Re: [Intel-gfx] [PATCH 4/4] drm/i915/gem: Migrate to system at dma-buf map time

["Ruhl, Michael J" <michael.j.ruhl@intel.com>]

>-----Original Message-----
>From: dri-devel <dri-devel-bounces@lists.freedesktop.org> On Behalf Of
>Thomas Hellström
>Sent: Thursday, June 24, 2021 2:31 PM
>To: intel-gfx@lists.freedesktop.org; dri-devel@lists.freedesktop.org
>Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>; Auld, Matthew
><matthew.auld@intel.com>
>Subject: [PATCH 4/4] drm/i915/gem: Migrate to system at dma-buf map time
>
>Until we support p2p dma or as a complement to that, migrate data
>to system memory at dma-buf map time if possible.
>
>Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
>---
> drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
>b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
>index 616c3a2f1baf..a52f885bc09a 100644
>--- a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
>+++ b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
>@@ -25,7 +25,14 @@ static struct sg_table *i915_gem_map_dma_buf(struct
>dma_buf_attachment *attachme
> 	struct scatterlist *src, *dst;
> 	int ret, i;
>
>-	ret = i915_gem_object_pin_pages_unlocked(obj);
>+	ret = i915_gem_object_lock_interruptible(obj, NULL);

Hmm, I believe in most cases that the caller should be holding the
lock (object dma-resv) on this object already.

I know for the dynamic version of dma-buf, there is a check to make
sure that the lock is held when called.

I think you will run into some issues if you try to get it here as well.

Mike

>+	if (ret)
>+		return ERR_PTR(ret);
>+
>+	ret = i915_gem_object_migrate(obj, NULL, INTEL_REGION_SMEM);
>+	if (!ret)
>+		ret = i915_gem_object_pin_pages(obj);
>+	i915_gem_object_unlock(obj);
> 	if (ret)
> 		goto err;
>
>--
>2.31.1

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