[Intel-gfx] [PATCH v4] drm/i915/gtt: Read-only pages for insert_entries on bdw+
Chris Wilson
chris at chris-wilson.co.uk
Fri Jun 15 08:26:09 UTC 2018
From: Jon Bloomfield <jon.bloomfield at intel.com>
Hook up the flags to allow read-only ppGTT mappings for gen8+
v2: Include a selftest to check that writes to a readonly PTE are
dropped
v3: Don't duplicate cpu_check() as we can just reuse it, and even worse
don't wholesale copy the theory-of-operation comment from igt_ctx_exec
without changing it to explain the intention behind the new test!
v4: Joonas really likes magic mystery values
Signed-off-by: Jon Bloomfield <jon.bloomfield at intel.com>
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Cc: Matthew Auld <matthew.william.auld at gmail.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Reviewed-by: Matthew Auld <matthew.william.auld at gmail.com>
---
drivers/gpu/drm/i915/i915_gem_gtt.c | 45 ++++---
drivers/gpu/drm/i915/i915_gem_gtt.h | 7 +-
drivers/gpu/drm/i915/intel_ringbuffer.c | 11 +-
.../gpu/drm/i915/selftests/i915_gem_context.c | 112 +++++++++++++++++-
4 files changed, 153 insertions(+), 22 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 705cf1c04bba..deddf15db24a 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -196,7 +196,7 @@ static int ppgtt_bind_vma(struct i915_vma *vma,
return err;
}
- /* Currently applicable only to VLV */
+ /* Applicable to VLV, and gen8+ */
pte_flags = 0;
if (vma->obj->gt_ro)
pte_flags |= PTE_READ_ONLY;
@@ -952,10 +952,11 @@ gen8_ppgtt_insert_pte_entries(struct i915_hw_ppgtt *ppgtt,
struct i915_page_directory_pointer *pdp,
struct sgt_dma *iter,
struct gen8_insert_pte *idx,
- enum i915_cache_level cache_level)
+ enum i915_cache_level cache_level,
+ u32 flags)
{
struct i915_page_directory *pd;
- const gen8_pte_t pte_encode = gen8_pte_encode(0, cache_level, 0);
+ const gen8_pte_t pte_encode = gen8_pte_encode(0, cache_level, flags);
gen8_pte_t *vaddr;
bool ret;
@@ -1006,14 +1007,14 @@ gen8_ppgtt_insert_pte_entries(struct i915_hw_ppgtt *ppgtt,
static void gen8_ppgtt_insert_3lvl(struct i915_address_space *vm,
struct i915_vma *vma,
enum i915_cache_level cache_level,
- u32 unused)
+ u32 flags)
{
struct i915_hw_ppgtt *ppgtt = i915_vm_to_ppgtt(vm);
struct sgt_dma iter = sgt_dma(vma);
struct gen8_insert_pte idx = gen8_insert_pte(vma->node.start);
gen8_ppgtt_insert_pte_entries(ppgtt, &ppgtt->pdp, &iter, &idx,
- cache_level);
+ cache_level, flags);
vma->page_sizes.gtt = I915_GTT_PAGE_SIZE;
}
@@ -1021,9 +1022,10 @@ static void gen8_ppgtt_insert_3lvl(struct i915_address_space *vm,
static void gen8_ppgtt_insert_huge_entries(struct i915_vma *vma,
struct i915_page_directory_pointer **pdps,
struct sgt_dma *iter,
- enum i915_cache_level cache_level)
+ enum i915_cache_level cache_level,
+ u32 flags)
{
- const gen8_pte_t pte_encode = gen8_pte_encode(0, cache_level, 0);
+ const gen8_pte_t pte_encode = gen8_pte_encode(0, cache_level, flags);
u64 start = vma->node.start;
dma_addr_t rem = iter->sg->length;
@@ -1139,19 +1141,21 @@ static void gen8_ppgtt_insert_huge_entries(struct i915_vma *vma,
static void gen8_ppgtt_insert_4lvl(struct i915_address_space *vm,
struct i915_vma *vma,
