Commit d5f583bf authored by Nicolin Chen's avatar Nicolin Chen Committed by Will Deacon
Browse files

iommu/tegra-smmu: Expand mutex protection range 



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: default avatarNicolin Chen <nicoleotsuka@gmail.com>
Tested-by: default avatarDmitry Osipenko <digetx@gmail.com>
Reviewed-by: default avatarDmitry Osipenko <digetx@gmail.com>
Acked-by: default avatarThierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20201125101013.14953-3-nicoleotsuka@gmail.com


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent cf910f61

drivers/iommu/tegra-smmu.c

+21 −13
Original line number Diff line number Diff line
@@ -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,