Commit 1f135a1e authored by Matthew Brost's avatar Matthew Brost
Browse files

drm/xe/vf: Use GUC_HXG_TYPE_EVENT for GuC context register 



The only case where the GuC submission backend cannot reason 100%
correctly is when a GuC context is registered during VF post-migration
recovery. In this scenario, it's possible that the GuC context register
H2G is processed, but the immediately following schedule-enable H2G gets
lost. The schedule-enable G2H "done" response is how the GuC state machine
determines whether context registration has completed.

A double register is harmless when using `GUC_HXG_TYPE_EVENT`, as GuC
simply drops the duplicate H2G. To keep things simple, use
`GUC_HXG_TYPE_EVENT` for all context registrations on VFs.

v5:
 - Check for xe_sriov_vf_migration_supported (Tomasz)
v7:
 - Add comment about subsequent protocol failures (Tomasz)
 - Modify commit message (Michal)

Signed-off-by: default avatarMatthew Brost <matthew.brost@intel.com>
Reviewed-by: default avatarMichal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: default avatarTomasz Lis <tomasz.lis@intel.com>
Link: https://lore.kernel.org/r/20251008214532.3442967-20-matthew.brost@intel.com
parent 1faeeea0

drivers/gpu/drm/xe/xe_guc_ct.c

+27 −8
Original line number Diff line number Diff line
@@ -32,6 +32,7 @@ 
#include "xe_guc_tlb_inval.h"

#include "xe_map.h"

#include "xe_pm.h"

#include "xe_sriov_vf.h"

#include "xe_trace_guc.h"



static void receive_g2h(struct xe_guc_ct *ct);
@@ -736,6 +737,28 @@ static u16 next_ct_seqno(struct xe_guc_ct *ct, bool is_g2h_fence) 
	return seqno;

}



#define MAKE_ACTION(type, __action)				\

({								\

	FIELD_PREP(GUC_HXG_MSG_0_TYPE, type) |			\

	FIELD_PREP(GUC_HXG_EVENT_MSG_0_ACTION |			\

		   GUC_HXG_EVENT_MSG_0_DATA0, __action);	\

})



static bool vf_action_can_safely_fail(struct xe_device *xe, u32 action)

{

	/*

	 * When resuming a VF, we can't reliably track whether context

	 * registration has completed in the GuC state machine. It is harmless

	 * to resend the request, as it will fail silently if GUC_HXG_TYPE_EVENT

	 * is used. Additionally, if there is an H2G protocol issue on a VF,

	 * subsequent H2G messages sent as GUC_HXG_TYPE_FAST_REQUEST will likely

	 * fail.

	 */

	return IS_SRIOV_VF(xe) && xe_sriov_vf_migration_supported(xe) &&

		(action == XE_GUC_ACTION_REGISTER_CONTEXT_MULTI_LRC ||

		 action == XE_GUC_ACTION_REGISTER_CONTEXT);

}



#define H2G_CT_HEADERS (GUC_CTB_HDR_LEN + 1) /* one DW CTB header and one DW HxG header */



static int h2g_write(struct xe_guc_ct *ct, const u32 *action, u32 len,
@@ -807,18 +830,14 @@ static int h2g_write(struct xe_guc_ct *ct, const u32 *action, u32 len, 
		FIELD_PREP(GUC_CTB_MSG_0_NUM_DWORDS, len) |

		FIELD_PREP(GUC_CTB_MSG_0_FENCE, ct_fence_value);

	if (want_response) {

		cmd[1] =

			FIELD_PREP(GUC_HXG_MSG_0_TYPE, GUC_HXG_TYPE_REQUEST) |

			FIELD_PREP(GUC_HXG_EVENT_MSG_0_ACTION |

				   GUC_HXG_EVENT_MSG_0_DATA0, action[0]);

		cmd[1] = MAKE_ACTION(GUC_HXG_TYPE_REQUEST, action[0]);

	} else if (vf_action_can_safely_fail(xe, action[0])) {

		cmd[1] = MAKE_ACTION(GUC_HXG_TYPE_EVENT, action[0]);

	} else {

		fast_req_track(ct, ct_fence_value,

			       FIELD_GET(GUC_HXG_EVENT_MSG_0_ACTION, action[0]));



		cmd[1] =

			FIELD_PREP(GUC_HXG_MSG_0_TYPE, GUC_HXG_TYPE_FAST_REQUEST) |

			FIELD_PREP(GUC_HXG_EVENT_MSG_0_ACTION |

				   GUC_HXG_EVENT_MSG_0_DATA0, action[0]);

		cmd[1] = MAKE_ACTION(GUC_HXG_TYPE_FAST_REQUEST, action[0]);

	}



	/* H2G header in cmd[1] replaces action[0] so: */