drm/xe/reg_sr: Do sanity check for MCR vs non-MCR

The type struct xe_reg_mcr exists to ensure that the correct API is used
when handling MCR registers.  However, for the register save/restore
functionality, the RTP processing always cast the register to a struct
xe_reg and then apply_one_mmio() selects the MMIO API based on the "mcr"
field of the register instance.

This allows the developer to commit mistakes like passing a MCR register
for an RTP action for a GT where the respective register is not MCR; and
vice-versa.

To capture such scenarios, do a sanity check in xe_reg_sr_add() that,
upon an inconsistency:

- "fixes" the register type by favoring what we have in our MCR range
  tables instead of what the developer selected for the save/restore
  entry;
- raises a notice-level message to inform about the inconsistency.

Note: As a collateral of this change, we need to include MCR
initialization in xe_wa_test.c, otherwise a bunch of test cases end up
failing because xe_gt_mcr_check_reg() will always return false, meaning
that will incorrectly say that a MCR register is not MCR.

v2:
  - Downgrade messages to notice level so as not to block CI execution
    when inconsistencies are found. (Matt)
  - Add missing EXPORT_SYMBOL_IF_KUNIT() calls. (Gustavo)

Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patch.msgid.link/20260514-rtp-mcr-check-v3-7-30dd47855fee@intel.com
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>

drivers/gpu/drm/xe/tests/xe_rtp_test.c

@@ -9,24 +9,30 @@
 #include <drm/drm_drv.h>
 #include <drm/drm_kunit_helpers.h>
 
+#include <kunit/static_stub.h>
 #include <kunit/test.h>
 
 #include "regs/xe_gt_regs.h"
 #include "regs/xe_reg_defs.h"
 #include "xe_device.h"
 #include "xe_device_types.h"
+#include "xe_gt_mcr.h"
 #include "xe_kunit_helpers.h"
 #include "xe_pci_test.h"
 #include "xe_reg_sr.h"
 #include "xe_rtp.h"
 
-#define REGULAR_REG1	XE_REG(1)
-#define REGULAR_REG2	XE_REG(2)
-#define REGULAR_REG3	XE_REG(3)
-#define MCR_REG1	XE_REG_MCR(1)
-#define MCR_REG2	XE_REG_MCR(2)
-#define MCR_REG3	XE_REG_MCR(3)
-#define MASKED_REG1	XE_REG(1, XE_REG_OPTION_MASKED)
+#define REGULAR_REG1		XE_REG(1)
+#define REGULAR_REG2		XE_REG(2)
+#define REGULAR_REG3		XE_REG(3)
+#define REGULAR_REG4		XE_REG(4)
+#define BAD_REGULAR_REG5	XE_REG(5)
+#define MCR_REG1		XE_REG_MCR(1)
+#define MCR_REG2		XE_REG_MCR(2)
+#define MCR_REG3		XE_REG_MCR(3)
+#define BAD_MCR_REG4		XE_REG_MCR(4)
+#define MCR_REG5		XE_REG_MCR(5)
+#define MASKED_REG1		XE_REG(1, XE_REG_OPTION_MASKED)
 
 #undef XE_REG_MCR
 #define XE_REG_MCR(...)     XE_REG(__VA_ARGS__, .mcr = 1)
@@ -48,6 +54,23 @@ struct rtp_test_case {
 	const struct xe_rtp_entry *entries;
 };
 
