Re: [PATCH 08/11] drm/i915: use vmap in i915_gem_object_map
From: Tvrtko Ursulin
Date: Fri Sep 25 2020 - 09:11:46 EST
On 24/09/2020 14:58, Christoph Hellwig wrote:
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>
---
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;
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Regards,
Tvrtko