x86_64: allocate gart aperture from 512M

because we try to reserve dma32 early, so we have chance to get aperture
from 64M.

with some sequence aperture allocated from RAM, could become E820_RESERVED.

and then if doing a kexec with a big kernel that uncompressed size is above
64M we could have a range conflict with still using gart.

So allocate gart aperture from 512M instead.

Also change the fallback_aper_order to 5, because we don't have chance to get
2G or 4G aperture.

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 5 insertions, 1 deletions

diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 0c37f16b695..1a017f00e86 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -77,10 +77,14 @@ void __init dma32_reserve_bootmem(void)
         if (end_pfn <= MAX_DMA32_PFN)
                 return;
 
+        /*
+         * check aperture_64.c allocate_aperture() for reason about
+         * using 512M as goal
+         */
         align = 64ULL<<20;
         size = round_up(dma32_bootmem_size, align);
         dma32_bootmem_ptr = __alloc_bootmem_nopanic(size, align,
-                                 __pa(MAX_DMA_ADDRESS));
+                                 512ULL<<20);
         if (dma32_bootmem_ptr)
                 dma32_bootmem_size = size;
         else