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iommu/vt-d: use dedicated bitmap to track remapping entry allocation status

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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 observers 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@huawei.com>
Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>
This commit is contained in:
Jiang Liu 2014-01-06 14:18:08 +08:00 committed by Joerg Roedel
parent dbad086433
commit 360eb3c568
2 changed files with 27 additions and 29 deletions
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55
drivers/iommu/intel_irq_remapping.c
View File

@ -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) {
pr_warn("IR%d: can't allocate an IRTE\n", iommu->seq_id);
} 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);
@ -464,13 +451,23 @@ static int intel_setup_irq_remapping(struct intel_iommu *iommu, int mode)
INTR_REMAP_PAGE_ORDER);
if (!pages) {
printk(KERN_ERR "failed to allocate pages of order %d\n",
INTR_REMAP_PAGE_ORDER);
pr_err("IR%d: failed to allocate pages of order %d\n",
iommu->seq_id, INTR_REMAP_PAGE_ORDER);
kfree(iommu->ir_table);
return -ENOMEM;
}
bitmap = kcalloc(BITS_TO_LONGS(INTR_REMAP_TABLE_ENTRIES),
sizeof(long), GFP_ATOMIC);
if (bitmap == NULL) {
pr_err("IR%d: failed to allocate bitmap\n", iommu->seq_id);
__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;

1
include/linux/intel-iommu.h
View File

@ -288,6 +288,7 @@ struct q_inval {
struct ir_table {
struct irte *base;
unsigned long *bitmap;
};
#endif