65 lines
2.5 KiB
Diff
65 lines
2.5 KiB
Diff
From 9a0bd2ce954a8033987b9b3118ee8bccabb0b8f2 Mon Sep 17 00:00:00 2001
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Date: Thu, 15 Sep 2016 17:16:44 +0200
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Subject: [PATCH 038/365] iommu/vt-d: don't disable preemption while accessing
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deferred_flush()
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get_cpu() disables preemption and returns the current CPU number. The
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CPU number is later only used once while retrieving the address of the
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local's CPU deferred_flush pointer.
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We can instead use raw_cpu_ptr() while we remain preemptible. The worst
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thing that can happen is that flush_unmaps_timeout() is invoked multiple
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times: once by taskA after seeing HIGH_WATER_MARK and then preempted to
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another CPU and then by taskB which saw HIGH_WATER_MARK on the same CPU
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as taskA. It is also likely that ->size got from HIGH_WATER_MARK to 0
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right after its read because another CPU invoked flush_unmaps_timeout()
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for this CPU.
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The access to flush_data is protected by a spinlock so even if we get
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migrated to another CPU or preempted - the data structure is protected.
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While at it, I marked deferred_flush static since I can't find a
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reference to it outside of this file.
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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drivers/iommu/intel-iommu.c | 8 ++------
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1 file changed, 2 insertions(+), 6 deletions(-)
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diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
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index 593a4bfcba42..fa7d78442ee7 100644
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--- a/drivers/iommu/intel-iommu.c
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+++ b/drivers/iommu/intel-iommu.c
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@@ -480,7 +480,7 @@ struct deferred_flush_data {
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struct deferred_flush_table *tables;
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};
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-DEFINE_PER_CPU(struct deferred_flush_data, deferred_flush);
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+static DEFINE_PER_CPU(struct deferred_flush_data, deferred_flush);
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/* bitmap for indexing intel_iommus */
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static int g_num_of_iommus;
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@@ -3742,10 +3742,8 @@ static void add_unmap(struct dmar_domain *dom, unsigned long iova_pfn,
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struct intel_iommu *iommu;
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struct deferred_flush_entry *entry;
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struct deferred_flush_data *flush_data;
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- unsigned int cpuid;
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- cpuid = get_cpu();
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- flush_data = per_cpu_ptr(&deferred_flush, cpuid);
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+ flush_data = raw_cpu_ptr(&deferred_flush);
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/* Flush all CPUs' entries to avoid deferring too much. If
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* this becomes a bottleneck, can just flush us, and rely on
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@@ -3778,8 +3776,6 @@ static void add_unmap(struct dmar_domain *dom, unsigned long iova_pfn,
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}
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flush_data->size++;
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spin_unlock_irqrestore(&flush_data->lock, flags);
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-
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- put_cpu();
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}
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static void intel_unmap(struct device *dev, dma_addr_t dev_addr, size_t size)
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--
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2.28.0
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