Re: [PATCH v3 14/16] drm/i915/pxp: Add plane decryption support

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On 4/28/2021 1:04 PM, Ville Syrjälä wrote:
On Wed, Apr 28, 2021 at 10:32:46AM -0700, Daniele Ceraolo Spurio wrote:

On 4/28/2021 5:03 AM, Ville Syrjälä wrote:
On Wed, Apr 28, 2021 at 11:25:23AM +0000, Gupta, Anshuman wrote:
-----Original Message-----
From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Sent: Wednesday, April 28, 2021 12:25 AM
To: Gupta, Anshuman <anshuman.gupta@xxxxxxxxx>
Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx; Vivi, Rodrigo <rodrigo.vivi@xxxxxxxxx>;
Bommu, Krishnaiah <krishnaiah.bommu@xxxxxxxxx>; Huang Sean Z
<sean.z.huang@xxxxxxxxx>; Gaurav, Kumar <kumar.gaurav@xxxxxxxxx>;
Ceraolo Spurio, Daniele <daniele.ceraolospurio@xxxxxxxxx>
Subject: Re: [PATCH v3 14/16] drm/i915/pxp: Add plane decryption support
Thanks Ville for review, Below are some doubts with respect to pxp state.
On Tue, Apr 27, 2021 at 04:13:11PM +0530, Anshuman Gupta wrote:
Add support to enable/disable PLANE_SURF Decryption Request bit.
It requires only to enable plane decryption support when following
condition met.
1. PXP session is enabled.
2. Buffer object is protected.

v2:
- Used gen fb obj user_flags instead gem_object_metadata. [Krishna]

v3:
- intel_pxp_gem_object_status() API changes.

v4: use intel_pxp_is_active (Daniele)

v5: rebase and use the new protected object status checker (Daniele)

v6: used plane state for plane_decryption to handle async flip
      as suggested by Ville.

Cc: Bommu Krishnaiah <krishnaiah.bommu@xxxxxxxxx>
Cc: Huang Sean Z <sean.z.huang@xxxxxxxxx>
Cc: Gaurav Kumar <kumar.gaurav@xxxxxxxxx>
Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Signed-off-by: Anshuman Gupta <anshuman.gupta@xxxxxxxxx>
Signed-off-by: Daniele Ceraolo Spurio
<daniele.ceraolospurio@xxxxxxxxx>
---
   .../gpu/drm/i915/display/intel_atomic_plane.c |  3 ++
drivers/gpu/drm/i915/display/intel_display.c  |  5 +++
   .../drm/i915/display/intel_display_types.h    |  3 ++
   .../drm/i915/display/skl_universal_plane.c    | 32 +++++++++++++++++--
   .../drm/i915/display/skl_universal_plane.h    |  1 +
   drivers/gpu/drm/i915/i915_reg.h               |  1 +
   6 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_atomic_plane.c
b/drivers/gpu/drm/i915/display/intel_atomic_plane.c
index 7bfb26ca0bd0..7057077a2b71 100644
--- a/drivers/gpu/drm/i915/display/intel_atomic_plane.c
+++ b/drivers/gpu/drm/i915/display/intel_atomic_plane.c
@@ -394,6 +394,7 @@ int intel_plane_atomic_check(struct
intel_atomic_state *state,
   		intel_atomic_get_old_crtc_state(state, crtc);
   	struct intel_crtc_state *new_crtc_state =
   		intel_atomic_get_new_crtc_state(state, crtc);
+	const struct drm_framebuffer *fb = new_plane_state->hw.fb;

   	if (new_crtc_state && new_crtc_state->bigjoiner_slave) {
   		struct intel_plane *master_plane =
@@ -409,6 +410,8 @@ int intel_plane_atomic_check(struct
intel_atomic_state *state,
   	intel_plane_copy_uapi_to_hw_state(new_plane_state,
   					  new_master_plane_state,
   					  crtc);
+	new_plane_state->plane_decryption =
+		i915_gem_object_has_valid_protection(intel_fb_obj(fb));

