Currently Intel interrupt remapping drivers uses the "present" flag bit
in remapping entry to track whether an entry is allocated or not.
It works as follow:
1) allocate a remapping entry and set its "present" flag bit to 1
2) compose other fields for the entry
3) update the remapping entry with the composed value
The remapping hardware may access the entry between step 1 and step 3,
which then obervers an entry with the "present" flag set but random
values in all other fields.
This patch introduces a dedicated bitmap to track remapping entry
allocation status instead of sharing the "present" flag with hardware,
thus eliminate the race window. It also simplifies the implementation.
Tested-and-reviewed-by: Yijing Wang <wangyijing@xxxxxxxxxx>
Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxxxxxxx>
---
drivers/iommu/intel_irq_remapping.c | 51 +++++++++++++++++------------------
include/linux/intel-iommu.h | 1 +
2 files changed, 25 insertions(+), 27 deletions(-)
diff --git a/drivers/iommu/intel_irq_remapping.c b/drivers/iommu/intel_irq_remapping.c
index bab10b1..282d392 100644
--- a/drivers/iommu/intel_irq_remapping.c
+++ b/drivers/iommu/intel_irq_remapping.c
@@ -72,7 +72,6 @@ static int alloc_irte(struct intel_iommu *iommu, int irq, u16 count)
u16 index, start_index;
unsigned int mask = 0;
unsigned long flags;
- int i;
if (!count || !irq_iommu)
return -1;
@@ -96,32 +95,17 @@ static int alloc_irte(struct intel_iommu *iommu, int irq, u16 count)
}
raw_spin_lock_irqsave(&irq_2_ir_lock, flags);
- do {
- for (i = index; i < index + count; i++)
- if (table->base[i].present)
- break;
- /* empty index found */
- if (i == index + count)
- break;
-
- index = (index + count) % INTR_REMAP_TABLE_ENTRIES;
-
- if (index == start_index) {
- raw_spin_unlock_irqrestore(&irq_2_ir_lock, flags);
- printk(KERN_ERR "can't allocate an IRTE\n");
- return -1;
- }
- } while (1);
-
- for (i = index; i < index + count; i++)
- table->base[i].present = 1;
-
- cfg->remapped = 1;
- irq_iommu->iommu = iommu;
- irq_iommu->irte_index = index;
- irq_iommu->sub_handle = 0;
- irq_iommu->irte_mask = mask;
-
+ index = bitmap_find_free_region(table->bitmap,
+ INTR_REMAP_TABLE_ENTRIES, mask);
+ if (index < 0) {
+ printk(KERN_ERR "can't allocate an IRTE\n");
+ } else {
+ cfg->remapped = 1;
+ irq_iommu->iommu = iommu;
+ irq_iommu->irte_index = index;
+ irq_iommu->sub_handle = 0;
+ irq_iommu->irte_mask = mask;
+ }
raw_spin_unlock_irqrestore(&irq_2_ir_lock, flags);
return index;
@@ -254,6 +238,8 @@ static int clear_entries(struct irq_2_iommu *irq_iommu)
set_64bit(&entry->low, 0);
set_64bit(&entry->high, 0);
}
+ bitmap_release_region(iommu->ir_table->bitmap, index,
+ irq_iommu->irte_mask);
return qi_flush_iec(iommu, index, irq_iommu->irte_mask);
}
@@ -453,6 +439,7 @@ static int intel_setup_irq_remapping(struct intel_iommu *iommu, int mode)
{
struct ir_table *ir_table;
struct page *pages;
+ unsigned long *bitmap;
ir_table = iommu->ir_table = kzalloc(sizeof(struct ir_table),
GFP_ATOMIC);
@@ -470,7 +457,17 @@ static int intel_setup_irq_remapping(struct intel_iommu *iommu, int mode)
return -ENOMEM;
}
+ bitmap = kcalloc(BITS_TO_LONGS(INTR_REMAP_TABLE_ENTRIES),
+ sizeof(long), GFP_ATOMIC);
+ if (bitmap == NULL) {
+ printk(KERN_ERR "failed to allocate bitmap\n");
+ __free_pages(pages, INTR_REMAP_PAGE_ORDER);
+ kfree(ir_table);
+ return -ENOMEM;
+ }
+
ir_table->base = page_address(pages);
+ ir_table->bitmap = bitmap;
iommu_set_irq_remapping(iommu, mode);
return 0;
diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
index d380c5e..de1e5e9 100644
--- a/include/linux/intel-iommu.h
+++ b/include/linux/intel-iommu.h
@@ -288,6 +288,7 @@ struct q_inval {
struct ir_table {
struct irte *base;
+ unsigned long *bitmap;
};
#endif
--
1.7.10.4
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