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drm/i915/gtt: Convert vm->scratch into an array

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Each level has its own scratch. Make the levels more obvious by forgoing
the fancy similarly names and replace them with a number. 0 is the bottom
most level, the physical page used for actual data; 1+ are the page
directories.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190712094327.24437-5-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2019-07-12 10:43:26 +01:00
parent 2776326457
commit c03cbe4c0a
2 changed files with 103 additions and 124 deletions
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211
drivers/gpu/drm/i915/i915_gem_gtt.c
View File

@ -633,7 +633,7 @@ setup_scratch_page(struct i915_address_space *vm, gfp_t gfp)
gfp |= __GFP_ZERO | __GFP_RETRY_MAYFAIL;
do {
int order = get_order(size);
unsigned int order = get_order(size);
struct page *page;
dma_addr_t addr;
@ -652,8 +652,8 @@ setup_scratch_page(struct i915_address_space *vm, gfp_t gfp)
if (unlikely(!IS_ALIGNED(addr, size)))
goto unmap_page;
vm->scratch_page.page = page;
vm->scratch_page.daddr = addr;
vm->scratch[0].base.page = page;
vm->scratch[0].base.daddr = addr;
vm->scratch_order = order;
return 0;
@ -672,8 +672,8 @@ skip:
static void cleanup_scratch_page(struct i915_address_space *vm)
{
struct i915_page_dma *p = &vm->scratch_page;
int order = vm->scratch_order;
struct i915_page_dma *p = px_base(&vm->scratch[0]);
unsigned int order = vm->scratch_order;
dma_unmap_page(vm->dma, p->daddr, BIT(order) << PAGE_SHIFT,
PCI_DMA_BIDIRECTIONAL);
@ -682,15 +682,16 @@ static void cleanup_scratch_page(struct i915_address_space *vm)
static void free_scratch(struct i915_address_space *vm)
{
if (!vm->scratch_page.daddr) /* set to 0 on clones */
int i;
if (!px_dma(&vm->scratch[0])) /* set to 0 on clones */
return;
if (vm->scratch_pdp.daddr)
cleanup_page_dma(vm, &vm->scratch_pdp);
if (vm->scratch_pd.daddr)
cleanup_page_dma(vm, &vm->scratch_pd);
if (vm->scratch_pt.daddr)
cleanup_page_dma(vm, &vm->scratch_pt);
for (i = 1; i <= vm->top; i++) {
if (!px_dma(&vm->scratch[i]))
break;
cleanup_page_dma(vm, px_base(&vm->scratch[i]));
}
cleanup_scratch_page(vm);
}
@ -752,9 +753,9 @@ static void free_pd(struct i915_address_space *vm, struct i915_page_dma *pd)
#define free_px(vm, px) free_pd(vm, px_base(px))
static void init_pd(struct i915_page_directory *pd,
struct i915_page_dma *scratch)
struct i915_page_scratch *scratch)
{
fill_px(pd, gen8_pde_encode(scratch->daddr, I915_CACHE_LLC));
fill_px(pd, scratch->encode);
memset_p(pd->entry, scratch, 512);
}
@ -782,30 +783,26 @@ __set_pd_entry(struct i915_page_directory * const pd,
write_dma_entry(px_base(pd), pde, encode(to->daddr, I915_CACHE_LLC));
}
static inline void
__clear_pd_entry(struct i915_page_directory * const pd,
const unsigned short pde,
struct i915_page_dma * const to,
u64 (*encode)(const dma_addr_t, const enum i915_cache_level))
{
GEM_BUG_ON(atomic_read(px_used(pd)) == 0);
