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Message-ID: <74e101c2-39c7-a169-f7c4-8947517dde8b@collabora.com>
Date: Mon, 23 May 2022 16:52:21 +0100
From: Robert Beckett <bob.beckett@...labora.com>
To: Thomas Hellström
<thomas.hellstrom@...ux.intel.com>,
dri-devel@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
Jani Nikula <jani.nikula@...ux.intel.com>,
Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
Rodrigo Vivi <rodrigo.vivi@...el.com>,
Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
David Airlie <airlied@...ux.ie>,
Daniel Vetter <daniel@...ll.ch>
Cc: Matthew Auld <matthew.auld@...el.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] drm/i915: internal buffers use ttm backend
On 11/05/2022 15:14, Thomas Hellström wrote:
> On Tue, 2022-05-03 at 19:13 +0000, Robert Beckett wrote:
>> refactor internal buffer backend to allocate volatile pages via
>> ttm pool allocator
>>
>> Signed-off-by: Robert Beckett <bob.beckett@...labora.com>
>> ---
>> drivers/gpu/drm/i915/gem/i915_gem_internal.c | 264 ++++++++---------
>> --
>> drivers/gpu/drm/i915/gem/i915_gem_internal.h | 5 -
>> drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 12 +-
>> drivers/gpu/drm/i915/gem/i915_gem_ttm.h | 12 +-
>> 4 files changed, 125 insertions(+), 168 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_internal.c
>> b/drivers/gpu/drm/i915/gem/i915_gem_internal.c
>> index c698f95af15f..815ec9466cc0 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_internal.c
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_internal.c
>> @@ -4,156 +4,119 @@
>> * Copyright © 2014-2016 Intel Corporation
>> */
>>
>> -#include <linux/scatterlist.h>
>> -#include <linux/slab.h>
>> -#include <linux/swiotlb.h>
>> -
>> +#include <drm/ttm/ttm_bo_driver.h>
>> +#include <drm/ttm/ttm_placement.h>
>> +#include "drm/ttm/ttm_bo_api.h"
>> +#include "gem/i915_gem_internal.h"
>> +#include "gem/i915_gem_region.h"
>> +#include "gem/i915_gem_ttm.h"
>> #include "i915_drv.h"
>> -#include "i915_gem.h"
>> -#include "i915_gem_internal.h"
>> -#include "i915_gem_object.h"
>> -#include "i915_scatterlist.h"
>> -#include "i915_utils.h"
>> -
>> -#define QUIET (__GFP_NORETRY | __GFP_NOWARN)
>> -#define MAYFAIL (__GFP_RETRY_MAYFAIL | __GFP_NOWARN)
>> -
>> -static void internal_free_pages(struct sg_table *st)
>> -{
>> - struct scatterlist *sg;
>> -
>> - for (sg = st->sgl; sg; sg = __sg_next(sg)) {
>> - if (sg_page(sg))
>> - __free_pages(sg_page(sg), get_order(sg-
>>> length));
>> - }
>> -
>> - sg_free_table(st);
>> - kfree(st);
>> -}
>>
>> -static int i915_gem_object_get_pages_internal(struct
>> drm_i915_gem_object *obj)
>> +static int i915_internal_get_pages(struct drm_i915_gem_object *obj)
>> {
>> - struct drm_i915_private *i915 = to_i915(obj->base.dev);
>> - struct sg_table *st;
>> - struct scatterlist *sg;
>> - unsigned int sg_page_sizes;
>> - unsigned int npages;
>> - int max_order;
>> - gfp_t gfp;
>> -
>> - max_order = MAX_ORDER;
>> -#ifdef CONFIG_SWIOTLB
>> - if (is_swiotlb_active(obj->base.dev->dev)) {
>> - unsigned int max_segment;
>> -
>> - max_segment = swiotlb_max_segment();
>> - if (max_segment) {
>> - max_segment = max_t(unsigned int,
>> max_segment,
>> - PAGE_SIZE) >> PAGE_SHIFT;
>> - max_order = min(max_order,
>> ilog2(max_segment));
>> - }
>> + struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
>> + struct ttm_operation_ctx ctx = {
>> + .interruptible = true,
>> + .no_wait_gpu = false,
>> + };
>> + struct ttm_place place = {
>> + .fpfn = 0,
>> + .lpfn = 0,
>> + .mem_type = I915_PL_SYSTEM,
>> + .flags = 0,
>> + };
>> + struct ttm_placement placement = {
>> + .num_placement = 1,
>> + .placement = &place,
>> + .num_busy_placement = 0,
>> + .busy_placement = NULL,
>> + };
>> + int ret;
>> +
>> + ret = ttm_bo_validate(bo, &placement, &ctx);
>> + if (ret) {
>> + ret = i915_ttm_err_to_gem(ret);
>> + return ret;
>> }
>> -#endif
>>
>> - gfp = GFP_KERNEL | __GFP_HIGHMEM | __GFP_RECLAIMABLE;
>> - if (IS_I965GM(i915) || IS_I965G(i915)) {
>> - /* 965gm cannot relocate objects above 4GiB. */
>> - gfp &= ~__GFP_HIGHMEM;
>> - gfp |= __GFP_DMA32;
>
>
> It looks like we're losing this restriction?
