[PATCH 4/5] drm/panfrost: Add support for GPU heap allocations
Steven Price
steven.price at arm.com
Thu Jul 18 15:03:44 UTC 2019
On 17/07/2019 19:33, Rob Herring wrote:
> The midgard/bifrost GPUs need to allocate GPU heap memory which is
> allocated on GPU page faults and not pinned in memory. The vendor driver
> calls this functionality GROW_ON_GPF.
>
> This implementation assumes that BOs allocated with the
> PANFROST_BO_NOEXEC flag are never mmapped or exported. Both of those may
> actually work, but I'm unsure if there's some interaction there. It
> would cause the whole object to be pinned in memory which would defeat
> the point of this.
>
> On faults, we map in 2MB at a time in order to utilize huge pages (if
> enabled). Currently, once we've mapped pages in, they are only unmapped
> if the BO is freed. Once we add shrinker support, we can unmap pages
> with the shrinker.
>
> Cc: Tomeu Vizoso <tomeu.vizoso at collabora.com>
> Cc: Boris Brezillon <boris.brezillon at collabora.com>
> Cc: Robin Murphy <robin.murphy at arm.com>
> Cc: Steven Price <steven.price at arm.com>
> Cc: Alyssa Rosenzweig <alyssa at rosenzweig.io>
> Signed-off-by: Rob Herring <robh at kernel.org>
> ---
> drivers/gpu/drm/panfrost/TODO | 2 -
> drivers/gpu/drm/panfrost/panfrost_drv.c | 2 +-
> drivers/gpu/drm/panfrost/panfrost_gem.c | 14 ++-
> drivers/gpu/drm/panfrost/panfrost_gem.h | 8 ++
> drivers/gpu/drm/panfrost/panfrost_mmu.c | 114 +++++++++++++++++++++---
> include/uapi/drm/panfrost_drm.h | 1 +
> 6 files changed, 125 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/panfrost/TODO b/drivers/gpu/drm/panfrost/TODO
> index c2e44add37d8..64129bf73933 100644
> --- a/drivers/gpu/drm/panfrost/TODO
> +++ b/drivers/gpu/drm/panfrost/TODO
> @@ -14,8 +14,6 @@
> The hard part is handling when more address spaces are needed than what
> the h/w provides.
>
> -- Support pinning pages on demand (GPU page faults).
> -
> - Support userspace controlled GPU virtual addresses. Needed for Vulkan. (Tomeu)
>
> - Support for madvise and a shrinker.
> diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
> index b91e991bc6a3..9e87d0060202 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_drv.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
> @@ -50,7 +50,7 @@ static int panfrost_ioctl_create_bo(struct drm_device *dev, void *data,
> struct drm_panfrost_create_bo *args = data;
>
> if (!args->size || args->pad ||
> - (args->flags & ~PANFROST_BO_NOEXEC))
> + (args->flags & ~(PANFROST_BO_NOEXEC | PANFROST_BO_HEAP)))
> return -EINVAL;
>
> bo = panfrost_gem_create_with_handle(file, dev, args->size, args->flags,
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
> index 37ffec8391da..528396000038 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gem.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
> @@ -87,7 +87,10 @@ static int panfrost_gem_map(struct panfrost_device *pfdev, struct panfrost_gem_o
> if (ret)
> return ret;
>
> - return panfrost_mmu_map(bo);
> + if (!bo->is_heap)
> + ret = panfrost_mmu_map(bo);
> +
> + return ret;
> }
>
> struct panfrost_gem_object *
> @@ -101,7 +104,11 @@ panfrost_gem_create_with_handle(struct drm_file *file_priv,
> struct drm_gem_shmem_object *shmem;
> struct panfrost_gem_object *bo;
>
> - size = roundup(size, PAGE_SIZE);
> + /* Round up heap allocations to 2MB to keep fault handling simple */
> + if (flags & PANFROST_BO_HEAP)
> + size = roundup(size, SZ_2M);
> + else
> + size = roundup(size, PAGE_SIZE);
>
> shmem = drm_gem_shmem_create_with_handle(file_priv, dev, size, handle);
> if (IS_ERR(shmem))
> @@ -109,6 +116,9 @@ panfrost_gem_create_with_handle(struct drm_file *file_priv,
>
> bo = to_panfrost_bo(&shmem->base);
> bo->noexec = !!(flags & PANFROST_BO_NOEXEC);
> + bo->is_heap = !!(flags & PANFROST_BO_HEAP);
> + if (bo->is_heap)
> + bo->noexec = true;
While I agree an executable heap is pretty weird, I'd prefer making this
explicit - i.e. failing the allocation if the flags don't make sense.