   	new_plane_state->uapi.visible = false;
   	if (!new_crtc_state)
diff --git a/drivers/gpu/drm/i915/display/intel_display.c
b/drivers/gpu/drm/i915/display/intel_display.c
index a10e26380ef3..55ab2d0b92d8 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -9367,6 +9367,10 @@ static int intel_atomic_check_async(struct
intel_atomic_state *state)
   			drm_dbg_kms(&i915->drm, "Color range cannot be
changed in async flip\n");
   			return -EINVAL;
   		}
+
+		/* plane decryption is allow to change only in synchronous flips
*/
+		if (old_plane_state->plane_decryption != new_plane_state-
plane_decryption)
+			return -EINVAL;
   	}

   	return 0;
@@ -12350,6 +12354,7 @@ static void readout_plane_state(struct
drm_i915_private *dev_priv)

   		crtc = intel_get_crtc_for_pipe(dev_priv, pipe);
   		crtc_state = to_intel_crtc_state(crtc->base.state);
+		intel_plane_read_hw_decryption(plane_state);
We don't have real plane state readout anyway, so seems pointless.

   		intel_set_plane_visible(crtc_state, plane_state, visible);

diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h
b/drivers/gpu/drm/i915/display/intel_display_types.h
index e2e707c4dff5..76b3bb64a36a 100644
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -617,6 +617,9 @@ struct intel_plane_state {

   	struct intel_fb_view view;

+	/* Plane pxp decryption state */
+	bool plane_decryption;
+
It's all about the plane, so the plane_ prefix is entirely redundant.
Could just call it "decrypt" I guess.

   	/* plane control register */
   	u32 ctl;

diff --git a/drivers/gpu/drm/i915/display/skl_universal_plane.c
b/drivers/gpu/drm/i915/display/skl_universal_plane.c
index 75d3ca3dbb37..74489217e580 100644
--- a/drivers/gpu/drm/i915/display/skl_universal_plane.c
+++ b/drivers/gpu/drm/i915/display/skl_universal_plane.c
@@ -17,6 +17,7 @@
   #include "intel_sprite.h"
   #include "skl_scaler.h"
   #include "skl_universal_plane.h"
+#include "pxp/intel_pxp.h"

   static const u32 skl_plane_formats[] = {
   	DRM_FORMAT_C8,
@@ -956,7 +957,7 @@ skl_program_plane(struct intel_plane *plane,
   	u8 alpha = plane_state->hw.alpha >> 8;
   	u32 plane_color_ctl = 0, aux_dist = 0;
   	unsigned long irqflags;
-	u32 keymsk, keymax;
+	u32 keymsk, keymax, plane_surf;
   	u32 plane_ctl = plane_state->ctl;

   	plane_ctl |= skl_plane_ctl_crtc(crtc_state); @@ -1037,8 +1038,15 @@
skl_program_plane(struct intel_plane *plane,
   	 * the control register just before the surface register.
   	 */
   	intel_de_write_fw(dev_priv, PLANE_CTL(pipe, plane_id), plane_ctl);
-	intel_de_write_fw(dev_priv, PLANE_SURF(pipe, plane_id),
-			  intel_plane_ggtt_offset(plane_state) + surf_addr);
+	plane_surf = intel_plane_ggtt_offset(plane_state) + surf_addr;
+
+	if (intel_pxp_is_active(&dev_priv->gt.pxp) &&
That should all be part of the state computation. And you're missing this in the
.async_flip path totally.
Hi Ville / Rodrigo / Daniele,
Is it possible to check  intel_pxp_is_active() in plane atomic check function to compute plane decryption state?
Yes, it should be possible to call that function from anywhere.

with my best knowledge session can be invalid at any time, Let's say in plane atomic check function pxp session was enabled
but while in atomic commit pxp session can be still disabled.
I can be invalidated any time after the commit anyway. What happens in
that case?
If we flip a PXP object after the relevant key has been invalidated we
just get garbage on the screen.
Note that it is understood that this is a race we can't completely close
given that the session invalidation can hit us at any time,
It should be possible if the invalidation thingy gave us a warning
ahead of time and then waited for us to actually stop scanout.

Apart from suspend/resume scenarios, invalidations mainly occur when there is an event that the HW perceives as something that could compromise the security, so the keys are revoked immediately. There is a GuC-controlled timer that can be enabled to have a grace period for the user to remove the problem before revoking the keys (I was planning to send that as a follow-up), but AFAIU there is no way to control that from the CPU.

Daniele


the aim here
is just to make the window as small as we can and replace invalid
objects with a black frame where possible.

Daniele


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