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authorSebastian Andrzej Siewior <bigeasy@linutronix.de>2017-06-27 19:16:48 +0300
committerJoerg Roedel <jroedel@suse.de>2017-06-28 13:24:40 +0300
commit58c4a95f90839624b67f67acdb8a129f4383b569 (patch)
tree44e773e9f149411b27fe80cbfecb87fc78feb572 /drivers
parent71bb620df634b22a08efd62a0f93c3f2aceaa8e2 (diff)
downloadlinux-58c4a95f90839624b67f67acdb8a129f4383b569.tar.xz
iommu/vt-d: Don't disable preemption while accessing deferred_flush()
get_cpu() disables preemption and returns the current CPU number. The CPU number is only used once while retrieving the address of the local's CPU deferred_flush pointer. We can instead use raw_cpu_ptr() while we remain preemptible. The worst thing that can happen is that flush_unmaps_timeout() is invoked multiple times: once by taskA after seeing HIGH_WATER_MARK and then preempted to another CPU and then by taskB which saw HIGH_WATER_MARK on the same CPU as taskA. It is also likely that ->size got from HIGH_WATER_MARK to 0 right after its read because another CPU invoked flush_unmaps_timeout() for this CPU. The access to flush_data is protected by a spinlock so even if we get migrated to another CPU or preempted - the data structure is protected. While at it, I marked deferred_flush static since I can't find a reference to it outside of this file. Cc: David Woodhouse <dwmw2@infradead.org> Cc: Joerg Roedel <joro@8bytes.org> Cc: iommu@lists.linux-foundation.org Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Joerg Roedel <jroedel@suse.de>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/iommu/intel-iommu.c8
1 files changed, 2 insertions, 6 deletions
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index ee9c258d3ae0..0ca985b418ec 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -481,7 +481,7 @@ struct deferred_flush_data {
struct deferred_flush_table *tables;
};
-DEFINE_PER_CPU(struct deferred_flush_data, deferred_flush);
+static DEFINE_PER_CPU(struct deferred_flush_data, deferred_flush);
/* bitmap for indexing intel_iommus */
static int g_num_of_iommus;
@@ -3710,10 +3710,8 @@ static void add_unmap(struct dmar_domain *dom, unsigned long iova_pfn,
struct intel_iommu *iommu;
struct deferred_flush_entry *entry;
struct deferred_flush_data *flush_data;
- unsigned int cpuid;
- cpuid = get_cpu();
- flush_data = per_cpu_ptr(&deferred_flush, cpuid);
+ flush_data = raw_cpu_ptr(&deferred_flush);
/* Flush all CPUs' entries to avoid deferring too much. If
* this becomes a bottleneck, can just flush us, and rely on
@@ -3746,8 +3744,6 @@ static void add_unmap(struct dmar_domain *dom, unsigned long iova_pfn,
}
flush_data->size++;
spin_unlock_irqrestore(&flush_data->lock, flags);
-
- put_cpu();
}
static void intel_unmap(struct device *dev, dma_addr_t dev_addr, size_t size)