+static bool fake_xe_gt_mcr_check_reg(struct xe_gt *gt, struct xe_reg reg)
+{
+	/*
+	 * All supported platforms in this imaginary setup will always have REG4
+	 * as a non-MCR register and REG5 as MCR, meaning that BAD_MCR_REG4 and
+	 * BAD_REGULAR_REG5 represent programming errors to be captured by our
+	 * tests.
+	 */
+	if (reg.raw == BAD_REGULAR_REG5.raw)
+		return true;
+
+	if (reg.raw == BAD_MCR_REG4.raw)
+		return false;
+
+	return reg.mcr;
+}
+
 static bool match_yes(const struct xe_device *xe, const struct xe_gt *gt,
 		      const struct xe_hw_engine *hwe)
 {
@@ -304,6 +327,38 @@ static const struct rtp_to_sr_test_case rtp_to_sr_cases[] = {
 			{}
 		},
 	},
+	{
+		.name = "bad-mcr-reg-forced-to-regular",
+		.expected_reg = REGULAR_REG4,
+		.expected_set_bits = REG_BIT(0),
+		.expected_clr_bits = REG_BIT(0),
+		.expected_active = BIT(0),
+		.expected_count_sr_entries = 1,
+		.expected_sr_errors = 1,
+		.entries = (const struct xe_rtp_entry_sr[]) {
+			{ XE_RTP_NAME("bad-mcr-regular-reg"),
+			  XE_RTP_RULES(FUNC(match_yes)),
+			  XE_RTP_ACTIONS(SET(BAD_MCR_REG4, REG_BIT(0)))
+			},
+			{}
+		},
+	},
+	{
+		.name = "bad-regular-reg-forced-to-mcr",
+		.expected_reg = MCR_REG5,
+		.expected_set_bits = REG_BIT(0),
+		.expected_clr_bits = REG_BIT(0),
+		.expected_active = BIT(0),
+		.expected_count_sr_entries = 1,
+		.expected_sr_errors = 1,
+		.entries = (const struct xe_rtp_entry_sr[]) {
+			{ XE_RTP_NAME("bad-regular-reg"),
+			  XE_RTP_RULES(FUNC(match_yes)),
+			  XE_RTP_ACTIONS(SET(BAD_REGULAR_REG5, REG_BIT(0)))
+			},
+			{}
+		},
+	},
 };
 
 static void xe_rtp_process_to_sr_tests(struct kunit *test)
@@ -523,6 +578,8 @@ static int xe_rtp_test_init(struct kunit *test)
 	xe->drm.dev = dev;
 	test->priv = xe;
 
+	kunit_activate_static_stub(test, xe_gt_mcr_check_reg, fake_xe_gt_mcr_check_reg);
+
 	return 0;
 }
 

drivers/gpu/drm/xe/tests/xe_wa_test.c

@@ -9,6 +9,8 @@
 #include <kunit/test.h>
 
 #include "xe_device.h"
+#include "xe_gt.h"
+#include "xe_gt_mcr.h"
 #include "xe_kunit_helpers.h"
 #include "xe_pci_test.h"
 #include "xe_reg_sr.h"
@@ -19,8 +21,10 @@ static int xe_wa_test_init(struct kunit *test)
 {
 	const struct xe_pci_fake_data *param = test->param_value;
 	struct xe_pci_fake_data data = *param;
-	struct xe_device *xe;
 	struct device *dev;
+	struct xe_device *xe;
+	struct xe_gt *gt;
+	int id;
 	int ret;
 
 	dev = drm_kunit_helper_alloc_device(test);
@@ -33,6 +37,12 @@ static int xe_wa_test_init(struct kunit *test)
 	ret = xe_pci_fake_device_init(xe);
 	KUNIT_ASSERT_EQ(test, ret, 0);
 
+	/* Needed for sanitize_mcr(). */
+	for_each_gt(gt, xe, id) {
+		xe_gt_mcr_init_early(gt);
+		xe_gt_mmio_init(gt);
+	}
+
 	if (!param->graphics_verx100)
 		xe->info.step = param->step;
 

drivers/gpu/drm/xe/xe_gt.c

@@ -7,6 +7,8 @@
 
 #include <linux/minmax.h>
 
+#include <kunit/visibility.h>
+
 #include <drm/drm_managed.h>
 #include <uapi/drm/xe_drm.h>
 
@@ -785,6 +787,7 @@ void xe_gt_mmio_init(struct xe_gt *gt)
 	if (IS_SRIOV_VF(xe))
 		gt->mmio.sriov_vf_gt = gt;
 }
+EXPORT_SYMBOL_IF_KUNIT(xe_gt_mmio_init);
 
 void xe_gt_record_user_engines(struct xe_gt *gt)
 {

drivers/gpu/drm/xe/xe_gt_mcr.c

@@ -3,6 +3,9 @@
  * Copyright © 2022 Intel Corporation
  */
 
+#include <kunit/static_stub.h>
+#include <kunit/visibility.h>
+
 #include "xe_gt_mcr.h"
 
