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iommu/tegra-smmu: Fix page table lookup in unmap/iova_to_phys methods

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Fix the page table lookup in the unmap and iova_to_phys methods.
Neither of these methods should allocate a page table; a missing page
table should be treated the same as no mapping present.

More importantly, using as_get_pte() for an IOVA corresponding with a
non-present page table entry increments the use-count for the page
table, on the assumption that the caller of as_get_pte() is going to
setup a mapping.  This is an incorrect assumption.

Fix both of these bugs by providing a separate helper which only looks
up the page table, but never allocates it.  This is akin to pte_offset()
for CPU page tables.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Thierry Reding <treding@nvidia.com>
This commit is contained in:
Russell King 2015-07-27 13:29:21 +01:00 committed by Thierry Reding
parent 34d35f8cbe
commit 0b42c7c113
1 changed files with 34 additions and 9 deletions
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43
drivers/iommu/tegra-smmu.c
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@ -475,12 +475,36 @@ static void tegra_smmu_detach_dev(struct iommu_domain *domain, struct device *de
}
}
static u32 *tegra_smmu_pte_offset(struct page *pt_page, unsigned long iova)
{
u32 *pt = page_address(pt_page);
return pt + iova_pt_index(iova);
}
static u32 *tegra_smmu_pte_lookup(struct tegra_smmu_as *as, unsigned long iova,
struct page **pagep)
{
unsigned int pd_index = iova_pd_index(iova);
struct page *pt_page;
u32 *pd;
pd = page_address(as->pd);
if (!pd[pd_index])
return NULL;
pt_page = pfn_to_page(pd[pd_index] & as->smmu->pfn_mask);
*pagep = pt_page;
return tegra_smmu_pte_offset(pt_page, iova);
}
static u32 *as_get_pte(struct tegra_smmu_as *as, dma_addr_t iova,
struct page **pagep)
{
u32 *pd = page_address(as->pd), *pt, *count;
unsigned int pde = iova_pd_index(iova);
unsigned int pte = iova_pt_index(iova);
struct tegra_smmu *smmu = as->smmu;
struct page *page;
unsigned int i;
@ -506,17 +530,18 @@ static u32 *as_get_pte(struct tegra_smmu_as *as, dma_addr_t iova,
smmu_flush(smmu);
} else {
page = pfn_to_page(pd[pde] & smmu->pfn_mask);
pt = page_address(page);
}
*pagep = page;
pt = page_address(page);
/* Keep track of entries in this page table. */
count = page_address(as->count);
if (pt[pte] == 0)
if (pt[iova_pt_index(iova)] == 0)
count[pde]++;
return &pt[pte];
return tegra_smmu_pte_offset(page, iova);
}
static void tegra_smmu_pte_put_use(struct tegra_smmu_as *as, unsigned long iova)
@ -586,14 +611,14 @@ static size_t tegra_smmu_unmap(struct iommu_domain *domain, unsigned long iova,
size_t size)
{
struct tegra_smmu_as *as = to_smmu_as(domain);
struct page *page;
struct page *pte_page;
u32 *pte;
pte = as_get_pte(as, iova, &page);
pte = tegra_smmu_pte_lookup(as, iova, &pte_page);
if (!pte || !*pte)
return 0;
tegra_smmu_set_pte(as, iova, pte, page, 0);
tegra_smmu_set_pte(as, iova, pte, pte_page, 0);
tegra_smmu_pte_put_use(as, iova);
return size;
@ -603,11 +628,11 @@ static phys_addr_t tegra_smmu_iova_to_phys(struct iommu_domain *domain,
dma_addr_t iova)
{
struct tegra_smmu_as *as = to_smmu_as(domain);
struct page *page;
struct page *pte_page;
unsigned long pfn;
u32 *pte;
pte = as_get_pte(as, iova, &page);
pte = tegra_smmu_pte_lookup(as, iova, &pte_page);
if (!pte || !*pte)
return 0;