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Commit 85f9eebc authored by Andi Kleen's avatar Andi Kleen Committed by Linus Torvalds
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[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: default avatarAndi Kleen <ak@suse.de>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 77d910f5

arch/x86_64/kernel/pci-gart.c

+5 −2
Original line number Original line Diff line number Diff line
@@ -148,9 +148,12 @@ static void flush_gart(struct device *dev) 
			if (!northbridges[i])

			if (!northbridges[i])

				continue;

				continue;

			/* Make sure the hardware actually executed the flush. */

			/* Make sure the hardware actually executed the flush. */

			do { 

			for (;;) { 

				pci_read_config_dword(northbridges[i], 0x9c, &w);

				pci_read_config_dword(northbridges[i], 0x9c, &w);

			} while (w & 1);

				if (!(w & 1))

					break;

				cpu_relax();

			}

		} 

		} 

		if (!flushed) 

		if (!flushed) 

			printk("nothing to flush?\n");

			printk("nothing to flush?\n");