[PATCH] x86_64: 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>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/x86_64/kernel/pci-gart.c b/arch/x86_64/kernel/pci-gart.c
index 0c3f052..ebd125e 100644
--- a/arch/x86_64/kernel/pci-gart.c
+++ b/arch/x86_64/kernel/pci-gart.c
@@ -148,9 +148,12 @@
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");