>
> ret = panfrost_gem_map(pfdev, bo);
> if (ret)
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.h b/drivers/gpu/drm/panfrost/panfrost_gem.h
> index 132f02399b7b..c500ca6b9072 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gem.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.h
> @@ -13,6 +13,7 @@ struct panfrost_gem_object {
> struct drm_mm_node node;
> bool is_mapped :1;
> bool noexec :1;
> + bool is_heap :1;
> };
>
> static inline
> @@ -21,6 +22,13 @@ struct panfrost_gem_object *to_panfrost_bo(struct drm_gem_object *obj)
> return container_of(to_drm_gem_shmem_obj(obj), struct panfrost_gem_object, base);
> }
>
> +static inline
> +struct panfrost_gem_object *drm_mm_node_to_panfrost_bo(struct drm_mm_node *node)
> +{
> + return container_of(node, struct panfrost_gem_object, node);
> +}
> +
> +
NIT: Extra blank line
> struct drm_gem_object *panfrost_gem_create_object(struct drm_device *dev, size_t size);
>
> struct panfrost_gem_object *
> diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> index d18484a07bfa..3b95c7027188 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> @@ -3,6 +3,7 @@
> /* Copyright (C) 2019 Arm Ltd. */
> #include <linux/bitfield.h>
> #include <linux/delay.h>
> +#include <linux/dma-mapping.h>
> #include <linux/interrupt.h>
> #include <linux/io.h>
> #include <linux/iopoll.h>
> @@ -10,6 +11,7 @@
> #include <linux/iommu.h>
> #include <linux/platform_device.h>
> #include <linux/pm_runtime.h>
> +#include <linux/shmem_fs.h>
> #include <linux/sizes.h>
>
> #include "panfrost_device.h"
> @@ -257,12 +259,12 @@ void panfrost_mmu_unmap(struct panfrost_gem_object *bo)
> size_t unmapped_page;
> size_t pgsize = get_pgsize(iova, len - unmapped_len);
>
> - unmapped_page = ops->unmap(ops, iova, pgsize);
> - if (!unmapped_page)
> - break;
> -
> - iova += unmapped_page;
> - unmapped_len += unmapped_page;
> + if (ops->iova_to_phys(ops, iova)) {
> + unmapped_page = ops->unmap(ops, iova, pgsize);
> + WARN_ON(unmapped_page != pgsize);
> + }
> + iova += pgsize;
> + unmapped_len += pgsize;
> }
>
> mmu_hw_do_operation(pfdev, 0, bo->node.start << PAGE_SHIFT,
> @@ -298,6 +300,86 @@ static const struct iommu_gather_ops mmu_tlb_ops = {
> .tlb_sync = mmu_tlb_sync_context,
> };
>
> +static struct drm_mm_node *addr_to_drm_mm_node(struct panfrost_device *pfdev, int as, u64 addr)
> +{
> + struct drm_mm_node *node;
> + u64 offset = addr >> PAGE_SHIFT;
> +
> + drm_mm_for_each_node(node, &pfdev->mm) {
> + if (offset >= node->start && offset < (node->start + node->size))
> + return node;
> + }
> + return NULL;
> +}
> +
> +#define NUM_FAULT_PAGES (SZ_2M / PAGE_SIZE)
> +
> +int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as, u64 addr)
> +{
> + int ret, i;
> + struct drm_mm_node *node;
> + struct panfrost_gem_object *bo;
> + struct address_space *mapping;
> + pgoff_t page_offset;
> + struct sg_table sgt = {};
> + struct page **pages;
> +
> + node = addr_to_drm_mm_node(pfdev, as, addr);
> + if (!node)
> + return -ENOENT;
> +
> + bo = drm_mm_node_to_panfrost_bo(node);
> + if (!bo->is_heap) {
> + dev_WARN(pfdev->dev, "matching BO is not heap type (GPU VA = %llx)",
> + node->start << PAGE_SHIFT);
> + return -EINVAL;
> + }
> + /* Assume 2MB alignment and size multiple */
> + addr &= ~((u64)SZ_2M - 1);
> + page_offset = addr >> PAGE_SHIFT;
> + page_offset -= node->start;
> +
> + pages = kvmalloc_array(NUM_FAULT_PAGES, sizeof(struct page *), GFP_KERNEL);