write_dma_entry(px_base(pd), pde, encode(to->daddr, I915_CACHE_LLC));
pd->entry[pde] = to;
atomic_dec(px_used(pd));
}
#define set_pd_entry(pd, pde, to) \
__set_pd_entry((pd), (pde), px_base(to), gen8_pde_encode)
#define clear_pd_entry(pd, pde, to) \
__clear_pd_entry((pd), (pde), (to), gen8_pde_encode)
static inline void
clear_pd_entry(struct i915_page_directory * const pd,
const unsigned short pde,
struct i915_page_scratch * const scratch)
{
GEM_BUG_ON(atomic_read(px_used(pd)) == 0);
write_dma_entry(px_base(pd), pde, scratch->encode);
pd->entry[pde] = scratch;
atomic_dec(px_used(pd));
}
static bool
release_pd_entry(struct i915_page_directory * const pd,
const unsigned short pde,
struct i915_page_table * const pt,
struct i915_page_dma * const scratch)
struct i915_page_scratch * const scratch)
{
bool free = false;
@ -915,7 +912,7 @@ static void gen8_free_page_tables(struct i915_address_space *vm,
int i;
for (i = 0; i < I915_PDES; i++) {
if (pd->entry[i] != &vm->scratch_pt)
if (pd->entry[i] != &vm->scratch[1])
free_pd(vm, pd->entry[i]);
}
}
@ -927,7 +924,7 @@ static void gen8_ppgtt_cleanup_3lvl(struct i915_address_space *vm,
int i;
for (i = 0; i < pdpes; i++) {
if (pdp->entry[i] == &vm->scratch_pd)
if (pdp->entry[i] == &vm->scratch[2])
continue;
gen8_free_page_tables(vm, pdp->entry[i]);
@ -945,7 +942,7 @@ static void gen8_ppgtt_cleanup_4lvl(struct i915_ppgtt *ppgtt)
for (i = 0; i < GEN8_PML4ES_PER_PML4; i++) {
struct i915_page_directory *pdp = i915_pdp_entry(pml4, i);
if (px_base(pdp) == &ppgtt->vm.scratch_pdp)
if (px_base(pdp) == px_base(&ppgtt->vm.scratch[3]))
continue;
gen8_ppgtt_cleanup_3lvl(&ppgtt->vm, pdp);
@ -981,7 +978,9 @@ static void gen8_ppgtt_clear_pt(const struct i915_address_space *vm,
gen8_pte_t *vaddr;
vaddr = kmap_atomic_px(pt);
memset64(vaddr + gen8_pte_index(start), vm->scratch_pte, num_entries);
memset64(vaddr + gen8_pte_index(start),
vm->scratch[0].encode,
num_entries);
kunmap_atomic(vaddr);
GEM_BUG_ON(num_entries > atomic_read(&pt->used));
@ -997,11 +996,11 @@ static void gen8_ppgtt_clear_pd(struct i915_address_space *vm,
u32 pde;
gen8_for_each_pde(pt, pd, start, length, pde) {
GEM_BUG_ON(px_base(pt) == &vm->scratch_pt);
GEM_BUG_ON(px_base(pt) == px_base(&vm->scratch[1]));
atomic_inc(&pt->used);
gen8_ppgtt_clear_pt(vm, pt, start, length);
if (release_pd_entry(pd, pde, pt, &vm->scratch_pt))
if (release_pd_entry(pd, pde, pt, &vm->scratch[1]))
free_px(vm, pt);
}
}
@ -1017,11 +1016,11 @@ static void gen8_ppgtt_clear_pdp(struct i915_address_space *vm,
unsigned int pdpe;
gen8_for_each_pdpe(pd, pdp, start, length, pdpe) {
GEM_BUG_ON(px_base(pd) == &vm->scratch_pd);
GEM_BUG_ON(px_base(pd) == px_base(&vm->scratch[2]));
atomic_inc(px_used(pd));
gen8_ppgtt_clear_pd(vm, pd, start, length);
if (release_pd_entry(pdp, pdpe, &pd->pt, &vm->scratch_pd))
if (release_pd_entry(pdp, pdpe, &pd->pt, &vm->scratch[2]))
free_px(vm, pd);
}
}
@ -1047,16 +1046,15 @@ static void gen8_ppgtt_clear_4lvl(struct i915_address_space *vm,
GEM_BUG_ON(!i915_vm_is_4lvl(vm));
