alloc_pdir() is called from smmu_iommu_domain_init() with spin_lock
held. memory allocations in alloc_pdir() had to be atomic. Instead of
converting into atomic allocation, this patch once releases a lock,
does the allocation, holds the lock again and then sees if it's raced
or not in order to avoid introducing mutex and preallocation.
Signed-off-by: Hiroshi DOYU <hdoyu@xxxxxxxxxx>
Reported-by: Chris Wright <chrisw@xxxxxxxxxxxx>
Cc: Chris Wright <chrisw@xxxxxxxxxxxx>
Acked-by: Stephen Warren <swarren@xxxxxxxxxxxxx>
---
drivers/iommu/tegra-smmu.c | 77 +++++++++++++++++++++++++------------------
1 files changed, 45 insertions(+), 32 deletions(-)
diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c
index 532c8a4..dbba94c 100644
--- a/drivers/iommu/tegra-smmu.c
+++ b/drivers/iommu/tegra-smmu.c
@@ -539,28 +539,39 @@ static inline void put_signature(struct smmu_as *as,
/*
* Caller must lock/unlock as
*/
-static int alloc_pdir(struct smmu_as *as)
+static int alloc_pdir(struct smmu_as *as, unsigned long *flags)
{
unsigned long *pdir;
- int pdn;
+ int pdn, err = 0;
u32 val;
struct smmu_device *smmu = as->smmu;
+ struct page *page;
+ unsigned int *cnt;
- as->pte_count = devm_kzalloc(smmu->dev,
- sizeof(as->pte_count[0]) * SMMU_PDIR_COUNT, GFP_KERNEL);
- if (!as->pte_count) {
- dev_err(smmu->dev,
- "failed to allocate smmu_device PTE cunters\n");
- return -ENOMEM;
+ /*
+ * do the allocation outside the as lock
+ */
+ spin_unlock_irqrestore(&as->lock, *flags);
+ cnt = devm_kzalloc(smmu->dev,
+ sizeof(cnt[0]) * SMMU_PDIR_COUNT, GFP_KERNEL);
+ page = alloc_page(GFP_KERNEL | __GFP_DMA);
+ spin_lock_irqsave(&as->lock, *flags);
+
+ if (as->pdir_page) {
+ /* We raced, free the redundant */
+ err = -EAGAIN;
+ goto err_out;
}
- as->pdir_page = alloc_page(GFP_KERNEL | __GFP_DMA);
- if (!as->pdir_page) {
- dev_err(smmu->dev,
- "failed to allocate smmu_device page directory\n");
- devm_kfree(smmu->dev, as->pte_count);
- as->pte_count = NULL;
- return -ENOMEM;
+
+ if (!page || !cnt) {
+ dev_err(smmu->dev, "failed to allocate at %s\n", __func__);
+ err = -ENOMEM;
+ goto err_out;
}
+
+ as->pdir_page = page;
+ as->pte_count = cnt;
+
SetPageReserved(as->pdir_page);
pdir = page_address(as->pdir_page);
@@ -577,6 +588,12 @@ static int alloc_pdir(struct smmu_as *as)
FLUSH_SMMU_REGS(as->smmu);
return 0;
+
+err_out:
+ devm_kfree(smmu->dev, cnt);
+ if (page)
+ __free_page(page);
+ return err;
}
static void __smmu_iommu_unmap(struct smmu_as *as, dma_addr_t iova)
@@ -768,29 +785,29 @@ out:
static int smmu_iommu_domain_init(struct iommu_domain *domain)
{
- int i;
+ int i, err = -ENODEV;
unsigned long flags;
struct smmu_as *as;
struct smmu_device *smmu = smmu_handle;
/* Look for a free AS with lock held */
for (i = 0; i < smmu->num_as; i++) {
- struct smmu_as *tmp = &smmu->as[i];
-
- spin_lock_irqsave(&tmp->lock, flags);
- if (!tmp->pdir_page) {
- as = tmp;
- goto found;
+ as = &smmu->as[i];
+ spin_lock_irqsave(&as->lock, flags);
+ if (!as->pdir_page) {
+ err = alloc_pdir(as, &flags);
+ if (!err)
+ goto found;
}
- spin_unlock_irqrestore(&tmp->lock, flags);
+ spin_unlock_irqrestore(&as->lock, flags);
+ if (err != -EAGAIN)
+ break;
}
- dev_err(smmu->dev, "no free AS\n");
- return -ENODEV;
+ if (i == smmu->num_as)
+ dev_err(smmu->dev, "no free AS\n");
+ return err;
found:
- if (alloc_pdir(as) < 0)
- goto err_alloc_pdir;
-
spin_lock(&smmu->lock);
/* Update PDIR register */
@@ -806,10 +823,6 @@ found:
dev_dbg(smmu->dev, "smmu_as@%p\n", as);
return 0;
-
-err_alloc_pdir:
- spin_unlock_irqrestore(&as->lock, flags);
- return -ENODEV;
}
static void smmu_iommu_domain_destroy(struct iommu_domain *domain)
--
1.7.5.4
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