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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);
    >

    --
    AMD Operating System Research Center

    Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach
    General Managers: Alberto Bozzo, Andrew Bowd
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