gen8_for_each_pml4e(pdp, pml4, start, length, pml4e) {
GEM_BUG_ON(px_base(pdp) == &vm->scratch_pdp);
GEM_BUG_ON(px_base(pdp) == px_base(&vm->scratch[3]));
atomic_inc(px_used(pdp));
gen8_ppgtt_clear_pdp(vm, pdp, start, length);
if (release_pd_entry(pml4, pml4e, &pdp->pt, &vm->scratch_pdp))
if (release_pd_entry(pml4, pml4e, &pdp->pt, &vm->scratch[3]))
free_px(vm, pdp);
}
}
static int gen8_ppgtt_alloc_pd(struct i915_address_space *vm,
struct i915_page_directory *pd,
u64 start, u64 length)
@ -1070,7 +1068,7 @@ static int gen8_ppgtt_alloc_pd(struct i915_address_space *vm,
gen8_for_each_pde(pt, pd, start, length, pde) {
const int count = gen8_pte_count(start, length);
if (px_base(pt) == &vm->scratch_pt) {
if (px_base(pt) == px_base(&vm->scratch[1])) {
spin_unlock(&pd->lock);
pt = fetch_and_zero(&alloc);
@ -1082,10 +1080,10 @@ static int gen8_ppgtt_alloc_pd(struct i915_address_space *vm,
}
if (count < GEN8_PTES || intel_vgpu_active(vm->i915))
fill_px(pt, vm->scratch_pte);
fill_px(pt, vm->scratch[0].encode);
spin_lock(&pd->lock);
if (pd->entry[pde] == &vm->scratch_pt) {
if (pd->entry[pde] == &vm->scratch[1]) {
set_pd_entry(pd, pde, pt);
} else {
alloc = pt;
@ -1117,7 +1115,7 @@ static int gen8_ppgtt_alloc_pdp(struct i915_address_space *vm,
spin_lock(&pdp->lock);
gen8_for_each_pdpe(pd, pdp, start, length, pdpe) {
if (px_base(pd) == &vm->scratch_pd) {
if (px_base(pd) == px_base(&vm->scratch[2])) {
spin_unlock(&pdp->lock);
pd = fetch_and_zero(&alloc);
@ -1128,10 +1126,10 @@ static int gen8_ppgtt_alloc_pdp(struct i915_address_space *vm,
goto unwind;
}
init_pd(pd, &vm->scratch_pt);
init_pd(pd, &vm->scratch[1]);
spin_lock(&pdp->lock);
if (pdp->entry[pdpe] == &vm->scratch_pd) {
if (pdp->entry[pdpe] == &vm->scratch[2]) {
set_pd_entry(pdp, pdpe, pd);
} else {
alloc = pd;
@ -1152,7 +1150,7 @@ static int gen8_ppgtt_alloc_pdp(struct i915_address_space *vm,
goto out;
unwind_pd:
if (release_pd_entry(pdp, pdpe, &pd->pt, &vm->scratch_pd))
if (release_pd_entry(pdp, pdpe, &pd->pt, &vm->scratch[2]))
free_px(vm, pd);
unwind:
gen8_ppgtt_clear_pdp(vm, pdp, from, start - from);
@ -1181,7 +1179,7 @@ static int gen8_ppgtt_alloc_4lvl(struct i915_address_space *vm,
spin_lock(&pml4->lock);
gen8_for_each_pml4e(pdp, pml4, start, length, pml4e) {
if (px_base(pdp) == &vm->scratch_pdp) {
if (px_base(pdp) == px_base(&vm->scratch[3])) {
spin_unlock(&pml4->lock);
pdp = fetch_and_zero(&alloc);
@ -1192,10 +1190,10 @@ static int gen8_ppgtt_alloc_4lvl(struct i915_address_space *vm,
goto unwind;
}
init_pd(pdp, &vm->scratch_pd);
init_pd(pdp, &vm->scratch[2]);
spin_lock(&pml4->lock);
if (pml4->entry[pml4e] == &vm->scratch_pdp) {
if (pml4->entry[pml4e] == &vm->scratch[3]) {
set_pd_entry(pml4, pml4e, pdp);
} else {
alloc = pdp;
@ -1216,7 +1214,7 @@ static int gen8_ppgtt_alloc_4lvl(struct i915_address_space *vm,
goto out;
unwind_pdp:
if (release_pd_entry(pml4, pml4e, &pdp->pt, &vm->scratch_pdp))
if (release_pd_entry(pml4, pml4e, &pdp->pt, &vm->scratch[3]))
free_px(vm, pdp);
unwind:
