drm/panfrost: Add support for GPU heap allocations

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@collabora.com>
Cc: Boris Brezillon <boris.brezillon@collabora.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Acked-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190808222200.13176-9-robh@kernel.org

drivers/gpu/drm/panfrost/TODO

@@ -10,8 +10,6 @@
   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)
 
 - Compute job support. So called 'compute only' jobs need to be plumbed up to

drivers/gpu/drm/panfrost/panfrost_drv.c

@@ -82,7 +82,12 @@ 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;
+
+	/* Heaps should never be executable */
+	if ((args->flags & PANFROST_BO_HEAP) &&
+	    !(args->flags & PANFROST_BO_NOEXEC))
 		return -EINVAL;
 
 	bo = panfrost_gem_create_with_handle(file, dev, args->size, args->flags,
@@ -297,6 +302,10 @@ static int panfrost_ioctl_mmap_bo(struct drm_device *dev, void *data,
 		return -ENOENT;
 	}
 
+	/* Don't allow mmapping of heap objects as pages are not pinned. */
+	if (to_panfrost_bo(gem_obj)->is_heap)
+		return -EINVAL;
+
 	ret = drm_gem_create_mmap_offset(gem_obj);
 	if (ret == 0)
 		args->offset = drm_vma_node_offset_addr(&gem_obj->vma_node);

drivers/gpu/drm/panfrost/panfrost_gem.c

@@ -19,6 +19,20 @@ static void panfrost_gem_free_object(struct drm_gem_object *obj)
 	struct panfrost_gem_object *bo = to_panfrost_bo(obj);
 	struct panfrost_device *pfdev = obj->dev->dev_private;
 
+	if (bo->sgts) {
+		int i;
+		int n_sgt = bo->base.base.size / SZ_2M;
+
+		for (i = 0; i < n_sgt; i++) {
+			if (bo->sgts[i].sgl) {
+				dma_unmap_sg(pfdev->dev, bo->sgts[i].sgl,
+					     bo->sgts[i].nents, DMA_BIDIRECTIONAL);
+				sg_free_table(&bo->sgts[i]);
+			}
+		}
+		kfree(bo->sgts);
+	}
+
 	mutex_lock(&pfdev->shrinker_lock);
 	if (!list_empty(&bo->base.madv_list))
 		list_del(&bo->base.madv_list);
@@ -53,10 +67,11 @@ static int panfrost_gem_open(struct drm_gem_object *obj, struct drm_file *file_p
 	if (ret)
 		goto out;
 
+	if (!bo->is_heap) {
 		ret = panfrost_mmu_map(bo);
 		if (ret)
 			drm_mm_remove_node(&bo->node);
-
+	}
 out:
 	spin_unlock(&pfdev->mm_lock);
 	return ret;
@@ -76,12 +91,20 @@ static void panfrost_gem_close(struct drm_gem_object *obj, struct drm_file *file
 	spin_unlock(&pfdev->mm_lock);
 }
 
+static int panfrost_gem_pin(struct drm_gem_object *obj)
+{
+	if (to_panfrost_bo(obj)->is_heap)
+		return -EINVAL;
+
+	return drm_gem_shmem_pin(obj);
+}
+
 static const struct drm_gem_object_funcs panfrost_gem_funcs = {
 	.free = panfrost_gem_free_object,
 	.open = panfrost_gem_open,
 	.close = panfrost_gem_close,
 	.print_info = drm_gem_shmem_print_info,
-	.pin = drm_gem_shmem_pin,
+	.pin = panfrost_gem_pin,
 	.unpin = drm_gem_shmem_unpin,
 	.get_sg_table = drm_gem_shmem_get_sg_table,
 	.vmap = drm_gem_shmem_vmap,
@@ -120,12 +143,17 @@ panfrost_gem_create_with_handle(struct drm_file *file_priv,
 	struct drm_gem_shmem_object *shmem;
 	struct panfrost_gem_object *bo;
 
+	/* Round up heap allocations to 2MB to keep fault handling simple */
+	if (flags & PANFROST_BO_HEAP)
+		size = roundup(size, SZ_2M);
+
 	shmem = drm_gem_shmem_create(dev, size);
 	if (IS_ERR(shmem))
 		return ERR_CAST(shmem);
 
 	bo = to_panfrost_bo(&shmem->base);
 	bo->noexec = !!(flags & PANFROST_BO_NOEXEC);
+	bo->is_heap = !!(flags & PANFROST_BO_HEAP);
 
