RE: [PATCH v2] drm/xe/hdcp: Add NULL check for media_gt in intel_hdcp_gsc_check_status()

[Gustavo Sousa <gustavo.sousa@intel.com>]

"Lin, Shuicheng" <shuicheng.lin@intel.com> writes:

> On Thu, Apr 16, 2026 12:38 PM Matthew Roper wrote:
>> On Thu, Apr 16, 2026 at 03:17:19PM -0300, Gustavo Sousa wrote:
>> > When media GT is disabled via configfs, there is no allocation for
>> > media_gt, which is kept as NULL.  In such scenario,
>> > intel_hdcp_gsc_check_status() results in a kernel pagefault error due
>> > to &gt->uc.gsc being evaluated as an invalid memory address.
>> >
>> > Fix that by introducing a NULL check on media_gt and bailing out early
>> > if so.
>> >
>> > While at it, also drop the NULL check for gsc, since it can't be NULL
>> > if media_gt is not NULL.
>> >
>> > v2:
>> >   - Get address for gsc only after checking that gt is not NULL.
>> >     (Shuicheng)
>> >   - Drop the NULL check for gsc. (Shuicheng)
>> >
>> > Cc: Shuicheng Lin <shuicheng.lin@intel.com>
>> > Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
>> 
>> We should probably also have
>> 
>> Fixes: 4af50beb4e0f ("drm/xe: Use gsc_proxy_init_done to check proxy
>> status")
>> Cc: <stable@vger.kernel.org> # v6.10+
>> 
>> too?  Or I guess we could make the argument that there don't seem to be any
>> real devices without the media GT, so it only became possible to trigger this
>> once we added configfs support for manually disabling GTs?
>> In that case,
>> 
>> Fixes: 7abd69278bb5 ("drm/xe/configfs: Add attribute to disable GT types")
>> Cc: <stable@vger.kernel.org> # v6.19+
>> 
>> minimizes the number of kernel versions this would be backported to.
>
> Is it possible that we have future platform that does not have media gt, and be supported with old kernel?
> For that case, it should be supported with dkms, so this Fixes tag should not affect. Is it right?
> So, I prefer this Fixes tag.
>
> LGTM.
> Reviewed-by: Shuicheng Lin <shuicheng.lin@intel.com>

Yeah, I guess it is safer to use the first proposed Fixes tag.  I'll use
that one when applying.

--
Gustavo Sousa

>
>> 
>> 
>> Anyway, the change itself is
>> 
>> Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
>> 
>> > ---
>> > Changes in v2:
>> > - EDITME: describe what is new in this series revision.
>> > - EDITME: use bulletpoints and terse descriptions.
>> > - Link to v1:
>> > https://patch.msgid.link/20260302-check-for-null-media_gt-in-intel_hdc
>> > p_gsc_check_status-v1-1-163d5f826b30@intel.com
>> > ---
>> >  drivers/gpu/drm/xe/display/xe_hdcp_gsc.c | 12 ++++++++++--
>> >  1 file changed, 10 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/drivers/gpu/drm/xe/display/xe_hdcp_gsc.c
>> > b/drivers/gpu/drm/xe/display/xe_hdcp_gsc.c
>> > index 29c72aa4b0d2..33494b86205d 100644
>> > --- a/drivers/gpu/drm/xe/display/xe_hdcp_gsc.c
>> > +++ b/drivers/gpu/drm/xe/display/xe_hdcp_gsc.c
>> > @@ -37,9 +37,17 @@ static bool intel_hdcp_gsc_check_status(struct
>> drm_device *drm)
>> >  	struct xe_device *xe = to_xe_device(drm);
>> >  	struct xe_tile *tile = xe_device_get_root_tile(xe);
>> >  	struct xe_gt *gt = tile->media_gt;
>> > -	struct xe_gsc *gsc = &gt->uc.gsc;
>> > +	struct xe_gsc *gsc;
>> > +
>> > +	if (!gt) {
>> > +		drm_dbg_kms(&xe->drm,
>> > +			    "not checking GSC status for HDCP2.x: media GT not
>> present or disabled\n");
>> > +		return false;
>> > +	}
>> > +
>> > +	gsc = &gt->uc.gsc;
>> >
>> > -	if (!gsc || !xe_uc_fw_is_available(&gsc->fw)) {
>> > +	if (!xe_uc_fw_is_available(&gsc->fw)) {
>> >  		drm_dbg_kms(&xe->drm,
>> >  			    "GSC Components not ready for HDCP2.x\n");
>> >  		return false;
>> >
>> > ---
>> > base-commit: 9ac7dca8d82a4e6d9806ac6c991f0777338833bb
>> > change-id:
>> > 20260302-check-for-null-media_gt-in-intel_hdcp_gsc_check_status-
>> 071898
>> > b8a402
>> >
>> > Best regards,
>> > --
>> > Gustavo Sousa <gustavo.sousa@intel.com>
>> >
>> 
>> --
>> Matt Roper
>> Graphics Software Engineer
>> Linux GPU Platform Enablement
>> Intel Corporation