linux-kernel - Re: [PATCH v3 1/6] iommu/core: split mapping to page sizes as supported by the hardware

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Message-ID: <CAHQjnOPcetkp-XX0x4HQsR+iYN1SaCAhuBEE2nVTdhssFpUmJQ@mail.gmail.com>
Date:	Tue, 11 Oct 2011 23:59:53 +0900
From:	KyongHo Cho <pullip.cho@...sung.com>
To:	Ohad Ben-Cohen <ohad@...ery.com>
Cc:	"Roedel, Joerg" <Joerg.Roedel@....com>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	David Woodhouse <dwmw2@...radead.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	David Brown <davidb@...eaurora.org>,
	Arnd Bergmann <arnd@...db.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Stepan Moskovchenko <stepanm@...eaurora.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	Hiroshi Doyu <hdoyu@...dia.com>,
	Kukjin Kim <kgene.kim@...sung.com>
Subject: Re: [PATCH v3 1/6] iommu/core: split mapping to page sizes as
 supported by the hardware

On Tue, Oct 11, 2011 at 7:49 AM, Ohad Ben-Cohen <ohad@...ery.com> wrote:
>  int iommu_map(struct iommu_domain *domain, unsigned long iova,
> -             phys_addr_t paddr, int gfp_order, int prot)
> +             phys_addr_t paddr, int size, int prot)
>  {
Even though it is not realistic that size becomes larger than 1 <<
((sizeof(int) * 8) - 1),
I think the type of size should be size_t.

> -       size_t size;
> +       unsigned long orig_iova = iova;
> +       int ret = 0, orig_size = size;
>
>        if (unlikely(domain->ops->map == NULL))
>                return -ENODEV;
>
> -       size         = PAGE_SIZE << gfp_order;
> +       /*
> +        * 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, domain->ops->min_pagesz)) {
> +               pr_err("unaligned: iova 0x%lx pa 0x%lx size 0x%x min_pagesz "
> +                       "0x%x\n", iova, (unsigned long)paddr,
> +                       size, domain->ops->min_pagesz);
> +               return -EINVAL;
> +       }
> +
> +       pr_debug("map: iova 0x%lx pa 0x%lx size 0x%x\n", iova,
> +                               (unsigned long)paddr, size);
> +
> +       while (size) {
> +               unsigned long pgsize, addr_merge = iova | paddr;
> +               unsigned int pgsize_idx;
> +
> +               /* Max page size that still fits into 'size' */
> +               pgsize_idx = __fls(size);
> +
> +               /* need to consider alignment requirements ? */
> +               if (likely(addr_merge)) {
> +                       /* Max page size allowed by both iova and paddr */
> +                       unsigned int align_pgsize_idx = __ffs(addr_merge);
> +
> +                       pgsize_idx = min(pgsize_idx, align_pgsize_idx);
> +               }
> +
> +               /* build a mask of acceptable page sizes */
> +               pgsize = (1UL << (pgsize_idx + 1)) - 1;
> +
> +               /* throw away page sizes not supported by the hardware */
> +               pgsize &= domain->ops->pgsize_bitmap;
> +
> +               /* make sure we're still sane */
> +               BUG_ON(!pgsize);
>
> -       BUG_ON(!IS_ALIGNED(iova | paddr, size));
> +               /* pick the biggest page */
> +               pgsize_idx = __fls(pgsize);
> +               pgsize = 1UL << pgsize_idx;
>
> -       return domain->ops->map(domain, iova, paddr, gfp_order, prot);
> +               /* convert index to page order */
> +               pgsize_idx -= PAGE_SHIFT;
> +
> +               pr_debug("mapping: iova 0x%lx pa 0x%lx order %u\n", iova,
> +                                       (unsigned long)paddr, pgsize_idx);
> +
> +               ret = domain->ops->map(domain, iova, paddr, pgsize_idx, prot);
> +               if (ret)
> +                       break;
> +
> +               iova += pgsize;
> +               paddr += pgsize;
> +               size -= pgsize;
> +       }
> +
> +       /* unroll mapping in case something went wrong */
> +       if (ret)
> +               iommu_unmap(domain, orig_iova, orig_size);
> +
domain->ops->map() might return error because a mapping already exists
in the range from iova until iova + size.
Thus, it should be
iommu_unmap(domain, orig_iova, orig_size - size)

Regards,

KyongHo
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