linux-kernel - [PATCH v18 15/26] drm/panfrost: Explicitly get and put drm-shmem pages

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Message-ID: <20231029230205.93277-16-dmitry.osipenko@collabora.com>
Date:   Mon, 30 Oct 2023 02:01:54 +0300
From:   Dmitry Osipenko <dmitry.osipenko@...labora.com>
To:     David Airlie <airlied@...il.com>,
        Gerd Hoffmann <kraxel@...hat.com>,
        Gurchetan Singh <gurchetansingh@...omium.org>,
        Chia-I Wu <olvaffe@...il.com>, Daniel Vetter <daniel@...ll.ch>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Christian König <christian.koenig@....com>,
        Qiang Yu <yuq825@...il.com>,
        Steven Price <steven.price@....com>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Emma Anholt <emma@...olt.net>, Melissa Wen <mwen@...lia.com>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        kernel@...labora.com, virtualization@...ts.linux-foundation.org
Subject: [PATCH v18 15/26] drm/panfrost: Explicitly get and put drm-shmem pages

To simplify the drm-shmem refcnt handling, we're moving away from
the implicit get_pages() that is used by get_pages_sgt(). From now on
drivers will have to pin pages while they use sgt. Panfrost's shrinker
doesn't support swapping out BOs, hence pages are pinned and sgt is valid
as long as pages' use-count > 0.

Signed-off-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>
---
 drivers/gpu/drm/panfrost/panfrost_gem.c | 17 +++++++++++++++++
 drivers/gpu/drm/panfrost/panfrost_mmu.c |  6 ++----
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
index 6b77d8cebcb2..bb9d43cf7c3c 100644
--- a/drivers/gpu/drm/panfrost/panfrost_gem.c
+++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
@@ -47,8 +47,13 @@ static void panfrost_gem_free_object(struct drm_gem_object *obj)
 			}
 		}
 		kvfree(bo->sgts);
+
+		drm_gem_shmem_put_pages(&bo->base);
 	}
 
+	if (!bo->is_heap && !obj->import_attach)
+		drm_gem_shmem_put_pages(&bo->base);
+
 	drm_gem_shmem_free(&bo->base);
 }
 
@@ -269,6 +274,7 @@ panfrost_gem_create(struct drm_device *dev, size_t size, u32 flags)
 {
 	struct drm_gem_shmem_object *shmem;
 	struct panfrost_gem_object *bo;
+	int err;
 
 	/* Round up heap allocations to 2MB to keep fault handling simple */
 	if (flags & PANFROST_BO_HEAP)
@@ -282,7 +288,18 @@ panfrost_gem_create(struct drm_device *dev, size_t size, u32 flags)
 	bo->noexec = !!(flags & PANFROST_BO_NOEXEC);
 	bo->is_heap = !!(flags & PANFROST_BO_HEAP);
 
+	if (!bo->is_heap) {
+		err = drm_gem_shmem_get_pages(shmem);
+		if (err)
+			goto err_free;
+	}
+
 	return bo;
+
+err_free:
+	drm_gem_shmem_free(&bo->base);
+
+	return ERR_PTR(err);
 }
 
 struct drm_gem_object *
diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
index 770dab1942c2..ac145a98377b 100644
--- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
+++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
@@ -504,7 +504,7 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
 		if (IS_ERR(pages[i])) {
 			ret = PTR_ERR(pages[i]);
 			pages[i] = NULL;
-			goto err_pages;
+			goto err_unlock;
 		}
 	}
 
@@ -512,7 +512,7 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
 	ret = sg_alloc_table_from_pages(sgt, pages + page_offset,
 					NUM_FAULT_PAGES, 0, SZ_2M, GFP_KERNEL);
 	if (ret)
-		goto err_pages;
+		goto err_unlock;
 
 	ret = dma_map_sgtable(pfdev->dev, sgt, DMA_BIDIRECTIONAL, 0);
 	if (ret)
@@ -535,8 +535,6 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
 
 err_map:
 	sg_free_table(sgt);
-err_pages:
-	drm_gem_shmem_put_pages_locked(&bo->base);
 err_unlock:
 	dma_resv_unlock(obj->resv);
 err_bo:
-- 
2.41.0