powerpc/xive: Add a debugfs toggle for save-restore

On POWER10, the automatic "save & restore" of interrupt context is
always available. Provide a way to deactivate it for tests or
performance.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211105102636.1016378-11-clg@kaod.org

arch/powerpc/sysdev/xive/common.c

@@ -1847,6 +1847,7 @@ static void xive_core_debugfs_create(void)
 				    &xive_eq_debug_fops);
 	}
 	debugfs_create_bool("store-eoi", 0600, xive_dir, &xive_store_eoi);
+	debugfs_create_bool("save-restore", 0600, xive_dir, &xive_has_save_restore);
 }
 #else
 static inline void xive_core_debugfs_create(void) { }

arch/powerpc/sysdev/xive/native.c

@@ -41,7 +41,7 @@ static u32 xive_queue_shift;
 static u32 xive_pool_vps = XIVE_INVALID_VP;
 static struct kmem_cache *xive_provision_cache;
 static bool xive_has_single_esc;
-static bool xive_has_save_restore;
+bool xive_has_save_restore;
 
 int xive_native_populate_irq_data(u32 hw_irq, struct xive_irq_data *data)
 {

arch/powerpc/sysdev/xive/xive-internal.h

@@ -72,5 +72,6 @@ static inline u32 xive_alloc_order(u32 queue_shift)
 }
 
 extern bool xive_cmdline_disabled;
+extern bool xive_has_save_restore;
 
 #endif /*  __XIVE_INTERNAL_H */