 #include "regs/xe_gt_regs.h"
@@ -553,6 +556,7 @@ void xe_gt_mcr_init_early(struct xe_gt *gt)
 	/* Mark instance 0 as initialized, we need this early for VRAM and CCS probe. */
 	gt->steering[INSTANCE0].initialized = true;
 }
+EXPORT_SYMBOL_IF_KUNIT(xe_gt_mcr_init_early);
 
 /**
  * xe_gt_mcr_init - Normal initialization of the MCR support
@@ -614,6 +618,26 @@ static bool reg_in_steering_type_ranges(struct xe_gt *gt,
 	return false;
 }
 
+/*
+ * xe_gt_mcr_check_reg - check if a register is recognized by this GT as MCR
+ * @gt: GT structure
+ * @reg: The register to check
+ *
+ * Returns true if the register offset falls within one of the MMIO ranges
+ * classified as MCR for the GT.
+ */
+bool xe_gt_mcr_check_reg(struct xe_gt *gt, struct xe_reg reg)
+{
+	KUNIT_STATIC_STUB_REDIRECT(xe_gt_mcr_check_reg, gt, reg);
+
+	for (int type = 0; type <= IMPLICIT_STEERING; type++)
+		if (reg_in_steering_type_ranges(gt, reg, type))
+			return true;
+
+	return false;
+}
+EXPORT_SYMBOL_IF_KUNIT(xe_gt_mcr_check_reg);
+
 /*
  * xe_gt_mcr_get_nonterminated_steering - find group/instance values that
  *    will steer a register to a non-terminated instance

drivers/gpu/drm/xe/xe_gt_mcr.h

@@ -26,6 +26,7 @@ void xe_gt_mcr_unicast_write(struct xe_gt *gt, struct xe_reg_mcr mcr_reg,
 void xe_gt_mcr_multicast_write(struct xe_gt *gt, struct xe_reg_mcr mcr_reg,
 			       u32 value);
 
+bool xe_gt_mcr_check_reg(struct xe_gt *gt, struct xe_reg reg);
 bool xe_gt_mcr_get_nonterminated_steering(struct xe_gt *gt,
 					  struct xe_reg_mcr reg_mcr,
 					  u8 *group, u8 *instance);

drivers/gpu/drm/xe/xe_reg_sr.c

@@ -70,14 +70,49 @@ static void reg_sr_inc_error(struct xe_reg_sr *sr)
 #endif
 }
 
+static struct xe_reg sanitize_mcr(struct xe_reg_sr *sr,
+				  const struct xe_reg_sr_entry *e,
+				  struct xe_gt *gt)
+{
+	struct xe_reg reg = e->reg;
+	bool is_mcr;
+
+	/*
+	 * We need the gt structure to check MCR ranges.
+	 */
+	if (!gt)
+		return reg;
+
+	is_mcr = xe_gt_mcr_check_reg(gt, reg);
+
+	if (is_mcr && !reg.mcr) {
+		reg.mcr = 1;
+		xe_gt_notice(gt, "xe_reg_sr_entry using non-MCR register for address 0x%x, forcing MCR\n",
+			     reg.addr);
+		reg_sr_inc_error(sr);
+	}
+
+	if (!is_mcr && reg.mcr) {
+		reg.mcr = 0;
+		xe_gt_notice(gt, "xe_reg_sr_entry using MCR register for address 0x%x, forcing non-MCR\n",
+			     reg.addr);
+		reg_sr_inc_error(sr);
+	}
+
+	return reg;
+}
+
 int xe_reg_sr_add(struct xe_reg_sr *sr,
 		  const struct xe_reg_sr_entry *e,
 		  struct xe_gt *gt)
 {
 	unsigned long idx = e->reg.addr;
 	struct xe_reg_sr_entry *pentry = xa_load(&sr->xa, idx);
+	struct xe_reg reg;
 	int ret;
 
+	reg = sanitize_mcr(sr, e, gt);
+
 	if (pentry) {
 		if (!compatible_entries(pentry, e)) {
 			ret = -EINVAL;
@@ -98,6 +133,7 @@ int xe_reg_sr_add(struct xe_reg_sr *sr,
 	}
 
 	*pentry = *e;
+	pentry->reg = reg;
 	ret = xa_err(xa_store(&sr->xa, idx, pentry, GFP_KERNEL));
 	if (ret)
 		goto fail_free;