> + if (!pages)
> + return -ENOMEM;
> +
> + mapping = bo->base.base.filp->f_mapping;
> + mapping_set_unevictable(mapping);
> +
> + for (i = 0; i < NUM_FAULT_PAGES; i++) {
> + pages[i] = shmem_read_mapping_page(mapping, page_offset + i);
> + if (IS_ERR(pages[i])) {
> + ret = PTR_ERR(pages[i]);
> + goto err_pages;
> + }
> + }
> +
> + ret = sg_alloc_table_from_pages(&sgt, pages, NUM_FAULT_PAGES, 0,
> + SZ_2M, GFP_KERNEL);
> + if (ret)
> + goto err_pages;
> +
> + if (dma_map_sg(pfdev->dev, sgt.sgl, sgt.nents, DMA_BIDIRECTIONAL) == 0) {
> + ret = -EINVAL;
> + goto err_map;
> + }
> +
> + mmu_map_sg(pfdev, addr, IOMMU_WRITE | IOMMU_READ | IOMMU_NOEXEC, &sgt);
> +
> + mmu_write(pfdev, MMU_INT_CLEAR, BIT(as));
> + bo->is_mapped = true;
> +
> + dev_dbg(pfdev->dev, "mapped page fault @ %llx", addr);
> +
> + return 0;
You still need to free sgt and pages - so this should be:
ret = 0;
to fall through to the clean up below:
> +
> +err_map:
> + sg_free_table(&sgt);
> +err_pages:
> + kvfree(pages);
> + return ret;
> +}
> +
But actually, you need to store the pages allocated in the buffer object
so that they can be freed later. At the moment you have a big memory leak.
> static const char *access_type_name(struct panfrost_device *pfdev,
> u32 fault_status)
> {
> @@ -323,13 +405,11 @@ static irqreturn_t panfrost_mmu_irq_handler(int irq, void *data)
> {
> struct panfrost_device *pfdev = data;
> u32 status = mmu_read(pfdev, MMU_INT_STAT);
> - int i;
> + int i, ret;
>
> if (!status)
> return IRQ_NONE;
>
> - dev_err(pfdev->dev, "mmu irq status=%x\n", status);
> -
> for (i = 0; status; i++) {
> u32 mask = BIT(i) | BIT(i + 16);
> u64 addr;
> @@ -350,6 +430,17 @@ static irqreturn_t panfrost_mmu_irq_handler(int irq, void *data)
> access_type = (fault_status >> 8) & 0x3;
> source_id = (fault_status >> 16);
>
> + /* Page fault only */
> + if ((status & mask) == BIT(i)) {
> + WARN_ON(exception_type < 0xC1 || exception_type > 0xC4);
> +
> + ret = panfrost_mmu_map_fault_addr(pfdev, i, addr);
> + if (!ret) {
> + status &= ~mask;
> + continue;
In this case the IRQ isn't handled and will remain asserted, which
probably isn't going to end particularly well.
Ideally you would switch the address space to UNMAPPED to kill off the
job, but at the very least we should acknowledge the interrupt and let
the GPU timeout reset the GPU to recover (which is equivalent while we
still only use the one AS on the GPU).
Steve
> + }
> + }
> +
> /* terminal fault, print info about the fault */
> dev_err(pfdev->dev,
> "Unhandled Page fault in AS%d at VA 0x%016llX\n"
> @@ -391,8 +482,9 @@ int panfrost_mmu_init(struct panfrost_device *pfdev)
> if (irq <= 0)
> return -ENODEV;
>
> - err = devm_request_irq(pfdev->dev, irq, panfrost_mmu_irq_handler,
> - IRQF_SHARED, "mmu", pfdev);
> + err = devm_request_threaded_irq(pfdev->dev, irq, NULL,
> + panfrost_mmu_irq_handler,
> + IRQF_ONESHOT, "mmu", pfdev);
>
> if (err) {
> dev_err(pfdev->dev, "failed to request mmu irq");
> diff --git a/include/uapi/drm/panfrost_drm.h b/include/uapi/drm/panfrost_drm.h
> index 17fb5d200f7a..9150dd75aad8 100644
> --- a/include/uapi/drm/panfrost_drm.h
> +++ b/include/uapi/drm/panfrost_drm.h
> @@ -83,6 +83,7 @@ struct drm_panfrost_wait_bo {
> };
>
> #define PANFROST_BO_NOEXEC 1
> +#define PANFROST_BO_HEAP 2
>
> /**
> * struct drm_panfrost_create_bo - ioctl argument for creating Panfrost BOs.
>
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