 	/*
 	 * Allocate an id of idr table where the obj is registered

drivers/gpu/drm/panfrost/panfrost_gem.h

@@ -9,10 +9,12 @@
 
 struct panfrost_gem_object {
 	struct drm_gem_shmem_object base;
+	struct sg_table *sgts;
 
 	struct drm_mm_node node;
 	bool is_mapped		:1;
 	bool noexec		:1;
+	bool is_heap		:1;
 };
 
 static inline
@@ -21,6 +23,12 @@ 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);
+}
+
 struct drm_gem_object *panfrost_gem_create_object(struct drm_device *dev, size_t size);
 
 struct drm_gem_object *

drivers/gpu/drm/panfrost/panfrost_mmu.c

@@ -2,6 +2,7 @@
 /* Copyright 2019 Linaro, Ltd, Rob Herring <robh@kernel.org> */
 #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>
@@ -9,6 +10,7 @@
 #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"
@@ -240,12 +242,12 @@ void panfrost_mmu_unmap(struct panfrost_gem_object *bo)
 		size_t unmapped_page;
 		size_t pgsize = get_pgsize(iova, len - unmapped_len);
 
+		if (ops->iova_to_phys(ops, iova)) {
 			unmapped_page = ops->unmap(ops, iova, pgsize);
-		if (!unmapped_page)
-			break;
-
-		iova += unmapped_page;
-		unmapped_len += unmapped_page;
+			WARN_ON(unmapped_page != pgsize);
+		}
+		iova += pgsize;
+		unmapped_len += pgsize;
 	}
 
 	mmu_hw_do_operation(pfdev, 0, bo->node.start << PAGE_SHIFT,
@@ -281,6 +283,105 @@ 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;
+
+	mutex_lock(&bo->base.pages_lock);
+
+	if (!bo->base.pages) {
+		bo->sgts = kvmalloc_array(bo->base.base.size / SZ_2M,
+				     sizeof(struct sg_table), GFP_KERNEL | __GFP_ZERO);
+		if (!bo->sgts)
+			return -ENOMEM;
+
+		pages = kvmalloc_array(bo->base.base.size >> PAGE_SHIFT,
+				       sizeof(struct page *), GFP_KERNEL | __GFP_ZERO);
+		if (!pages) {
+			kfree(bo->sgts);
+			bo->sgts = NULL;
+			return -ENOMEM;
+		}
+		bo->base.pages = pages;
+		bo->base.pages_use_count = 1;
+	} else
+		pages = bo->base.pages;
+
+	mapping = bo->base.base.filp->f_mapping;
+	mapping_set_unevictable(mapping);
+
+	for (i = page_offset; i < page_offset + NUM_FAULT_PAGES; i++) {
+		pages[i] = shmem_read_mapping_page(mapping, i);
+		if (IS_ERR(pages[i])) {
+			mutex_unlock(&bo->base.pages_lock);
+			ret = PTR_ERR(pages[i]);
+			goto err_pages;
+		}
+	}
+
+	mutex_unlock(&bo->base.pages_lock);
+
+	sgt = &bo->sgts[page_offset / (SZ_2M / PAGE_SIZE)];
+	ret = sg_alloc_table_from_pages(sgt, pages + page_offset,
+					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)) {
+		ret = -EINVAL;
+		goto err_map;
+	}
+
+	mmu_map_sg(pfdev, addr, IOMMU_WRITE | IOMMU_READ | IOMMU_NOEXEC, sgt);
+
+	bo->is_mapped = true;
+
+	dev_dbg(pfdev->dev, "mapped page fault @ %llx", addr);
+
+	return 0;
+
+err_map:
+	sg_free_table(sgt);
+err_pages:
+	drm_gem_shmem_put_pages(&bo->base);
+	return ret;
+}
+
 static const char *access_type_name(struct panfrost_device *pfdev,
 		u32 fault_status)
 {
@@ -317,9 +418,7 @@ static irqreturn_t panfrost_mmu_irq_handler_thread(int irq, void *data)
 {
 	struct panfrost_device *pfdev = data;
 	u32 status = mmu_read(pfdev, MMU_INT_RAWSTAT);
-	int i;
-
-	dev_err(pfdev->dev, "mmu irq status=%x\n", status);
+	int i, ret;
 
 	for (i = 0; status; i++) {
 		u32 mask = BIT(i) | BIT(i + 16);
@@ -341,6 +440,18 @@ static irqreturn_t panfrost_mmu_irq_handler_thread(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) {
+				mmu_write(pfdev, MMU_INT_CLEAR, BIT(i));
+				status &= ~mask;
+				continue;
+			}
+		}
+
 		/* terminal fault, print info about the fault */
 		dev_err(pfdev->dev,
 			"Unhandled Page fault in AS%d at VA 0x%016llX\n"

include/uapi/drm/panfrost_drm.h

@@ -85,6 +85,7 @@ 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.