[PATCH 6/8] drm/panfrost: Make sure imported/exported BOs are never purged

[Boris Brezillon]

We don't want imported/exported BOs to be purges, as those are shared
with other processes that might still use them. We should also refuse
to export a BO if it's been marked purgeable or has already been purged.

Fixes: 013b65101315 ("drm/panfrost: Add madvise and shrinker support")
Cc: <sta...@vger.kernel.org>
Signed-off-by: Boris Brezillon <boris.brezil...@collabora.com>
---
 drivers/gpu/drm/panfrost/panfrost_drv.c | 19 ++++++++++++++++-
 drivers/gpu/drm/panfrost/panfrost_gem.c | 27 +++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c 
b/drivers/gpu/drm/panfrost/panfrost_drv.c
index 1c67ac434e10..751df975534f 100644
--- a/drivers/gpu/drm/panfrost/panfrost_drv.c
+++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
@@ -343,6 +343,7 @@ static int panfrost_ioctl_madvise(struct drm_device *dev, 
void *data,
        struct drm_panfrost_madvise *args = data;
        struct panfrost_device *pfdev = dev->dev_private;
        struct drm_gem_object *gem_obj;
+       int ret;
 
        gem_obj = drm_gem_object_lookup(file_priv, args->handle);
        if (!gem_obj) {
@@ -350,6 +351,19 @@ static int panfrost_ioctl_madvise(struct drm_device *dev, 
void *data,
                return -ENOENT;
        }
 
+       /*
+        * We don't want to mark exported/imported BOs as purgeable: we're not
+        * the only owner in that case.
+        */
+       mutex_lock(&dev->object_name_lock);
+       if (gem_obj->dma_buf)
+               ret = -EINVAL;
+       else
+               ret = 0;
+
+       if (ret)
+               goto out_unlock_object_name;
+
        mutex_lock(&pfdev->shrinker_lock);
        args->retained = drm_gem_shmem_madvise(gem_obj, args->madv);
 
@@ -364,8 +378,11 @@ static int panfrost_ioctl_madvise(struct drm_device *dev, 
void *data,
        }
        mutex_unlock(&pfdev->shrinker_lock);
 
+out_unlock_object_name:
+       mutex_unlock(&dev->object_name_lock);
+
        drm_gem_object_put_unlocked(gem_obj);
-       return 0;
+       return ret;
 }
 
 int panfrost_unstable_ioctl_check(void)
diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c 
b/drivers/gpu/drm/panfrost/panfrost_gem.c
index 92a95210a899..31d6417dd21c 100644
--- a/drivers/gpu/drm/panfrost/panfrost_gem.c
+++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
@@ -99,6 +99,32 @@ void panfrost_gem_close(struct drm_gem_object *obj, struct 
drm_file *file_priv)
        spin_unlock(&priv->mm_lock);
 }
 
+static struct dma_buf *
+panfrost_gem_export(struct drm_gem_object *obj, int flags)
+{
+       struct panfrost_gem_object *bo = to_panfrost_bo(obj);
+       int ret;
+
+       /*
+        * We must make sure the BO has not been marked purgeable/purged before
+        * adding the mapping.
+        * Note that we don't need to protect this test with a lock because
+        * &drm_gem_object_funcs.export() is called with
+        * &drm_device.object_lock held, and panfrost_ioctl_madvise() takes
+        * this lock before calling drm_gem_shmem_madvise() (the function that
+        * modifies bo->base.madv).
+        */
+       if (bo->base.madv == PANFROST_MADV_WILLNEED)
+               ret = -EINVAL;
+       else
+               ret = 0;
+
+       if (ret)
+               return ERR_PTR(ret);
+
+       return drm_gem_prime_export(obj, flags);
+}
+
 static int panfrost_gem_pin(struct drm_gem_object *obj)
 {
        if (to_panfrost_bo(obj)->is_heap)
@@ -112,6 +138,7 @@ static const struct drm_gem_object_funcs panfrost_gem_funcs 
= {
        .open = panfrost_gem_open,
        .close = panfrost_gem_close,
        .print_info = drm_gem_shmem_print_info,
+       .export = panfrost_gem_export,
        .pin = panfrost_gem_pin,
        .unpin = drm_gem_shmem_unpin,
        .get_sg_table = drm_gem_shmem_get_sg_table,
-- 
2.23.0

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