[PATCH 08/11] drm/i915: use vmap in i915_gem_object_map

[Christoph Hellwig <hch@xxxxxx>]

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@xxxxxx>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
 drivers/gpu/drm/i915/Kconfig              |   1 +
 drivers/gpu/drm/i915/gem/i915_gem_pages.c | 127 ++++++++++------------
 2 files changed, 60 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..f60ca6dc911f29 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 +273,50 @@ 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;
+       i = 0;
+       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 +368,13 @@ 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