enum i915_cache_level cache_level,
- u32 unused)
+ u32 flags)
{
struct i915_hw_ppgtt *ppgtt = i915_vm_to_ppgtt(vm);
struct sgt_dma iter = sgt_dma(vma);
struct i915_page_directory_pointer **pdps = ppgtt->pml4.pdps;
if (vma->page_sizes.sg > I915_GTT_PAGE_SIZE) {
- gen8_ppgtt_insert_huge_entries(vma, pdps, &iter, cache_level);
+ gen8_ppgtt_insert_huge_entries(vma, pdps, &iter, cache_level,
+ flags);
} else {
struct gen8_insert_pte idx = gen8_insert_pte(vma->node.start);
while (gen8_ppgtt_insert_pte_entries(ppgtt, pdps[idx.pml4e++],
- &iter, &idx, cache_level))
+ &iter, &idx, cache_level,
+ flags))
GEM_BUG_ON(idx.pml4e >= GEN8_PML4ES_PER_PML4);
vma->page_sizes.gtt = I915_GTT_PAGE_SIZE;
@@ -1564,6 +1568,9 @@ static struct i915_hw_ppgtt *gen8_ppgtt_create(struct drm_i915_private *i915)
1ULL << 48 :
1ULL << 32;
+ /* From bdw, there is support for read-only pages in the PPGTT */
+ ppgtt->vm.has_read_only = true;
+
/* There are only few exceptions for gen >=6. chv and bxt.
* And we are not sure about the latter so play safe for now.
*/
@@ -2400,7 +2407,7 @@ static void gen8_ggtt_insert_page(struct i915_address_space *vm,
static void gen8_ggtt_insert_entries(struct i915_address_space *vm,
struct i915_vma *vma,
enum i915_cache_level level,
- u32 unused)
+ u32 flags)
{
struct i915_ggtt *ggtt = i915_vm_to_ggtt(vm);
struct sgt_iter sgt_iter;
@@ -2408,6 +2415,9 @@ static void gen8_ggtt_insert_entries(struct i915_address_space *vm,
const gen8_pte_t pte_encode = gen8_pte_encode(0, level, 0);
dma_addr_t addr;
+ /* The GTT does not support read-only mappings */
+ GEM_BUG_ON(flags & PTE_READ_ONLY);
+
gtt_entries = (gen8_pte_t __iomem *)ggtt->gsm;
gtt_entries += vma->node.start >> PAGE_SHIFT;
for_each_sgt_dma(addr, sgt_iter, vma->pages)
@@ -2534,13 +2544,14 @@ struct insert_entries {
struct i915_address_space *vm;
struct i915_vma *vma;
enum i915_cache_level level;
+ u32 flags;
};
static int bxt_vtd_ggtt_insert_entries__cb(void *_arg)
{
struct insert_entries *arg = _arg;
- gen8_ggtt_insert_entries(arg->vm, arg->vma, arg->level, 0);
+ gen8_ggtt_insert_entries(arg->vm, arg->vma, arg->level, arg->flags);
bxt_vtd_ggtt_wa(arg->vm);
return 0;
@@ -2549,9 +2560,9 @@ static int bxt_vtd_ggtt_insert_entries__cb(void *_arg)
static void bxt_vtd_ggtt_insert_entries__BKL(struct i915_address_space *vm,
struct i915_vma *vma,
enum i915_cache_level level,
- u32 unused)
+ u32 flags)
{
- struct insert_entries arg = { vm, vma, level };
+ struct insert_entries arg = { vm, vma, level, flags };
stop_machine(bxt_vtd_ggtt_insert_entries__cb, &arg, NULL);
}
@@ -2642,7 +2653,7 @@ static int ggtt_bind_vma(struct i915_vma *vma,
struct drm_i915_gem_object *obj = vma->obj;
u32 pte_flags;
- /* Currently applicable only to VLV */
+ /* Applicable to VLV (gen8+ do not support RO in the GGTT) */
pte_flags = 0;
if (obj->gt_ro)
pte_flags |= PTE_READ_ONLY;
@@ -3522,6 +3533,10 @@ int i915_ggtt_init_hw(struct drm_i915_private *dev_priv)
*/
mutex_lock(&dev_priv->drm.struct_mutex);
i915_address_space_init(&ggtt->vm, dev_priv, "[global]");
+
+ /* Only VLV supports read-only GGTT mappings */
+ ggtt->vm.has_read_only = IS_VALLEYVIEW(dev_priv);
+
if (!HAS_LLC(dev_priv) && !USES_PPGTT(dev_priv))
