From d73a6d722a675dbba8f6b52c964a7076a24a12c1 Mon Sep 17 00:00:00 2001
From: Joerg Roedel <jroedel@suse.de>
Date: Fri, 20 Jun 2014 16:14:22 +0200
Subject: [PATCH] iommu/amd: Fix small race between invalidate_range_end/start

Commit e79df31 introduced mmu_notifer_count to protect
against parallel mmu_notifier_invalidate_range_start/end
calls. The patch left a small race condition when
invalidate_range_end() races with a new
invalidate_range_start() the empty page-table may be
reverted leading to stale TLB entries in the IOMMU and the
device. Use a spin_lock instead of just an atomic variable
to eliminate the race.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
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