From cc917ab43541db3ff66d0136042686d40a1b4c9a Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Tue, 13 Oct 2015 14:22:26 +0100 Subject: [PATCH] drm/i915: Deny wrapping an userptr into a framebuffer MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Cc: stable@vger.kernel.org Reviewed-by: Tvrtko Ursulin Signed-off-by: Jani Nikula --- drivers/gpu/drm/i915/i915_gem_userptr.c | 5 ++++- drivers/gpu/drm/i915/intel_display.c | 5 +++++ 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c index 8fd431bcdfd3..a96b9006a51e 100644 --- a/drivers/gpu/drm/i915/i915_gem_userptr.c +++ b/drivers/gpu/drm/i915/i915_gem_userptr.c @@ -804,7 +804,10 @@ 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 diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c index 96e6c41783df..2bf248b04542 100644 --- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -14116,6 +14116,11 @@ static int intel_user_framebuffer_create_handle(struct drm_framebuffer *fb, struct intel_framebuffer *intel_fb = to_intel_framebuffer(fb); struct drm_i915_gem_object *obj = intel_fb->obj; + if (obj->userptr.mm) { + DRM_DEBUG("attempting to use a userptr for a framebuffer, denied\n"); + return -EINVAL; + } + return drm_gem_handle_create(file, &obj->base, handle); }