[PATCH 02/19] iommu/tegra: Do not use struct page as the handle for pts
Robin Murphy
robin.murphy at arm.com
Wed Feb 5 11:28:37 PST 2025
On 2025-02-04 6:34 pm, Jason Gunthorpe wrote:
> Instead use the virtual address and dma_map_single() like as->pd
> uses. Introduce a small struct tegra_pt instead of void * to have some
> clarity what is using this API and add compile safety during the
> conversion.
Hmm, I'm not sure it's all that clear to have a major discrepancy
between how different levels of pagetable are referenced - I'd say
either use an explicit type for both, or just rework this as a u32**
along the same lines as the current patch #1.
> Signed-off-by: Jason Gunthorpe <jgg at nvidia.com>
> ---
> drivers/iommu/tegra-smmu.c | 68 ++++++++++++++++++++------------------
> 1 file changed, 36 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c
> index 717bcd3b8de7dc..1e85141c80548d 100644
> --- a/drivers/iommu/tegra-smmu.c
> +++ b/drivers/iommu/tegra-smmu.c
> @@ -51,13 +51,15 @@ struct tegra_smmu {
> struct iommu_device iommu; /* IOMMU Core code handle */
> };
>
> +struct tegra_pt;
> +
> struct tegra_smmu_as {
> struct iommu_domain domain;
> struct tegra_smmu *smmu;
> unsigned int use_count;
> spinlock_t lock;
> u32 *count;
> - struct page **pts;
> + struct tegra_pt **pts;
> u32 *pd;
> dma_addr_t pd_dma;
> unsigned id;
> @@ -155,6 +157,10 @@ static inline u32 smmu_readl(struct tegra_smmu *smmu, unsigned long offset)
> #define SMMU_PDE_ATTR (SMMU_PDE_READABLE | SMMU_PDE_WRITABLE | \
> SMMU_PDE_NONSECURE)
>
> +struct tegra_pt {
> + u32 val[SMMU_NUM_PTE];
> +};
> +
> static unsigned int iova_pd_index(unsigned long iova)
> {
> return (iova >> SMMU_PDE_SHIFT) & (SMMU_NUM_PDE - 1);
> @@ -564,11 +570,9 @@ static void tegra_smmu_set_pde(struct tegra_smmu_as *as, unsigned long iova,
> smmu_flush(smmu);
> }
>
> -static u32 *tegra_smmu_pte_offset(struct page *pt_page, unsigned long iova)
> +static u32 *tegra_smmu_pte_offset(struct tegra_pt *pt, unsigned long iova)
> {
> - u32 *pt = page_address(pt_page);
> -
> - return pt + iova_pt_index(iova);
> + return &pt->val[iova_pt_index(iova)];
> }
>
> static u32 *tegra_smmu_pte_lookup(struct tegra_smmu_as *as, unsigned long iova,
> @@ -576,19 +580,19 @@ static u32 *tegra_smmu_pte_lookup(struct tegra_smmu_as *as, unsigned long iova,
> {
> unsigned int pd_index = iova_pd_index(iova);
> struct tegra_smmu *smmu = as->smmu;
> - struct page *pt_page;
> + struct tegra_pt *pt;
>
> - pt_page = as->pts[pd_index];
> - if (!pt_page)
> + pt = as->pts[pd_index];
> + if (!pt)
> return NULL;
>
> *dmap = smmu_pde_to_dma(smmu, as->pd[pd_index]);
>
> - return tegra_smmu_pte_offset(pt_page, iova);
> + return tegra_smmu_pte_offset(pt, iova);
> }
>
> static u32 *as_get_pte(struct tegra_smmu_as *as, dma_addr_t iova,
> - dma_addr_t *dmap, struct page *page)
> + dma_addr_t *dmap, struct tegra_pt *pt)
> {
> unsigned int pde = iova_pd_index(iova);
> struct tegra_smmu *smmu = as->smmu;
> @@ -596,21 +600,21 @@ static u32 *as_get_pte(struct tegra_smmu_as *as, dma_addr_t iova,
> if (!as->pts[pde]) {
> dma_addr_t dma;
>
> - dma = dma_map_page(smmu->dev, page, 0, SMMU_SIZE_PT,
> - DMA_TO_DEVICE);
> + dma = dma_map_single(smmu->dev, pt, SMMU_SIZE_PD,
SMMU_SIZE_PT (yeah they're numerically the same, but still...)
