+
 static u32 __init allocate_aperture(void) 
 {
 #ifdef CONFIG_DISCONTIGMEM
@@ -53,11 +55,24 @@ static u32 __init allocate_aperture(void)
         aper_size = (32 * 1024 * 1024) << fallback_aper_order; 
 
         /* 
-         * Aperture has to be naturally aligned. This means an 2GB aperture won't 
-         * have much chances to find a place in the lower 4GB of memory. 
-         * Unfortunately we cannot move it up because that would make the 
-         * IOMMU useless.
+         * Aperture has to be naturally aligned. This means an 2GB
+         * aperture won't have much chances to find a place in the
+         * lower 4GB of memory.  Unfortunately we cannot move it up
+         * because that would make the IOMMU useless.
          */
+
+        /* First try to find some free unused space */
+        if (!allocate_resource(&iomem_resource, &aper_res,
+                               aper_size,
+                               0, 0xffffffff,
+                               aper_size,
+                               NULL, NULL)) {
+                printk(KERN_INFO "Putting aperture at %lx-%lx\n",
+                       aper_res.start, aper_res.end);
+                return aper_res.start;
+        }
+
+        /* No free space found. Go on to waste some memory... */
         p = __alloc_bootmem_node(nd0, aper_size, aper_size, 0); 
         if (!p || __pa(p)+aper_size > 0xffffffff) {
                 printk("Cannot allocate aperture memory hole (%p,%uK)\n",
@@ -66,7 +81,7 @@ static u32 __init allocate_aperture(void)
                         free_bootmem_node(nd0, (unsigned long)p, aper_size); 
                 return 0;
         }
-        printk("Mapping aperture over %d KB of RAM @ %lx\n",  
+        printk("Mapping aperture over %d KB of precious RAM @ %lx\n",
                aper_size >> 10, __pa(p)); 
         return (u32)__pa(p); 
 }
@@ -87,10 +102,16 @@ static int __init aperture_valid(char *name, u64 aper_base, u32 aper_size)
                 printk("Aperture from %s pointing to e820 RAM. Ignoring.\n",name);
                 return 0; 
         } 
+        /* Don't check the resource here because the aperture is usually
+           in an e820 reserved area, and we allocated these earlier. */
         return 1;
 } 
 
-/* Find a PCI capability */ 
+/*
+ * Find a PCI capability.
+ * This code runs before the PCI subsystem is initialized, so just
+ * access the northbridge directly.
+ */
 static __u32 __init find_cap(int num, int slot, int func, int cap) 
 { 
         u8 pos;
@@ -255,8 +276,6 @@ void __init iommu_hole_init(void)
                    fallback_aper_force) { 
                 printk("Your BIOS doesn't leave a aperture memory hole\n");
                 printk("Please enable the IOMMU option in the BIOS setup\n");
-                printk("This costs you %d MB of RAM\n",
-                       32 << fallback_aper_order);
 
                 aper_order = fallback_aper_order;
                 aper_alloc = allocate_aperture();