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    Subject[PATCH 08/11] drm/i915: use vmap in i915_gem_object_map
    Date
    i915_gem_object_map implements fairly low-level vmap functionality in
    a driver. Split it into two helpers, one for remapping kernel memory
    which can use vmap, and one for I/O memory that uses vmap_pfn.

    The only practical difference is that alloc_vm_area prefeaults the
    vmalloc area PTEs, which doesn't seem to be required here for the
    kernel memory case (and could be added to vmap using a flag if actually
    required).

    Signed-off-by: Christoph Hellwig <hch@lst.de>
    ---
    drivers/gpu/drm/i915/Kconfig | 1 +
    drivers/gpu/drm/i915/gem/i915_gem_pages.c | 126 ++++++++++------------
    2 files changed, 59 insertions(+), 68 deletions(-)

    diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig
    index 9afa5c4a6bf006..1e1cb245fca778 100644
    --- a/drivers/gpu/drm/i915/Kconfig
    +++ b/drivers/gpu/drm/i915/Kconfig
    @@ -25,6 +25,7 @@ config DRM_I915
    select CRC32
    select SND_HDA_I915 if SND_HDA_CORE
    select CEC_CORE if CEC_NOTIFIER
    + select VMAP_PFN
    help
    Choose this option if you have a system that has "Intel Graphics
    Media Accelerator" or "HD Graphics" integrated graphics,
    diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
    index 6550c0bc824ea2..b519417667eb4b 100644
    --- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
    +++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
    @@ -232,34 +232,21 @@ int __i915_gem_object_put_pages(struct drm_i915_gem_object *obj)
    return err;
    }

    -static inline pte_t iomap_pte(resource_size_t base,
    - dma_addr_t offset,
    - pgprot_t prot)
    -{
    - return pte_mkspecial(pfn_pte((base + offset) >> PAGE_SHIFT, prot));
    -}
    -
    /* The 'mapping' part of i915_gem_object_pin_map() below */
    -static void *i915_gem_object_map(struct drm_i915_gem_object *obj,
    - enum i915_map_type type)
    +static void *i915_gem_object_map_page(struct drm_i915_gem_object *obj,
    + enum i915_map_type type)
    {
    - unsigned long n_pte = obj->base.size >> PAGE_SHIFT;
    - struct sg_table *sgt = obj->mm.pages;
    - pte_t *stack[32], **mem;
    - struct vm_struct *area;
    + unsigned long n_pages = obj->base.size >> PAGE_SHIFT, i;
    + struct page *stack[32], **pages = stack, *page;
    + struct sgt_iter iter;
    pgprot_t pgprot;
    + void *vaddr;

    - if (!i915_gem_object_has_struct_page(obj) && type != I915_MAP_WC)
    - return NULL;
    -
    - if (GEM_WARN_ON(type == I915_MAP_WC &&
    - !static_cpu_has(X86_FEATURE_PAT)))
    - return NULL;
    -
    - /* A single page can always be kmapped */
    - if (n_pte == 1 && type == I915_MAP_WB) {
    - struct page *page = sg_page(sgt->sgl);
    -
    + switch (type) {
    + default:
    + MISSING_CASE(type);
    + fallthrough; /* to use PAGE_KERNEL anyway */
    + case I915_MAP_WB:
    /*
    * On 32b, highmem using a finite set of indirect PTE (i.e.
    * vmap) to provide virtual mappings of the high pages.
    @@ -277,30 +264,8 @@ static void *i915_gem_object_map(struct drm_i915_gem_object *obj,
    * So if the page is beyond the 32b boundary, make an explicit
    * vmap.
    */
    - if (!PageHighMem(page))
    - return page_address(page);
    - }
    -
    - mem = stack;
    - if (n_pte > ARRAY_SIZE(stack)) {
    - /* Too big for stack -- allocate temporary array instead */
    - mem = kvmalloc_array(n_pte, sizeof(*mem), GFP_KERNEL);
    - if (!mem)
    - return NULL;
    - }
    -
    - area = alloc_vm_area(obj->base.size, mem);
    - if (!area) {
    - if (mem != stack)
    - kvfree(mem);
    - return NULL;
    - }
    -
    - switch (type) {
    - default:
    - MISSING_CASE(type);
    - fallthrough; /* to use PAGE_KERNEL anyway */
    - case I915_MAP_WB:
    + if (n_pages == 1 && !PageHighMem(sg_page(obj->mm.pages->sgl)))
    + return page_address(sg_page(obj->mm.pages->sgl));
    pgprot = PAGE_KERNEL;
    break;
    case I915_MAP_WC:
    @@ -308,30 +273,49 @@ static void *i915_gem_object_map(struct drm_i915_gem_object *obj,
    break;
    }

