[PATCH v2] iommu/tegra-smmu: Add missing locks around mapping operations

[PATCH v2] iommu/tegra-smmu: Add missing locks around mapping operations

[Dmitry Osipenko]

The mapping operations of the Tegra SMMU driver are subjected to a race
condition issues because SMMU Address Space isn't allocated and freed
atomically, while it should be. This patch makes the mapping operations
atomic, it fixes an accidentally released Host1x Address Space problem
which happens while running multiple graphics tests in parallel on
Tegra30, i.e. by having multiple threads racing with each other in the
Host1x's submission and completion code paths, performing IOVA mappings
and unmappings in parallel.

Cc: <stable@vger.kernel.org>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---

Changelog:

v2: - Now using mutex instead of spinlock.

    - The _locked postfix is replaced with the underscores prefix.

 drivers/iommu/tegra-smmu.c | 38 ++++++++++++++++++++++++++++++++++----
 1 file changed, 34 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c
index 7426b7666e2b..9cf06acb00ce 100644
--- a/drivers/iommu/tegra-smmu.c
+++ b/drivers/iommu/tegra-smmu.c
@@ -49,6 +49,7 @@ struct tegra_smmu_as {
 	struct iommu_domain domain;
 	struct tegra_smmu *smmu;
 	unsigned int use_count;
+	struct mutex lock;
 	u32 *count;
 	struct page **pts;
 	struct page *pd;
@@ -308,6 +309,8 @@ static struct iommu_domain *tegra_smmu_domain_alloc(unsigned type)
 		return NULL;
 	}
 
+	mutex_init(&as->lock);
+
 	/* setup aperture */
 	as->domain.geometry.aperture_start = 0;
 	as->domain.geometry.aperture_end = 0xffffffff;
@@ -655,8 +658,9 @@ static void tegra_smmu_set_pte(struct tegra_smmu_as *as, unsigned long iova,
 	smmu_flush(smmu);
 }
 
-static int tegra_smmu_map(struct iommu_domain *domain, unsigned long iova,
-			  phys_addr_t paddr, size_t size, int prot, gfp_t gfp)
+static int
+__tegra_smmu_map(struct iommu_domain *domain, unsigned long iova,
+		 phys_addr_t paddr, size_t size, int prot, gfp_t gfp)
 {
 	struct tegra_smmu_as *as = to_smmu_as(domain);
 	dma_addr_t pte_dma;
@@ -685,8 +689,9 @@ static int tegra_smmu_map(struct iommu_domain *domain, unsigned long iova,
 	return 0;
 }
 
-static size_t tegra_smmu_unmap(struct iommu_domain *domain, unsigned long iova,
-			       size_t size, struct iommu_iotlb_gather *gather)
+static size_t
+__tegra_smmu_unmap(struct iommu_domain *domain, unsigned long iova,
+		   size_t size, struct iommu_iotlb_gather *gather)
 {
 	struct tegra_smmu_as *as = to_smmu_as(domain);
 	dma_addr_t pte_dma;
@@ -702,6 +707,31 @@ static size_t tegra_smmu_unmap(struct iommu_domain *domain, unsigned long iova,
 	return size;
 }
 
+static int tegra_smmu_map(struct iommu_domain *domain, unsigned long iova,
+			  phys_addr_t paddr, size_t size, int prot, gfp_t gfp)
+{
+	struct tegra_smmu_as *as = to_smmu_as(domain);
+	int ret;
+
+	mutex_lock(&as->lock);
+	ret = __tegra_smmu_map(domain, iova, paddr, size, prot, gfp);
+	mutex_unlock(&as->lock);
+
+	return ret;
+}
+
+static size_t tegra_smmu_unmap(struct iommu_domain *domain, unsigned long iova,
+			       size_t size, struct iommu_iotlb_gather *gather)
+{
+	struct tegra_smmu_as *as = to_smmu_as(domain);
+
+	mutex_lock(&as->lock);
+	size = __tegra_smmu_unmap(domain, iova, size, gather);
+	mutex_unlock(&as->lock);
+
+	return size;
+}
+
 static phys_addr_t tegra_smmu_iova_to_phys(struct iommu_domain *domain,
 					   dma_addr_t iova)
 {
-- 
2.26.0

Re: [PATCH v2] iommu/tegra-smmu: Add missing locks around mapping operations

[Dmitry Osipenko]

25.05.2020 22:54, Dmitry Osipenko пишет:
> The mapping operations of the Tegra SMMU driver are subjected to a race
> condition issues because SMMU Address Space isn't allocated and freed
> atomically, while it should be. This patch makes the mapping operations
> atomic, it fixes an accidentally released Host1x Address Space problem
> which happens while running multiple graphics tests in parallel on
> Tegra30, i.e. by having multiple threads racing with each other in the
> Host1x's submission and completion code paths, performing IOVA mappings
> and unmappings in parallel.
> 
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
> 
> Changelog:
> 
> v2: - Now using mutex instead of spinlock.
> 
>     - The _locked postfix is replaced with the underscores prefix.
> 

Hello Thierry and Joerg!

Guys, are you okay with the v2 variant? Will be great if we could fix
the issue ASAP since it's quite unpleasant. Thanks in advance!