gen8_ppgtt_clear_4lvl(vm, from, start - from);
@ -1430,7 +1428,7 @@ static void gen8_ppgtt_insert_huge_entries(struct i915_vma *vma,
if (I915_SELFTEST_ONLY(vma->vm->scrub_64K)) {
u16 i;
encode = vma->vm->scratch_pte;
encode = vma->vm->scratch[0].encode;
vaddr = kmap_atomic_px(i915_pt_entry(pd,
idx.pde));
@ -1473,6 +1471,7 @@ static void gen8_ppgtt_insert_4lvl(struct i915_address_space *vm,
static int gen8_init_scratch(struct i915_address_space *vm)
{
int ret;
int i;
/*
* If everybody agrees to not to write into the scratch page,
@ -1486,10 +1485,8 @@ static int gen8_init_scratch(struct i915_address_space *vm)
GEM_BUG_ON(!clone->has_read_only);
vm->scratch_order = clone->scratch_order;
vm->scratch_pte = clone->scratch_pte;
vm->scratch_pt = clone->scratch_pt;
vm->scratch_pd = clone->scratch_pd;
vm->scratch_pdp = clone->scratch_pdp;
memcpy(vm->scratch, clone->scratch, sizeof(vm->scratch));
px_dma(&vm->scratch[0]) = 0; /* no xfer of ownership */
return 0;
}
@ -1497,43 +1494,25 @@ static int gen8_init_scratch(struct i915_address_space *vm)
if (ret)
return ret;
vm->scratch_pte =
gen8_pte_encode(vm->scratch_page.daddr,
I915_CACHE_LLC,
vm->has_read_only);
vm->scratch[0].encode =
gen8_pte_encode(px_dma(&vm->scratch[0]),
I915_CACHE_LLC, vm->has_read_only);
if (unlikely(setup_page_dma(vm, &vm->scratch_pt))) {
ret = -ENOMEM;
goto free_scratch_page;
}
fill_px(&vm->scratch_pt, vm->scratch_pte);
for (i = 1; i <= vm->top; i++) {
if (unlikely(setup_page_dma(vm, px_base(&vm->scratch[i]))))
goto free_scratch;
if (unlikely(setup_page_dma(vm, &vm->scratch_pd))) {
ret = -ENOMEM;
goto free_pt;
}
fill_px(&vm->scratch_pd,
gen8_pde_encode(vm->scratch_pt.daddr, I915_CACHE_LLC));
if (i915_vm_is_4lvl(vm)) {
if (unlikely(setup_page_dma(vm, &vm->scratch_pdp))) {
ret = -ENOMEM;
goto free_pd;
}
fill_px(&vm->scratch_pdp,
gen8_pde_encode(vm->scratch_pd.daddr, I915_CACHE_LLC));
fill_px(&vm->scratch[i], vm->scratch[i - 1].encode);
vm->scratch[i].encode =
gen8_pde_encode(px_dma(&vm->scratch[i]),
I915_CACHE_LLC);
}
return 0;
free_pd:
cleanup_page_dma(vm, &vm->scratch_pd);
free_pt:
cleanup_page_dma(vm, &vm->scratch_pt);
free_scratch_page:
cleanup_scratch_page(vm);
return ret;
free_scratch:
free_scratch(vm);
return -ENOMEM;
}
static int gen8_preallocate_top_level_pdp(struct i915_ppgtt *ppgtt)
@ -1550,7 +1529,7 @@ static int gen8_preallocate_top_level_pdp(struct i915_ppgtt *ppgtt)
if (IS_ERR(pd))
goto unwind;
init_pd(pd, &vm->scratch_pt);
init_pd(pd, &vm->scratch[1]);
set_pd_entry(pdp, pdpe, pd);
}
@ -1581,16 +1560,15 @@ static void ppgtt_init(struct i915_ppgtt *ppgtt, struct intel_gt *gt)
static void init_pd_n(struct i915_address_space *vm,
struct i915_page_directory *pd,
struct i915_page_dma *to,
struct i915_page_scratch *scratch,
const unsigned int entries)
{
const u64 daddr = gen8_pde_encode(to->daddr, I915_CACHE_LLC);
u64 * const vaddr = kmap_atomic_px(pd);
memset64(vaddr, daddr, entries);
memset64(vaddr, scratch->encode, entries);
kunmap_atomic(vaddr);
memset_p(pd->entry, to, entries);
