[RFC PATCH 4/5] iommu/io-pgtable-arm: Implement arm_lpae_unmap_pages()
Robin Murphy
robin.murphy at arm.com
Thu Apr 1 18:19:32 BST 2021
On 2021-03-31 04:00, Isaac J. Manjarres wrote:
> Implement the unmap_pages() callback for the ARM LPAE io-pgtable
> format.
>
> Signed-off-by: Isaac J. Manjarres <isaacm at codeaurora.org>
> Suggested-by: Will Deacon <will at kernel.org>
> ---
> drivers/iommu/io-pgtable-arm.c | 114 +++++++++++++++++++++++++++------
> 1 file changed, 94 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
> index 87def58e79b5..6eccebf1744d 100644
> --- a/drivers/iommu/io-pgtable-arm.c
> +++ b/drivers/iommu/io-pgtable-arm.c
> @@ -248,10 +248,26 @@ static void __arm_lpae_set_pte(arm_lpae_iopte *ptep, arm_lpae_iopte pte,
> __arm_lpae_sync_pte(ptep, cfg);
> }
>
> +static void __arm_lpae_sync_ptes(arm_lpae_iopte *ptep, size_t num_ptes,
> + struct io_pgtable_cfg *cfg)
> +{
> + dma_sync_single_for_device(cfg->iommu_dev, __arm_lpae_dma_addr(ptep),
> + sizeof(*ptep) * num_ptes, DMA_TO_DEVICE);
> +}
> +
> +static void __arm_lpae_clear_ptes(arm_lpae_iopte *ptep, size_t num_ptes,
> + struct io_pgtable_cfg *cfg)
> +{
> + memset(ptep, 0, sizeof(*ptep) * num_ptes);
> +
> + if (!cfg->coherent_walk)
> + __arm_lpae_sync_ptes(ptep, num_ptes, cfg);
> +}
> +
It seesm like overkill to add separate functions - the existing ones
could easily just take an extra argument, like we do for the v7s format.
> static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data,
> struct iommu_iotlb_gather *gather,
> - unsigned long iova, size_t size, int lvl,
> - arm_lpae_iopte *ptep);
> + unsigned long iova, size_t size, size_t pgcount,
> + int lvl, arm_lpae_iopte *ptep);
>
> static void __arm_lpae_init_pte(struct arm_lpae_io_pgtable *data,
> phys_addr_t paddr, arm_lpae_iopte prot,
> @@ -289,7 +305,7 @@ static int arm_lpae_init_pte(struct arm_lpae_io_pgtable *data,
> size_t sz = ARM_LPAE_BLOCK_SIZE(lvl, data);
>
> tblp = ptep - ARM_LPAE_LVL_IDX(iova, lvl, data);
> - if (__arm_lpae_unmap(data, NULL, iova, sz, lvl, tblp) != sz) {
> + if (__arm_lpae_unmap(data, NULL, iova, sz, 1, lvl, tblp) != sz) {
> WARN_ON(1);
> return -EINVAL;
> }
> @@ -516,14 +532,14 @@ static size_t arm_lpae_split_blk_unmap(struct arm_lpae_io_pgtable *data,
> struct iommu_iotlb_gather *gather,
> unsigned long iova, size_t size,
> arm_lpae_iopte blk_pte, int lvl,
> - arm_lpae_iopte *ptep)
> + arm_lpae_iopte *ptep, size_t pgcount)
> {
> struct io_pgtable_cfg *cfg = &data->iop.cfg;
> arm_lpae_iopte pte, *tablep;
> phys_addr_t blk_paddr;
> size_t tablesz = ARM_LPAE_GRANULE(data);
> size_t split_sz = ARM_LPAE_BLOCK_SIZE(lvl, data);
> - int i, unmap_idx = -1;
> + int i, unmap_idx_start = -1;
>
> if (WARN_ON(lvl == ARM_LPAE_MAX_LEVELS))
> return 0;
> @@ -533,14 +549,14 @@ static size_t arm_lpae_split_blk_unmap(struct arm_lpae_io_pgtable *data,
> return 0; /* Bytes unmapped */
>
> if (size == split_sz)
> - unmap_idx = ARM_LPAE_LVL_IDX(iova, lvl, data);