ggtt->vm.mm.color_adjust = i915_gtt_color_adjust;
mutex_unlock(&dev_priv->drm.struct_mutex);
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h
index 9a4824cae68d..f1f6d7076f12 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.h
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
@@ -325,7 +325,12 @@ struct i915_address_space {
struct list_head unbound_list;
struct pagevec free_pages;
- bool pt_kmap_wc;
+
+ /* Some systems require uncached updates of the page directories */
+ bool pt_kmap_wc:1;
+
+ /* Some systems support read-only mappings for GGTT and/or PPGTT */
+ bool has_read_only:1;
/* FIXME: Need a more generic return type */
gen6_pte_t (*pte_encode)(dma_addr_t addr,
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index ef3c76425843..8853a5e6d421 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1097,6 +1097,7 @@ void intel_ring_unpin(struct intel_ring *ring)
static struct i915_vma *
intel_ring_create_vma(struct drm_i915_private *dev_priv, int size)
{
+ struct i915_address_space *vm = &dev_priv->ggtt.vm;
struct drm_i915_gem_object *obj;
struct i915_vma *vma;
@@ -1106,10 +1107,14 @@ intel_ring_create_vma(struct drm_i915_private *dev_priv, int size)
if (IS_ERR(obj))
return ERR_CAST(obj);
- /* mark ring buffers as read-only from GPU side by default */
- obj->gt_ro = 1;
+ /*
+ * Mark ring buffers as read-only from GPU side (so no stray overwrites)
+ * if supported by the platform's GGTT.
+ */
+ if (vm->has_read_only)
+ obj->gt_ro = 1;
- vma = i915_vma_instance(obj, &dev_priv->ggtt.vm, NULL);
+ vma = i915_vma_instance(obj, vm, NULL);
if (IS_ERR(vma))
goto err;
diff --git a/drivers/gpu/drm/i915/selftests/i915_gem_context.c b/drivers/gpu/drm/i915/selftests/i915_gem_context.c
index 836f1af8b833..6fe4682eacf3 100644
--- a/drivers/gpu/drm/i915/selftests/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/selftests/i915_gem_context.c
@@ -23,6 +23,7 @@
*/
#include "../i915_selftest.h"
+#include "i915_random.h"
#include "igt_flush_test.h"
#include "mock_drm.h"
@@ -248,9 +249,9 @@ static int cpu_check(struct drm_i915_gem_object *obj, unsigned int max)
}
for (; m < DW_PER_PAGE; m++) {
- if (map[m] != 0xdeadbeef) {
+ if (map[m] != STACK_MAGIC) {
pr_err("Invalid value at page %d, offset %d: found %x expected %x\n",
- n, m, map[m], 0xdeadbeef);
+ n, m, map[m], STACK_MAGIC);
err = -EINVAL;
goto out_unmap;
}
@@ -306,7 +307,7 @@ create_test_object(struct i915_gem_context *ctx,
if (err)
return ERR_PTR(err);
- err = cpu_fill(obj, 0xdeadbeef);
+ err = cpu_fill(obj, STACK_MAGIC);
if (err) {
pr_err("Failed to fill object with cpu, err=%d\n",
err);
@@ -421,6 +422,110 @@ static int igt_ctx_exec(void *arg)
return err;
}
+static int igt_ctx_readonly(void *arg)
+{
+ struct drm_i915_private *i915 = arg;
+ struct drm_i915_gem_object *obj = NULL;
+ struct drm_file *file;
+ I915_RND_STATE(prng);
+ IGT_TIMEOUT(end_time);
+ LIST_HEAD(objects);
+ struct i915_gem_context *ctx;
+ struct i915_hw_ppgtt *ppgtt;
+ unsigned long ndwords, dw;
+ int err = -ENODEV;
+
+ /*
+ * Create a few read-only objects (with the occasional writable object)
+ * and try to write into these object checking that the GPU discards
+ * any write to a read-only object.
