Use cpu_relax in poll loop in GART IOMMU

The code waits for the GART to clear the TLB flush bit. Use cpu_relax
in this time to allow hypervisors to yield the CPU in this time.

Signed-off-by: Andi Kleen <ak@suse.de>

---
 arch/x86_64/kernel/pci-gart.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

Index: linux/arch/x86_64/kernel/pci-gart.c
===================================================================
--- linux.orig/arch/x86_64/kernel/pci-gart.c
+++ linux/arch/x86_64/kernel/pci-gart.c
@@ -148,9 +148,12 @@ static void flush_gart(struct device *de
 			if (!northbridges[i])
 				continue;
 			/* Make sure the hardware actually executed the flush. */
-			do { 
+			for (;;) { 
 				pci_read_config_dword(northbridges[i], 0x9c, &w);
-			} while (w & 1);
+				if (!(w & 1))
+					break;
+				cpu_relax();
+			}
 		} 
 		if (!flushed) 
 			printk("nothing to flush?\n");