Commit 5b201927 authored by Mike Waychison's avatar Mike Waychison Committed by Linus Torvalds
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[PATCH] x86_64: Fix a race in the free_iommu path 



We do this by removing a micro-optimization that tries to avoid grabbing
the iommu_bitmap_lock spinlock and using a bus-locked operation.

This still races with other simultaneous alloc_iommu or free_iommu(size >
1) which both use bus-unlocked operations.

The end result of this race is eventually ending up with an
iommu_gart_bitmap that has bits errornously set all over, making large
contiguous iommu space allocations fail with 'PCI-DMA: Out of IOMMU space'.

Signed-off-by: default avatarMike Waychison <mikew@google.com>
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent ddbe3eec

arch/x86_64/kernel/pci-gart.c

+0 −4
Original line number Diff line number Diff line
@@ -112,10 +112,6 @@ static unsigned long alloc_iommu(int size) 
static void free_iommu(unsigned long offset, int size)

{ 

	unsigned long flags;

	if (size == 1) { 

		clear_bit(offset, iommu_gart_bitmap); 

		return;

	}

	spin_lock_irqsave(&iommu_bitmap_lock, flags);

	__clear_bit_string(iommu_gart_bitmap, offset, size);

	spin_unlock_irqrestore(&iommu_bitmap_lock, flags);