>
> There is a flag to ttm_device_init() to make TTM only do __GFP_DMA32
> allocations.
agreed. will fix for v2
>
>> + if (bo->ttm && !ttm_tt_is_populated(bo->ttm)) {
>> + ret = ttm_tt_populate(bo->bdev, bo->ttm, &ctx);
>> + if (ret)
>> + return ret;
>> }
>>
>> -create_st:
>> - st = kmalloc(sizeof(*st), GFP_KERNEL);
>> - if (!st)
>> - return -ENOMEM;
>> + if (!i915_gem_object_has_pages(obj)) {
>> + struct i915_refct_sgt *rsgt =
>> + i915_ttm_resource_get_st(obj, bo->resource);
>>
>> - npages = obj->base.size / PAGE_SIZE;
>> - if (sg_alloc_table(st, npages, GFP_KERNEL)) {
>> - kfree(st);
>> - return -ENOMEM;
>> - }
>> + if (IS_ERR(rsgt))
>> + return PTR_ERR(rsgt);
>>
>> - sg = st->sgl;
>> - st->nents = 0;
>> - sg_page_sizes = 0;
>> -
>> - do {
>> - int order = min(fls(npages) - 1, max_order);
>> - struct page *page;
>> -
>> - do {
>> - page = alloc_pages(gfp | (order ? QUIET :
>> MAYFAIL),
>> - order);
>> - if (page)
>> - break;
>> - if (!order--)
>> - goto err;
>> -
>> - /* Limit subsequent allocations as well */
>> - max_order = order;
>> - } while (1);
>> -
>> - sg_set_page(sg, page, PAGE_SIZE << order, 0);
>> - sg_page_sizes |= PAGE_SIZE << order;
>> - st->nents++;
>> -
>> - npages -= 1 << order;
>> - if (!npages) {
>> - sg_mark_end(sg);
>> - break;
>> - }
>> -
>> - sg = __sg_next(sg);
>> - } while (1);
>> -
>> - if (i915_gem_gtt_prepare_pages(obj, st)) {
>> - /* Failed to dma-map try again with single page sg
>> segments */
>> - if (get_order(st->sgl->length)) {
>> - internal_free_pages(st);
>> - max_order = 0;
>> - goto create_st;
>> - }
>> - goto err;
>> + GEM_BUG_ON(obj->mm.rsgt);
>> + obj->mm.rsgt = rsgt;
>> + __i915_gem_object_set_pages(obj, &rsgt->table,
>> + i915_sg_dma_sizes(rsgt-
>>> table.sgl));
>> }
>>
>> - __i915_gem_object_set_pages(obj, st, sg_page_sizes);
>> + GEM_BUG_ON(bo->ttm && ((obj->base.size >> PAGE_SHIFT) < bo-
>>> ttm->num_pages));
>> + i915_ttm_adjust_lru(obj);
>>
>> return 0;
>> +}
>>
>> -err:
>> - sg_set_page(sg, NULL, 0, 0);
>> - sg_mark_end(sg);
>> - internal_free_pages(st);
>> +static const struct drm_i915_gem_object_ops
>> i915_gem_object_internal_ops = {
>> + .name = "i915_gem_object_ttm",
>> + .flags = I915_GEM_OBJECT_IS_SHRINKABLE,
>>
>> - return -ENOMEM;
>> -}
>> + .get_pages = i915_internal_get_pages,
>> + .put_pages = i915_ttm_put_pages,
>> + .adjust_lru = i915_ttm_adjust_lru,
>> + .delayed_free = i915_ttm_delayed_free,
>> +};
>>
>> -static void i915_gem_object_put_pages_internal(struct
>> drm_i915_gem_object *obj,
>> - struct sg_table
>> *pages)
>> +void i915_ttm_internal_bo_destroy(struct ttm_buffer_object *bo)
>> {
>> - i915_gem_gtt_finish_pages(obj, pages);
>> - internal_free_pages(pages);
>> + struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
>>
>> - obj->mm.dirty = false;
>> + mutex_destroy(&obj->ttm.get_io_page.lock);
>>
>> - __start_cpu_write(obj);
>> -}
>> + if (obj->ttm.created) {