    - if (i915_gem_object_has_struct_page(obj)) {
    - struct sgt_iter iter;
    - struct page *page;
    - pte_t **ptes = mem;
    + if (n_pages > ARRAY_SIZE(stack)) {
    + /* Too big for stack -- allocate temporary array instead */
    + pages = kvmalloc_array(n_pages, sizeof(*pages), GFP_KERNEL);
    + if (!pages)
    + return NULL;
    + }

    - for_each_sgt_page(page, iter, sgt)
    - **ptes++ = mk_pte(page, pgprot);
    - } else {
    - resource_size_t iomap;
    - struct sgt_iter iter;
    - pte_t **ptes = mem;
    - dma_addr_t addr;
    + i = 0;
    + for_each_sgt_page(page, iter, obj->mm.pages)
    + pages[i++] = page;
    + vaddr = vmap(pages, n_pages, 0, pgprot);
    + if (pages != stack)
    + kvfree(pages);
    + return vaddr;
    +}

    - iomap = obj->mm.region->iomap.base;
    - iomap -= obj->mm.region->region.start;
    +static void *i915_gem_object_map_pfn(struct drm_i915_gem_object *obj,
    + enum i915_map_type type)
    +{
    + resource_size_t iomap = obj->mm.region->iomap.base -
    + obj->mm.region->region.start;
    + unsigned long n_pfn = obj->base.size >> PAGE_SHIFT;
    + unsigned long stack[32], *pfns = stack, i;
    + struct sgt_iter iter;
    + dma_addr_t addr;
    + void *vaddr;
    +
    + if (type != I915_MAP_WC)
    + return NULL;

    - for_each_sgt_daddr(addr, iter, sgt)
    - **ptes++ = iomap_pte(iomap, addr, pgprot);
    + if (n_pfn > ARRAY_SIZE(stack)) {
    + /* Too big for stack -- allocate temporary array instead */
    + pfns = kvmalloc_array(n_pfn, sizeof(*pfns), GFP_KERNEL);
    + if (!pfns)
    + return NULL;
    }

    - if (mem != stack)
    - kvfree(mem);
    -
    - return area->addr;
    + for_each_sgt_daddr(addr, iter, obj->mm.pages)
    + pfns[i++] = (iomap + addr) >> PAGE_SHIFT;
    + vaddr = vmap_pfn(pfns, n_pfn, pgprot_writecombine(PAGE_KERNEL_IO));
    + if (pfns != stack)
    + kvfree(pfns);
    + return vaddr;
    }

    /* get, pin, and map the pages of the object into kernel space */
    @@ -383,7 +367,13 @@ void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj,
    }

    if (!ptr) {
    - ptr = i915_gem_object_map(obj, type);
    + if (GEM_WARN_ON(type == I915_MAP_WC &&
    + !static_cpu_has(X86_FEATURE_PAT)))
    + ptr = NULL;
    + else if (i915_gem_object_has_struct_page(obj))
    + ptr = i915_gem_object_map_page(obj, type);
    + else
    + ptr = i915_gem_object_map_pfn(obj, type);
    if (!ptr) {
    err = -ENOMEM;
    goto err_unpin;
    --
    2.28.0
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