+ */
+
+ file = mock_file(i915);
+ if (IS_ERR(file))
+ return PTR_ERR(file);
+
+ mutex_lock(&i915->drm.struct_mutex);
+
+ ctx = i915_gem_create_context(i915, file->driver_priv);
+ if (IS_ERR(ctx)) {
+ err = PTR_ERR(ctx);
+ goto out_unlock;
+ }
+
+ ppgtt = ctx->ppgtt ?: i915->mm.aliasing_ppgtt;
+ if (!ppgtt || !ppgtt->vm.has_read_only) {
+ err = 0;
+ goto out_unlock;
+ }
+
+ ndwords = 0;
+ dw = 0;
+ while (!time_after(jiffies, end_time)) {
+ struct intel_engine_cs *engine;
+ unsigned int id;
+
+ for_each_engine(engine, i915, id) {
+ if (!intel_engine_can_store_dword(engine))
+ continue;
+
+ if (!obj) {
+ obj = create_test_object(ctx, file, &objects);
+ if (IS_ERR(obj)) {
+ err = PTR_ERR(obj);
+ goto out_unlock;
+ }
+
+ obj->gt_ro = prandom_u32_state(&prng);
+ }
+
+ intel_runtime_pm_get(i915);
+ err = gpu_fill(obj, ctx, engine, dw);
+ intel_runtime_pm_put(i915);
+ if (err) {
+ pr_err("Failed to fill dword %lu [%lu/%lu] with gpu (%s) in ctx %u [full-ppgtt? %s], err=%d\n",
+ ndwords, dw, max_dwords(obj),
+ engine->name, ctx->hw_id,
+ yesno(!!ctx->ppgtt), err);
+ goto out_unlock;
+ }
+
+ if (++dw == max_dwords(obj)) {
+ obj = NULL;
+ dw = 0;
+ }
+ ndwords++;
+ }
+ }
+ pr_info("Submitted %lu dwords (across %u engines)\n",
+ ndwords, INTEL_INFO(i915)->num_rings);
+
+ dw = 0;
+ list_for_each_entry(obj, &objects, st_link) {
+ unsigned int rem =
+ min_t(unsigned int, ndwords - dw, max_dwords(obj));
+ unsigned int num_writes;
+
+ num_writes = rem;
+ if (obj->gt_ro)
+ num_writes = 0;
+
+ err = cpu_check(obj, num_writes);
+ if (err)
+ break;
+
+ dw += rem;
+ }
+
+out_unlock:
+ if (igt_flush_test(i915, I915_WAIT_LOCKED))
+ err = -EIO;
+ mutex_unlock(&i915->drm.struct_mutex);
+
+ mock_file_free(i915, file);
+ return err;
+}
+
static __maybe_unused const char *
__engine_name(struct drm_i915_private *i915, unsigned int engines)
{
@@ -595,6 +700,7 @@ int i915_gem_context_live_selftests(struct drm_i915_private *dev_priv)
static const struct i915_subtest tests[] = {
SUBTEST(igt_switch_to_kernel_context),
SUBTEST(igt_ctx_exec),
+ SUBTEST(igt_ctx_readonly),
};
bool fake_alias = false;
int err;
--
2.17.1
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