From 377bc0b544cae329a385a16320e178f00f6dfcde Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Tue, 13 Oct 2015 14:22:26 +0100 Subject: drm/i915: Deny wrapping an userptr into a framebuffer MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit commit cc917ab43541db3ff66d0136042686d40a1b4c9a upstream. Pinning a userptr onto the hardware raises interesting questions about the lifetime of such a surface as the framebuffer extends that life beyond the client's address space. That is the hardware will need to keep scanning out from the backing storage even after the client wants to remap its address space. As the hardware pins the backing storage, the userptr becomes invalid and this raises a WARN when the clients tries to unmap its address space. The situation can be even more complicated when the buffer is passed between processes, between a client and display server, where the lifetime and hardware access is even more confusing. Deny it. Signed-off-by: Chris Wilson Cc: Daniel Vetter Cc: Tvrtko Ursulin Cc: Michał Winiarski Reviewed-by: Tvrtko Ursulin Signed-off-by: Jani Nikula Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/i915/i915_gem_userptr.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'drivers/gpu/drm/i915/i915_gem_userptr.c') diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c index 1719078c763a..ce175d05260b 100644 --- a/drivers/gpu/drm/i915/i915_gem_userptr.c +++ b/drivers/gpu/drm/i915/i915_gem_userptr.c @@ -776,7 +776,10 @@ static const struct drm_i915_gem_object_ops i915_gem_userptr_ops = { * Also note, that the object created here is not currently a "first class" * object, in that several ioctls are banned. These are the CPU access * ioctls: mmap(), pwrite and pread. In practice, you are expected to use - * direct access via your pointer rather than use those ioctls. + * direct access via your pointer rather than use those ioctls. Another + * restriction is that we do not allow userptr surfaces to be pinned to the + * hardware and so we reject any attempt to create a framebuffer out of a + * userptr. * * If you think this is a good interface to use to pass GPU memory between * drivers, please use dma-buf instead. In fact, wherever possible use -- cgit v1.2.3