> + unmap_idx_start = ARM_LPAE_LVL_IDX(iova, lvl, data);
>
> blk_paddr = iopte_to_paddr(blk_pte, data);
> pte = iopte_prot(blk_pte);
>
> for (i = 0; i < tablesz / sizeof(pte); i++, blk_paddr += split_sz) {
> /* Unmap! */
> - if (i == unmap_idx)
> + if (i >= unmap_idx_start && i < (unmap_idx_start + pgcount))
> continue;
>
> __arm_lpae_init_pte(data, blk_paddr, pte, lvl, &tablep[i]);
> @@ -558,20 +574,24 @@ static size_t arm_lpae_split_blk_unmap(struct arm_lpae_io_pgtable *data,
> return 0;
>
> tablep = iopte_deref(pte, data);
> - } else if (unmap_idx >= 0) {
> - io_pgtable_tlb_add_page(&data->iop, gather, iova, size);
> - return size;
> + } else if (unmap_idx_start >= 0) {
> + for (i = 0; i < pgcount; i++) {
> + io_pgtable_tlb_add_page(&data->iop, gather, iova, size);
> + iova += size;
> + }
> + return pgcount * size;
> }
>
> - return __arm_lpae_unmap(data, gather, iova, size, lvl, tablep);
> + return __arm_lpae_unmap(data, gather, iova, size, pgcount, lvl, tablep);
> }
>
> static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data,
> struct iommu_iotlb_gather *gather,
> - unsigned long iova, size_t size, int lvl,
> - arm_lpae_iopte *ptep)
> + unsigned long iova, size_t size, size_t pgcount,
> + int lvl, arm_lpae_iopte *ptep)
> {
> arm_lpae_iopte pte;
> + size_t i;
> struct io_pgtable *iop = &data->iop;
>
> /* Something went horribly wrong and we ran out of page table */
> @@ -585,11 +605,11 @@ static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data,
>
> /* If the size matches this level, we're in the right place */
> if (size == ARM_LPAE_BLOCK_SIZE(lvl, data)) {
> - __arm_lpae_set_pte(ptep, 0, &iop->cfg);
> + __arm_lpae_clear_ptes(ptep, pgcount, &iop->cfg);
>
> if (!iopte_leaf(pte, lvl, iop->fmt)) {
> /* Also flush any partial walks */
> - io_pgtable_tlb_flush_walk(iop, iova, size,
> + io_pgtable_tlb_flush_walk(iop, iova, pgcount * size,
> ARM_LPAE_GRANULE(data));
> ptep = iopte_deref(pte, data);
> __arm_lpae_free_pgtable(data, lvl + 1, ptep);
> @@ -601,22 +621,25 @@ static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data,
> */
> smp_wmb();
> } else {
> - io_pgtable_tlb_add_page(iop, gather, iova, size);
> + for (i = 0; i < pgcount; i++) {
> + io_pgtable_tlb_add_page(iop, gather, iova, size);
> + iova += size;
> + }
> }
>
> - return size;
> + return pgcount * size;
> } else if (iopte_leaf(pte, lvl, iop->fmt)) {
> /*
> * Insert a table at the next level to map the old region,
> * minus the part we want to unmap
> */
> return arm_lpae_split_blk_unmap(data, gather, iova, size, pte,
> - lvl + 1, ptep);
> + lvl + 1, ptep, pgcount);
> }
>
> /* Keep on walkin' */
> ptep = iopte_deref(pte, data);
> - return __arm_lpae_unmap(data, gather, iova, size, lvl + 1, ptep);
> + return __arm_lpae_unmap(data, gather, iova, size, pgcount, lvl + 1, ptep);
> }
>
> static size_t arm_lpae_unmap(struct io_pgtable_ops *ops, unsigned long iova,
> @@ -635,7 +658,57 @@ static size_t arm_lpae_unmap(struct io_pgtable_ops *ops, unsigned long iova,
