vgsp: m86 - sticky gsp_phys_rmcall_gr_override_hex module parameter

The override blob can now be supplied at load (hex string, <= 1 page) and is
parsed at the first forwarded launch, so the minimal-kernel experiment no
longer depends on a debugfs write racing the guest's launch. Also observed in
the m86 attempt: after many failed launches the forwarded ring desynced
(USERD GP_PUT rewound to 1 while the engine's GP_GET was 513; IQ2M sentinel
intact, no FE fetch) - a fresh boot is required per experiment.

1 files changed, 17 insertions, 0 deletions

diff --git a/kernel/gsp_phys_gpu.c b/kernel/gsp_phys_gpu.c
index e3ca2e8..ee6625c 100644
--- a/kernel/gsp_phys_gpu.c
+++ b/kernel/gsp_phys_gpu.c
@@ -796,6 +796,23 @@ unsigned int gsp_phys_rmcall_gr_lmem_tpc_size_value(void)
 EXPORT_SYMBOL_GPL(gsp_phys_rmcall_gr_lmem_tpc_size_value);
 
 /*
+ * m86 sticky override (gsp_phys_rmcall_gr_override_hex; default empty): hex
+ * bytes stored into the program-page override at first forwarded launch, so
+ * the override survives every module reload without a debugfs write.
+ */
+static char *gsp_phys_rmcall_gr_override_hex_param;
+module_param_named(gsp_phys_rmcall_gr_override_hex,
+		   gsp_phys_rmcall_gr_override_hex_param, charp, 0644);
+MODULE_PARM_DESC(gsp_phys_rmcall_gr_override_hex,
+		 "Hex bytes applied to the forwarded launch's program page at the QMD offset (default empty)");
+
+const char *gsp_phys_rmcall_gr_override_hex_value(void)
+{
+	return gsp_phys_rmcall_gr_override_hex_param;
+}
+EXPORT_SYMBOL_GPL(gsp_phys_rmcall_gr_override_hex_value);
+
+/*
  * m84 ctx-image probe (gsp_phys_rmcall_gr_img_probe; default 0). After the
  * stage-4 GR sem proof the ladder re-binds the rmcall channel to COPY0,
  * copies the first 4 KB of the MAIN context image and of the VEID0 subctx