> + DMA_TO_DEVICE);
> if (dma_mapping_error(smmu->dev, dma)) {
> - __iommu_free_pages(page, 0);
> + iommu_free_page(pt);
> return NULL;
> }
>
> if (!smmu_dma_addr_valid(smmu, dma)) {
> dma_unmap_page(smmu->dev, dma, SMMU_SIZE_PT,
> DMA_TO_DEVICE);
All the unmaps should be converted to _single as well (and in patch #1)
- the APIs are not officially interchangeable.
Thanks,
Robin.
> - __iommu_free_pages(page, 0);
> + iommu_free_page(pt);
> return NULL;
> }
>
> - as->pts[pde] = page;
> + as->pts[pde] = pt;
>
> tegra_smmu_set_pde(as, iova, SMMU_MK_PDE(dma, SMMU_PDE_ATTR |
> SMMU_PDE_NEXT));
> @@ -633,7 +637,7 @@ static void tegra_smmu_pte_get_use(struct tegra_smmu_as *as, unsigned long iova)
> static void tegra_smmu_pte_put_use(struct tegra_smmu_as *as, unsigned long iova)
> {
> unsigned int pde = iova_pd_index(iova);
> - struct page *page = as->pts[pde];
> + struct tegra_pt *pt = as->pts[pde];
>
> /*
> * When no entries in this page table are used anymore, return the
> @@ -646,7 +650,7 @@ static void tegra_smmu_pte_put_use(struct tegra_smmu_as *as, unsigned long iova)
> tegra_smmu_set_pde(as, iova, 0);
>
> dma_unmap_page(smmu->dev, pte_dma, SMMU_SIZE_PT, DMA_TO_DEVICE);
> - __iommu_free_pages(page, 0);
> + iommu_free_page(pt);
> as->pts[pde] = NULL;
> }
> }
> @@ -666,16 +670,16 @@ static void tegra_smmu_set_pte(struct tegra_smmu_as *as, unsigned long iova,
> smmu_flush(smmu);
> }
>
> -static struct page *as_get_pde_page(struct tegra_smmu_as *as,
> - unsigned long iova, gfp_t gfp,
> - unsigned long *flags)
> +static struct tegra_pt *as_get_pde_page(struct tegra_smmu_as *as,
> + unsigned long iova, gfp_t gfp,
> + unsigned long *flags)
> {
> unsigned int pde = iova_pd_index(iova);
> - struct page *page = as->pts[pde];
> + struct tegra_pt *pt = as->pts[pde];
>
> /* at first check whether allocation needs to be done at all */
> - if (page)
> - return page;
> + if (pt)
> + return pt;
>
> /*
> * In order to prevent exhaustion of the atomic memory pool, we
> @@ -685,7 +689,7 @@ static struct page *as_get_pde_page(struct tegra_smmu_as *as,
> if (gfpflags_allow_blocking(gfp))
> spin_unlock_irqrestore(&as->lock, *flags);
>
> - page = __iommu_alloc_pages(gfp | __GFP_DMA, 0);
> + pt = iommu_alloc_page(gfp | __GFP_DMA);
>
> if (gfpflags_allow_blocking(gfp))
> spin_lock_irqsave(&as->lock, *flags);
> @@ -696,13 +700,13 @@ static struct page *as_get_pde_page(struct tegra_smmu_as *as,
> * if allocation succeeded and the allocation failure isn't fatal.
> */
> if (as->pts[pde]) {
> - if (page)
> - __iommu_free_pages(page, 0);
> + if (pt)
> + iommu_free_page(pt);
>
> - page = as->pts[pde];
> + pt = as->pts[pde];
> }
>
> - return page;
> + return pt;
> }
>
> static int
> @@ -712,15 +716,15 @@ __tegra_smmu_map(struct iommu_domain *domain, unsigned long iova,
> {
> struct tegra_smmu_as *as = to_smmu_as(domain);
> dma_addr_t pte_dma;
> - struct page *page;
> + struct tegra_pt *pt;
> u32 pte_attrs;
> u32 *pte;
>
> - page = as_get_pde_page(as, iova, gfp, flags);
> - if (!page)
> + pt = as_get_pde_page(as, iova, gfp, flags);
> + if (!pt)
> return -ENOMEM;
>
> - pte = as_get_pte(as, iova, &pte_dma, page);
> + pte = as_get_pte(as, iova, &pte_dma, pt);
> if (!pte)
> return -ENOMEM;
>
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