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iommu/tegra-smmu: Expand mutex protection range

Browse source 
This is used to protect potential race condition at use_count.
since probes of client drivers, calling attach_dev(), may run
concurrently.

Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
Tested-by: Dmitry Osipenko <digetx@gmail.com>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20201125101013.14953-3-nicoleotsuka@gmail.com
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Nicolin Chen 2020-11-25 02:10:10 -08:00 committed by Will Deacon
parent cf910f61af
commit d5f583bf86
1 changed files with 21 additions and 13 deletions
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34
drivers/iommu/tegra-smmu.c
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@ -256,26 +256,19 @@ static int tegra_smmu_alloc_asid(struct tegra_smmu *smmu, unsigned int *idp)
{
unsigned long id;
mutex_lock(&smmu->lock);
id = find_first_zero_bit(smmu->asids, smmu->soc->num_asids);
if (id >= smmu->soc->num_asids) {
mutex_unlock(&smmu->lock);
if (id >= smmu->soc->num_asids)
return -ENOSPC;
}
set_bit(id, smmu->asids);
*idp = id;
mutex_unlock(&smmu->lock);
return 0;
}
static void tegra_smmu_free_asid(struct tegra_smmu *smmu, unsigned int id)
{
mutex_lock(&smmu->lock);
clear_bit(id, smmu->asids);
mutex_unlock(&smmu->lock);
}
static bool tegra_smmu_capable(enum iommu_cap cap)
@ -420,17 +413,21 @@ static int tegra_smmu_as_prepare(struct tegra_smmu *smmu,
struct tegra_smmu_as *as)
{
u32 value;
int err;
int err = 0;
mutex_lock(&smmu->lock);
if (as->use_count > 0) {
as->use_count++;
return 0;
goto unlock;
}
as->pd_dma = dma_map_page(smmu->dev, as->pd, 0, SMMU_SIZE_PD,
DMA_TO_DEVICE);
if (dma_mapping_error(smmu->dev, as->pd_dma))
return -ENOMEM;
if (dma_mapping_error(smmu->dev, as->pd_dma)) {
err = -ENOMEM;
goto unlock;
}
/* We can't handle 64-bit DMA addresses */
if (!smmu_dma_addr_valid(smmu, as->pd_dma)) {
@ -453,24 +450,35 @@ static int tegra_smmu_as_prepare(struct tegra_smmu *smmu,
as->smmu = smmu;
as->use_count++;
mutex_unlock(&smmu->lock);
return 0;
err_unmap:
dma_unmap_page(smmu->dev, as->pd_dma, SMMU_SIZE_PD, DMA_TO_DEVICE);
unlock:
mutex_unlock(&smmu->lock);
return err;
}
static void tegra_smmu_as_unprepare(struct tegra_smmu *smmu,
struct tegra_smmu_as *as)
{
if (--as->use_count > 0)
mutex_lock(&smmu->lock);
if (--as->use_count > 0) {
mutex_unlock(&smmu->lock);
return;
}
tegra_smmu_free_asid(smmu, as->id);
dma_unmap_page(smmu->dev, as->pd_dma, SMMU_SIZE_PD, DMA_TO_DEVICE);
as->smmu = NULL;
mutex_unlock(&smmu->lock);
}
static int tegra_smmu_attach_dev(struct iommu_domain *domain,