From 85f9eebccde51e24896f31383f5b70776362e1a6 Mon Sep 17 00:00:00 2001
From: Andi Kleen <ak@suse.de>
Date: Sat, 25 Mar 2006 16:29:37 +0100
Subject: [PATCH] [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>
---
arch/x86_64/kernel/pci-gart.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/x86_64/kernel/pci-gart.c b/arch/x86_64/kernel/pci-gart.c
index 0c3f052ba6ceb..ebd125e968bed 100644
--- a/arch/x86_64/kernel/pci-gart.c
+++ b/arch/x86_64/kernel/pci-gart.c
@@ -148,9 +148,12 @@ static void flush_gart(struct device *dev)
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");
--
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