>> + /* This releases all gem object bindings to the
>> backend. */
>> + __i915_gem_free_object(obj);
>>
>> -static const struct drm_i915_gem_object_ops
>> i915_gem_object_internal_ops = {
>> - .name = "i915_gem_object_internal",
>> - .flags = I915_GEM_OBJECT_IS_SHRINKABLE,
>> - .get_pages = i915_gem_object_get_pages_internal,
>> - .put_pages = i915_gem_object_put_pages_internal,
>> -};
>> + call_rcu(&obj->rcu, __i915_gem_free_object_rcu);
>> + } else {
>> + __i915_gem_object_fini(obj);
>> + }
>> +}
>>
>> +/**
>> + * i915_gem_object_create_internal: create an object with volatile
>> pages
>> + * @i915: the i915 device
>> + * @size: the size in bytes of backing storage to allocate for the
>> object
>> + *
>> + * Creates a new object that wraps some internal memory for private
>> use.
>> + * This object is not backed by swappable storage, and as such its
>> contents
>> + * are volatile and only valid whilst pinned. If the object is
>> reaped by the
>> + * shrinker, its pages and data will be discarded. Equally, it is
>> not a full
>> + * GEM object and so not valid for access from userspace. This makes
>> it useful
>> + * for hardware interfaces like ringbuffers (which are pinned from
>> the time
>> + * the request is written to the time the hardware stops accessing
>> it), but
>> + * not for contexts (which need to be preserved when not active for
>> later
>> + * reuse). Note that it is not cleared upon allocation.
>> + */
>> struct drm_i915_gem_object *
>> -__i915_gem_object_create_internal(struct drm_i915_private *i915,
>> - const struct
>> drm_i915_gem_object_ops *ops,
>> - phys_addr_t size)
>> +i915_gem_object_create_internal(struct drm_i915_private *i915,
>> + phys_addr_t size)
>> {
>> static struct lock_class_key lock_class;
>> struct drm_i915_gem_object *obj;
>> unsigned int cache_level;
>> + struct ttm_operation_ctx ctx = {
>> + .interruptible = true,
>> + .no_wait_gpu = false,
>> + };
>> + int ret;
>>
>> GEM_BUG_ON(!size);
>> GEM_BUG_ON(!IS_ALIGNED(size, PAGE_SIZE));
>> @@ -166,45 +129,34 @@ __i915_gem_object_create_internal(struct
>> drm_i915_private *i915,
>> return ERR_PTR(-ENOMEM);
>>
>> drm_gem_private_object_init(&i915->drm, &obj->base, size);
>> - i915_gem_object_init(obj, ops, &lock_class, 0);
>> - obj->mem_flags |= I915_BO_FLAG_STRUCT_PAGE;
>> + i915_gem_object_init(obj, &i915_gem_object_internal_ops,
>> &lock_class,
>> + I915_BO_ALLOC_VOLATILE);
>> +
>> + INIT_LIST_HEAD(&obj->mm.region_link);
>> +
>> + INIT_RADIX_TREE(&obj->ttm.get_io_page.radix, GFP_KERNEL |
>> __GFP_NOWARN);
>> + mutex_init(&obj->ttm.get_io_page.lock);
>>
>> - /*
>> - * Mark the object as volatile, such that the pages are
>> marked as
>> - * dontneed whilst they are still pinned. As soon as they are
>> unpinned
>> - * they are allowed to be reaped by the shrinker, and the
>> caller is
>> - * expected to repopulate - the contents of this object are
>> only valid
>> - * whilst active and pinned.