> if (WARN_ON(iaext))
> return 0;
>
> - return __arm_lpae_unmap(data, gather, iova, size, data->start_level, ptep);
> + return __arm_lpae_unmap(data, gather, iova, size, 1, data->start_level, ptep);
> +}
> +
> +static size_t arm_lpae_unmap_pages(struct io_pgtable_ops *ops, unsigned long iova,
> + size_t pgsize, size_t pgcount,
> + struct iommu_iotlb_gather *gather)
> +{
> + struct arm_lpae_io_pgtable *data = io_pgtable_ops_to_data(ops);
> + struct io_pgtable_cfg *cfg = &data->iop.cfg;
> + arm_lpae_iopte *ptep = data->pgd;
> + long iaext = (s64)iova >> cfg->ias;
> + size_t unmapped = 0, unmapped_page;
> + int last_lvl = data->start_level;
> + size_t table_size, pages, tbl_offset, max_entries;
> +
> + if (WARN_ON(!pgsize || (pgsize & cfg->pgsize_bitmap) != pgsize || !pgcount))
> + return 0;
> +
> + if (cfg->quirks & IO_PGTABLE_QUIRK_ARM_TTBR1)
> + iaext = ~iaext;
> + if (WARN_ON(iaext))
> + return 0;
> +
> + /*
> + * Calculating the page table size here helps avoid situations where
> + * a page range that is being unmapped may be mapped at the same level
> + * but not mapped by the same tables. Allowing such a scenario to
> + * occur can complicate the logic in arm_lpae_split_blk_unmap().
> + */
> + while (ARM_LPAE_BLOCK_SIZE(last_lvl, data) != pgsize)
> + last_lvl++;
> +
> + table_size = last_lvl == data->start_level ? ARM_LPAE_PGD_SIZE(data) :
> + ARM_LPAE_GRANULE(data);
> + max_entries = table_size / sizeof(*ptep);
I'm really struggling to understand what's going on here :/
When would table_size ever not be equal to page_size? (In a way that
matters - manipulating top-level block entries in a concatenated stage 2
table is hardly going to be common enough to deserve specific optimisation)
> + while (pgcount) {
> + tbl_offset = ARM_LPAE_LVL_IDX(iova, last_lvl, data);
> + pages = min_t(size_t, pgcount, max_entries - tbl_offset);
> + unmapped_page = __arm_lpae_unmap(data, gather, iova, pgsize,
> + pages, data->start_level,
> + ptep);
This again seems less efficient than it deserves to be - iterating
within __arm_lpae_unmap() itself would seem to make more sense than
recursing all the way in and out multiple times per operation.
> + if (!unmapped_page)
> + break;
> +
> + unmapped += unmapped_page;
> + iova += unmapped_page;
> + pgcount -= pages;
> + }
> +
> + return unmapped;
> }
>
> static phys_addr_t arm_lpae_iova_to_phys(struct io_pgtable_ops *ops,
> @@ -751,6 +824,7 @@ arm_lpae_alloc_pgtable(struct io_pgtable_cfg *cfg)
> data->iop.ops = (struct io_pgtable_ops) {
> .map = arm_lpae_map,
> .unmap = arm_lpae_unmap,
> + .unmap_pages = arm_lpae_unmap_pages,
Why would we need to keep the old callback and have a bunch of
duplicated code? Even fully converting all the users isn't _that_
involved, but having them just call .unmap_pages with n=1 is even less so.
Robin.
> .iova_to_phys = arm_lpae_iova_to_phys,
> };
>
>
More information about the linux-arm-kernel
mailing list