memset_p(pd->entry, scratch, entries);
}
static struct i915_page_directory *
@ -1601,7 +1579,7 @@ gen8_alloc_top_pd(struct i915_address_space *vm)
if (i915_vm_is_4lvl(vm)) {
pd = alloc_pd(vm);
if (!IS_ERR(pd))
init_pd(pd, &vm->scratch_pdp);
init_pd(pd, &vm->scratch[3]);
return pd;
}
@ -1618,7 +1596,7 @@ gen8_alloc_top_pd(struct i915_address_space *vm)
return ERR_PTR(-ENOMEM);
}
init_pd_n(vm, pd, &vm->scratch_pd, GEN8_3LVL_PDPES);
init_pd_n(vm, pd, &vm->scratch[2], GEN8_3LVL_PDPES);
return pd;
}
@ -1766,7 +1744,7 @@ static void gen6_ppgtt_clear_range(struct i915_address_space *vm,
{
struct gen6_ppgtt * const ppgtt = to_gen6_ppgtt(i915_vm_to_ppgtt(vm));
const unsigned int first_entry = start / I915_GTT_PAGE_SIZE;
const gen6_pte_t scratch_pte = vm->scratch_pte;
const gen6_pte_t scratch_pte = vm->scratch[0].encode;
unsigned int pde = first_entry / GEN6_PTES;
unsigned int pte = first_entry % GEN6_PTES;
unsigned int num_entries = length / I915_GTT_PAGE_SIZE;
@ -1777,7 +1755,7 @@ static void gen6_ppgtt_clear_range(struct i915_address_space *vm,
const unsigned int count = min(num_entries, GEN6_PTES - pte);
gen6_pte_t *vaddr;
GEM_BUG_ON(px_base(pt) == &vm->scratch_pt);
GEM_BUG_ON(px_base(pt) == px_base(&vm->scratch[1]));
num_entries -= count;
@ -1814,7 +1792,7 @@ static void gen6_ppgtt_insert_entries(struct i915_address_space *vm,
struct sgt_dma iter = sgt_dma(vma);
gen6_pte_t *vaddr;
GEM_BUG_ON(pd->entry[act_pt] == &vm->scratch_pt);
GEM_BUG_ON(pd->entry[act_pt] == &vm->scratch[1]);
vaddr = kmap_atomic_px(i915_pt_entry(pd, act_pt));
do {
@ -1859,7 +1837,7 @@ static int gen6_alloc_va_range(struct i915_address_space *vm,
gen6_for_each_pde(pt, pd, start, length, pde) {
const unsigned int count = gen6_pte_count(start, length);
if (px_base(pt) == &vm->scratch_pt) {
if (px_base(pt) == px_base(&vm->scratch[1])) {
spin_unlock(&pd->lock);
pt = fetch_and_zero(&alloc);
@ -1870,10 +1848,10 @@ static int gen6_alloc_va_range(struct i915_address_space *vm,
goto unwind_out;
}
fill32_px(pt, vm->scratch_pte);
fill32_px(pt, vm->scratch[0].encode);
spin_lock(&pd->lock);
if (pd->entry[pde] == &vm->scratch_pt) {
if (pd->entry[pde] == &vm->scratch[1]) {
pd->entry[pde] = pt;
if (i915_vma_is_bound(ppgtt->vma,
I915_VMA_GLOBAL_BIND)) {
@ -1910,26 +1888,23 @@ static int gen6_ppgtt_init_scratch(struct gen6_ppgtt *ppgtt)
{
struct i915_address_space * const vm = &ppgtt->base.vm;
struct i915_page_directory * const pd = ppgtt->base.pd;
struct i915_page_table *unused;
u32 pde;
int ret;
ret = setup_scratch_page(vm, __GFP_HIGHMEM);
if (ret)
return ret;
vm->scratch_pte = vm->pte_encode(vm->scratch_page.daddr,
I915_CACHE_NONE,
PTE_READ_ONLY);
vm->scratch[0].encode =
vm->pte_encode(px_dma(&vm->scratch[0]),
I915_CACHE_NONE, PTE_READ_ONLY);
if (unlikely(setup_page_dma(vm, &vm->scratch_pt))) {
if (unlikely(setup_page_dma(vm, px_base(&vm->scratch[1])))) {
cleanup_scratch_page(vm);
return -ENOMEM;
}
fill32_px(&vm->scratch_pt, vm->scratch_pte);
gen6_for_all_pdes(unused, pd, pde)
pd->entry[pde] = &vm->scratch_pt;