>> - */
>> - i915_gem_object_set_volatile(obj);
>> + obj->base.vma_node.driver_private = i915_gem_to_ttm(obj);
>>
>> + ret = ttm_bo_init_reserved(&i915->bdev, i915_gem_to_ttm(obj),
>> size,
>> + ttm_bo_type_kernel,
>> i915_ttm_sys_placement(),
>> + 0, &ctx, NULL, NULL,
>> i915_ttm_internal_bo_destroy);
>> + if (ret) {
>> + ret = i915_ttm_err_to_gem(ret);
>> + i915_gem_object_free(obj);
>> + return ERR_PTR(ret);
>> + }
>> +
>> + obj->ttm.created = true;
>> obj->read_domains = I915_GEM_DOMAIN_CPU;
>> obj->write_domain = I915_GEM_DOMAIN_CPU;
>> -
>> + obj->mem_flags &= ~I915_BO_FLAG_IOMEM;
>> + obj->mem_flags |= I915_BO_FLAG_STRUCT_PAGE;
>> cache_level = HAS_LLC(i915) ? I915_CACHE_LLC :
>> I915_CACHE_NONE;
>> i915_gem_object_set_cache_coherency(obj, cache_level);
>> + i915_gem_object_unlock(obj);
>>
>> return obj;
>> }
>>
>> -/**
>> - * i915_gem_object_create_internal: create an object with volatile
>> pages
>> - * @i915: the i915 device
>> - * @size: the size in bytes of backing storage to allocate for the
>> object
>> - *
>> - * Creates a new object that wraps some internal memory for private
>> use.
>> - * This object is not backed by swappable storage, and as such its
>> contents
>> - * are volatile and only valid whilst pinned. If the object is
>> reaped by the
>> - * shrinker, its pages and data will be discarded. Equally, it is
>> not a full
>> - * GEM object and so not valid for access from userspace. This makes
>> it useful
>> - * for hardware interfaces like ringbuffers (which are pinned from
>> the time
>> - * the request is written to the time the hardware stops accessing
>> it), but
>> - * not for contexts (which need to be preserved when not active for
>> later
>> - * reuse). Note that it is not cleared upon allocation.
>> - */
>> -struct drm_i915_gem_object *
>> -i915_gem_object_create_internal(struct drm_i915_private *i915,
>> - phys_addr_t size)
>> -{
>> - return __i915_gem_object_create_internal(i915,
>> &i915_gem_object_internal_ops, size);
>
> While we don't have a TTM shmem backend ready yet for internal,
>
> Did you consider setting up just yet another region,
> INTEL_REGION_INTERNAL,
> .class = INTEL_MEMORY_SYSTEM and
> .instance = 1,
>
> And make it create a TTM system region on integrated, and use
> same region as INTEL_REGION_SMEM on dgfx.
>
> I think ttm should automatically map that to I915_PL_SYSTEM and the
> backwards mapping in i915_ttm_region() should never get called since
> the object is never moved.
>
> Then I figure it should suffice to just call
> __i915_gem_ttm_object_init() and we could drop a lot of code.
>
i briefly considered using a new fake region, but with current precedent
mapping memory regions to real segemented memory areas I considered it
an abuse of the semantics of memory regions.
If we are happy to have fake regions, I can revert it back to a previous
design of using system region for discreet and add a fake region setup
for integrated.
Would this be preferred over the current design?
