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SubjectRe: [PATCH v3 1/6] iommu/core: split mapping to page sizes as supported by the hardware
On Fri, Sep 16, 2011 at 01:51:41PM -0400, Ohad Ben-Cohen wrote:
> drivers/iommu/iommu.c | 158 +++++++++++++++++++++++++++++++++++++++++---
> drivers/iommu/omap-iovmm.c | 12 +---
> include/linux/iommu.h | 6 +-
> virt/kvm/iommu.c | 4 +-
> 4 files changed, 157 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index c68ff29..7c01c8c 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -16,6 +16,8 @@
> * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
> */
>
> +#define pr_fmt(fmt) "%s: " fmt, __func__
> +
> #include <linux/kernel.h>
> #include <linux/bug.h>
> #include <linux/types.h>
> @@ -23,15 +25,73 @@
> #include <linux/slab.h>
> #include <linux/errno.h>
> #include <linux/iommu.h>
> +#include <linux/bitmap.h>
>
> static struct iommu_ops *iommu_ops;
>
> +/* bitmap of supported page sizes */
> +static unsigned long *iommu_pgsize_bitmap;
> +
> +/* number of bits used to represent the supported pages */
> +static unsigned int iommu_nr_page_bits;
> +
> +/* size of the smallest supported page (in bytes) */
> +static unsigned int iommu_min_pagesz;
> +
> +/* bit number of the smallest supported page */
> +static unsigned int iommu_min_page_idx;
> +
> +/**
> + * register_iommu() - register an IOMMU hardware
> + * @ops: iommu handlers
> + * @pgsize_bitmap: bitmap of page sizes supported by the hardware
> + * @nr_page_bits: size of @pgsize_bitmap (in bits)
> + *
> + * Note: this is a temporary function, which will be removed once
> + * all IOMMU drivers are converted. The only reason it exists is to
> + * allow splitting the pgsizes changes to several patches in order to ease
> + * the review.
> + */
> +void register_iommu_pgsize(struct iommu_ops *ops, unsigned long *pgsize_bitmap,
> + unsigned int nr_page_bits)

I think a plain unsigned long value is sufficient to encode the
supported page-sizes. No need to use a full bitmap.

> int iommu_map(struct iommu_domain *domain, unsigned long iova,
> - phys_addr_t paddr, int gfp_order, int prot)
> + phys_addr_t paddr, size_t size, int prot)
> {
> - size_t size;
> + int ret = 0;
> +
> + /*
> + * both the virtual address and the physical one, as well as
> + * the size of the mapping, must be aligned (at least) to the
> + * size of the smallest page supported by the hardware
> + */
> + if (!IS_ALIGNED(iova | paddr | size, iommu_min_pagesz)) {
> + pr_err("unaligned: iova 0x%lx pa 0x%lx size 0x%lx min_pagesz "
> + "0x%x\n", iova, (unsigned long)paddr,
> + (unsigned long)size, iommu_min_pagesz);
> + return -EINVAL;
> + }
> +
> + pr_debug("map: iova 0x%lx pa 0x%lx size 0x%lx\n", iova,
> + (unsigned long)paddr, (unsigned long)size);
> +
> + while (size) {
> + unsigned long pgsize = iommu_min_pagesz;
> + unsigned long idx = iommu_min_page_idx;
> + unsigned long addr_merge = iova | paddr;
> + int order;
> +
> + /* find the max page size with which iova, paddr are aligned */
> + for (;;) {
> + unsigned long try_pgsize;
> +
> + idx = find_next_bit(iommu_pgsize_bitmap,
> + iommu_nr_page_bits, idx + 1);
> +
> + /* no more pages to check ? */
> + if (idx >= iommu_nr_page_bits)
> + break;
> +
> + try_pgsize = 1 << idx;
>
> - size = 0x1000UL << gfp_order;
> + /* page too big ? addresses not aligned ? */
> + if (size < try_pgsize ||
> + !IS_ALIGNED(addr_merge, try_pgsize))
> + break;
>
> - BUG_ON(!IS_ALIGNED(iova | paddr, size));
> + pgsize = try_pgsize;
> + }

With an unsigned long you can use plain and fast bit_ops instead of the
full bitmap functions.

>
> - return iommu_ops->map(domain, iova, paddr, gfp_order, prot);
> + order = get_order(pgsize);
> +
> + pr_debug("mapping: iova 0x%lx pa 0x%lx order %d\n", iova,
> + (unsigned long)paddr, order);
> +
> + ret = iommu_ops->map(domain, iova, paddr, order, prot);
> + if (ret)
> + break;
> +
> + size -= pgsize;
> + iova += pgsize;
> + paddr += pgsize;
> + }
> +
> + return ret;
> }
> EXPORT_SYMBOL_GPL(iommu_map);
>

--
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