fill32_px(&vm->scratch[1], vm->scratch[0].encode);
memset_p(pd->entry, &vm->scratch[1], I915_PDES);
return 0;
}
@ -1937,11 +1912,13 @@ static int gen6_ppgtt_init_scratch(struct gen6_ppgtt *ppgtt)
static void gen6_ppgtt_free_pd(struct gen6_ppgtt *ppgtt)
{
struct i915_page_directory * const pd = ppgtt->base.pd;
struct i915_page_dma * const scratch =
px_base(&ppgtt->base.vm.scratch[1]);
struct i915_page_table *pt;
u32 pde;
gen6_for_all_pdes(pt, pd, pde)
if (px_base(pt) != &ppgtt->base.vm.scratch_pt)
if (px_base(pt) != scratch)
free_px(&ppgtt->base.vm, pt);
}
@ -1999,7 +1976,8 @@ static void pd_vma_unbind(struct i915_vma *vma)
{
struct gen6_ppgtt *ppgtt = vma->private;
struct i915_page_directory * const pd = ppgtt->base.pd;
struct i915_page_dma * const scratch = &ppgtt->base.vm.scratch_pt;
struct i915_page_dma * const scratch =
px_base(&ppgtt->base.vm.scratch[1]);
struct i915_page_table *pt;
unsigned int pde;
@ -2405,7 +2383,7 @@ static void gen8_ggtt_clear_range(struct i915_address_space *vm,
struct i915_ggtt *ggtt = i915_vm_to_ggtt(vm);
unsigned first_entry = start / I915_GTT_PAGE_SIZE;
unsigned num_entries = length / I915_GTT_PAGE_SIZE;
const gen8_pte_t scratch_pte = vm->scratch_pte;
const gen8_pte_t scratch_pte = vm->scratch[0].encode;
gen8_pte_t __iomem *gtt_base =
(gen8_pte_t __iomem *)ggtt->gsm + first_entry;
const int max_entries = ggtt_total_entries(ggtt) - first_entry;
@ -2530,8 +2508,7 @@ static void gen6_ggtt_clear_range(struct i915_address_space *vm,
first_entry, num_entries, max_entries))
num_entries = max_entries;
scratch_pte = vm->scratch_pte;
scratch_pte = vm->scratch[0].encode;
for (i = 0; i < num_entries; i++)
iowrite32(scratch_pte, &gtt_base[i]);
}
@ -3005,8 +2982,8 @@ static int ggtt_probe_common(struct i915_ggtt *ggtt, u64 size)
return ret;
}
ggtt->vm.scratch_pte =
ggtt->vm.pte_encode(ggtt->vm.scratch_page.daddr,
ggtt->vm.scratch[0].encode =
ggtt->vm.pte_encode(px_dma(&ggtt->vm.scratch[0]),
I915_CACHE_NONE, 0);
return 0;

16
drivers/gpu/drm/i915/i915_gem_gtt.h
View File

@ -239,6 +239,11 @@ struct i915_page_dma {
};
};
struct i915_page_scratch {
struct i915_page_dma base;
u64 encode;
};
struct i915_page_table {
struct i915_page_dma base;
atomic_t used;
@ -259,9 +264,10 @@ struct i915_page_directory {
#define px_base(px) \
__px_choose_expr(px, struct i915_page_dma *, __x, \
__px_choose_expr(px, struct i915_page_scratch *, &__x->base, \
__px_choose_expr(px, struct i915_page_table *, &__x->base, \
__px_choose_expr(px, struct i915_page_directory *, &__x->pt.base, \
(void)0)))
(void)0))))
#define px_dma(px) (px_base(px)->daddr)
#define px_pt(px) \
@ -316,12 +322,8 @@ struct i915_address_space {
#define VM_CLASS_GGTT 0
#define VM_CLASS_PPGTT 1
u64 scratch_pte;
int scratch_order;
struct i915_page_dma scratch_page;
struct i915_page_dma scratch_pt;
struct i915_page_dma scratch_pd;
struct i915_page_dma scratch_pdp; /* GEN8+ & 48b PPGTT */
struct i915_page_scratch scratch[4];
unsigned int scratch_order;
unsigned int top;
/**