> /Thomas
>
>
>
>
>> -}
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_internal.h
>> b/drivers/gpu/drm/i915/gem/i915_gem_internal.h
>> index 6664e06112fc..524e1042b20f 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_internal.h
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_internal.h
>> @@ -15,9 +15,4 @@ struct drm_i915_private;
>> struct drm_i915_gem_object *
>> i915_gem_object_create_internal(struct drm_i915_private *i915,
>> phys_addr_t size);
>> -struct drm_i915_gem_object *
>> -__i915_gem_object_create_internal(struct drm_i915_private *i915,
>> - const struct
>> drm_i915_gem_object_ops *ops,
>> - phys_addr_t size);
>> -
>> #endif /* __I915_GEM_INTERNAL_H__ */
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
>> b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
>> index fdb3a1c18cb6..92195ead8c11 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
>> @@ -83,7 +83,7 @@ struct ttm_placement *i915_ttm_sys_placement(void)
>> return &i915_sys_placement;
>> }
>>
>> -static int i915_ttm_err_to_gem(int err)
>> +int i915_ttm_err_to_gem(int err)
>> {
>> /* Fastpath */
>> if (likely(!err))
>> @@ -745,8 +745,8 @@ struct ttm_device_funcs *i915_ttm_driver(void)
>> return &i915_ttm_bo_driver;
>> }
>>
>> -static int __i915_ttm_get_pages(struct drm_i915_gem_object *obj,
>> - struct ttm_placement *placement)
>> +int __i915_ttm_get_pages(struct drm_i915_gem_object *obj,
>> + struct ttm_placement *placement)
>> {
>> struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
>> struct ttm_operation_ctx ctx = {
>> @@ -871,8 +871,8 @@ static int i915_ttm_migrate(struct
>> drm_i915_gem_object *obj,
>> return __i915_ttm_migrate(obj, mr, obj->flags);
>> }
>>
>> -static void i915_ttm_put_pages(struct drm_i915_gem_object *obj,
>> - struct sg_table *st)
>> +void i915_ttm_put_pages(struct drm_i915_gem_object *obj,
>> + struct sg_table *st)
>> {
>> /*
>> * We're currently not called from a shrinker, so put_pages()
>> @@ -995,7 +995,7 @@ void i915_ttm_adjust_lru(struct
>> drm_i915_gem_object *obj)
>> * it's not idle, and using the TTM destroyed list handling could
>> help us
>> * benefit from that.
>> */
>> -static void i915_ttm_delayed_free(struct drm_i915_gem_object *obj)
>> +void i915_ttm_delayed_free(struct drm_i915_gem_object *obj)
>> {
>> GEM_BUG_ON(!obj->ttm.created);
>>
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.h
>> b/drivers/gpu/drm/i915/gem/i915_gem_ttm.h
>> index 73e371aa3850..06701c46d8e2 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.h
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.h
>> @@ -26,6 +26,7 @@ i915_gem_to_ttm(struct drm_i915_gem_object *obj)
>> * i915 ttm gem object destructor. Internal use only.
>> */
>> void i915_ttm_bo_destroy(struct ttm_buffer_object *bo);
>> +void i915_ttm_internal_bo_destroy(struct ttm_buffer_object *bo);
>>
>> /**
>> * i915_ttm_to_gem - Convert a struct ttm_buffer_object to an
>> embedding
>> @@ -37,8 +38,10 @@ void i915_ttm_bo_destroy(struct ttm_buffer_object
>> *bo);
>> static inline struct drm_i915_gem_object *
>> i915_ttm_to_gem(struct ttm_buffer_object *bo)
>> {
>> - if (bo->destroy != i915_ttm_bo_destroy)
>> + if (bo->destroy != i915_ttm_bo_destroy &&
>> + bo->destroy != i915_ttm_internal_bo_destroy) {
>> return NULL;
>> + }
>>
>> return container_of(bo, struct drm_i915_gem_object,
>> __do_not_access);
>> }
>> @@ -66,6 +69,7 @@ i915_ttm_resource_get_st(struct drm_i915_gem_object
>> *obj,
>> struct ttm_resource *res);
>>
>> void i915_ttm_adjust_lru(struct drm_i915_gem_object *obj);
>> +void i915_ttm_delayed_free(struct drm_i915_gem_object *obj);
>>
>> int i915_ttm_purge(struct drm_i915_gem_object *obj);
>>
>> @@ -92,4 +96,10 @@ static inline bool i915_ttm_cpu_maps_iomem(struct
>> ttm_resource *mem)
>> /* Once / if we support GGTT, this is also false for cached
>> ttm_tts */
>> return mem->mem_type != I915_PL_SYSTEM;
>> }
>> +
>> +int __i915_ttm_get_pages(struct drm_i915_gem_object *obj,
>> + struct ttm_placement *placement);
>> +void i915_ttm_put_pages(struct drm_i915_gem_object *obj, struct
>> sg_table *st);
>> +int i915_ttm_err_to_gem(int err);
>> +
>> #endif
>
>
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