Page mapping could overwritten by an accident (a bug). We can catch this
case by checking 'VALID' bit of GART's page entry prior to mapping of a
page. Since that check introduces a small performance impact, it should be
enabled explicitly using new GART's kernel module 'debug' parameter.
Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
---
drivers/iommu/tegra-gart.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/drivers/iommu/tegra-gart.c b/drivers/iommu/tegra-gart.c
index b62f790ad1ba..4c0abdcd1ad2 100644
--- a/drivers/iommu/tegra-gart.c
+++ b/drivers/iommu/tegra-gart.c
@@ -72,6 +72,8 @@ struct gart_domain {
static struct gart_device *gart_handle; /* unique for a system */
+static bool gart_debug;
+
#define GART_PTE(_pfn) \
(GART_ENTRY_PHYS_ADDR_VALID | ((_pfn) << PAGE_SHIFT))
@@ -271,6 +273,7 @@ static int gart_iommu_map(struct iommu_domain *domain, unsigned long iova,
struct gart_device *gart = gart_domain->gart;
unsigned long flags;
unsigned long pfn;
+ unsigned long pte;
if (!gart_iova_range_valid(gart, iova, bytes))
return -EINVAL;
@@ -282,6 +285,14 @@ static int gart_iommu_map(struct iommu_domain *domain, unsigned long iova,
spin_unlock_irqrestore(&gart->pte_lock, flags);
return -EINVAL;
}
+ if (gart_debug) {
+ pte = gart_read_pte(gart, iova);
+ if (pte & GART_ENTRY_PHYS_ADDR_VALID) {
+ spin_unlock_irqrestore(&gart->pte_lock, flags);
+ dev_err(gart->dev, "Page entry is in-use\n");
+ return -EBUSY;
+ }
+ }
gart_set_pte(gart, iova, GART_PTE(pfn));
FLUSH_GART_REGS(gart);
spin_unlock_irqrestore(&gart->pte_lock, flags);
@@ -515,7 +526,9 @@ static void __exit tegra_gart_exit(void)
subsys_initcall(tegra_gart_init);
module_exit(tegra_gart_exit);
+module_param(gart_debug, bool, 0644);
+MODULE_PARM_DESC(gart_debug, "Enable GART debugging");
MODULE_DESCRIPTION("IOMMU API for GART in Tegra20");
MODULE_AUTHOR("Hiroshi DOYU <hdoyu@xxxxxxxxxx>");
MODULE_ALIAS("platform:tegra-gart");
--
2.16.3
--
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