xref: /openbmc/linux/arch/arm64/kernel/suspend.c (revision 7c892383)
1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/ftrace.h>
3 #include <linux/percpu.h>
4 #include <linux/slab.h>
5 #include <linux/uaccess.h>
6 #include <linux/pgtable.h>
7 #include <linux/cpuidle.h>
8 #include <asm/alternative.h>
9 #include <asm/cacheflush.h>
10 #include <asm/cpufeature.h>
11 #include <asm/cpuidle.h>
12 #include <asm/daifflags.h>
13 #include <asm/debug-monitors.h>
14 #include <asm/exec.h>
15 #include <asm/fpsimd.h>
16 #include <asm/mte.h>
17 #include <asm/memory.h>
18 #include <asm/mmu_context.h>
19 #include <asm/smp_plat.h>
20 #include <asm/suspend.h>
21 
22 /*
23  * This is allocated by cpu_suspend_init(), and used to store a pointer to
24  * the 'struct sleep_stack_data' the contains a particular CPUs state.
25  */
26 unsigned long *sleep_save_stash;
27 
28 /*
29  * This hook is provided so that cpu_suspend code can restore HW
30  * breakpoints as early as possible in the resume path, before reenabling
31  * debug exceptions. Code cannot be run from a CPU PM notifier since by the
32  * time the notifier runs debug exceptions might have been enabled already,
33  * with HW breakpoints registers content still in an unknown state.
34  */
35 static int (*hw_breakpoint_restore)(unsigned int);
cpu_suspend_set_dbg_restorer(int (* hw_bp_restore)(unsigned int))36 void __init cpu_suspend_set_dbg_restorer(int (*hw_bp_restore)(unsigned int))
37 {
38 	/* Prevent multiple restore hook initializations */
39 	if (WARN_ON(hw_breakpoint_restore))
40 		return;
41 	hw_breakpoint_restore = hw_bp_restore;
42 }
43 
__cpu_suspend_exit(void)44 void notrace __cpu_suspend_exit(void)
45 {
46 	unsigned int cpu = smp_processor_id();
47 
48 	mte_suspend_exit();
49 
50 	/*
51 	 * We are resuming from reset with the idmap active in TTBR0_EL1.
52 	 * We must uninstall the idmap and restore the expected MMU
53 	 * state before we can possibly return to userspace.
54 	 */
55 	cpu_uninstall_idmap();
56 
57 	/* Restore CnP bit in TTBR1_EL1 */
58 	if (system_supports_cnp())
59 		cpu_replace_ttbr1(lm_alias(swapper_pg_dir), idmap_pg_dir);
60 
61 	/*
62 	 * PSTATE was not saved over suspend/resume, re-enable any detected
63 	 * features that might not have been set correctly.
64 	 */
65 	if (cpus_have_const_cap(ARM64_HAS_DIT))
66 		set_pstate_dit(1);
67 	__uaccess_enable_hw_pan();
68 
69 	/*
70 	 * Restore HW breakpoint registers to sane values
71 	 * before debug exceptions are possibly reenabled
72 	 * by cpu_suspend()s local_daif_restore() call.
73 	 */
74 	if (hw_breakpoint_restore)
75 		hw_breakpoint_restore(cpu);
76 
77 	/*
78 	 * On resume, firmware implementing dynamic mitigation will
79 	 * have turned the mitigation on. If the user has forcefully
80 	 * disabled it, make sure their wishes are obeyed.
81 	 */
82 	spectre_v4_enable_mitigation(NULL);
83 
84 	sme_suspend_exit();
85 
86 	/* Restore additional feature-specific configuration */
87 	ptrauth_suspend_exit();
88 }
89 
90 /*
91  * cpu_suspend
92  *
93  * arg: argument to pass to the finisher function
94  * fn: finisher function pointer
95  *
96  */
cpu_suspend(unsigned long arg,int (* fn)(unsigned long))97 int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
98 {
99 	int ret = 0;
100 	unsigned long flags;
101 	struct sleep_stack_data state;
102 	struct arm_cpuidle_irq_context context;
103 
104 	/* Report any MTE async fault before going to suspend */
105 	mte_suspend_enter();
106 
107 	/*
108 	 * From this point debug exceptions are disabled to prevent
109 	 * updates to mdscr register (saved and restored along with
110 	 * general purpose registers) from kernel debuggers.
111 	 *
112 	 * Strictly speaking the trace_hardirqs_off() here is superfluous,
113 	 * hardirqs should be firmly off by now. This really ought to use
114 	 * something like raw_local_daif_save().
115 	 */
116 	flags = local_daif_save();
117 
118 	/*
119 	 * Function graph tracer state gets inconsistent when the kernel
120 	 * calls functions that never return (aka suspend finishers) hence
121 	 * disable graph tracing during their execution.
122 	 */
123 	pause_graph_tracing();
124 
125 	/*
126 	 * Switch to using DAIF.IF instead of PMR in order to reliably
127 	 * resume if we're using pseudo-NMIs.
128 	 */
129 	arm_cpuidle_save_irq_context(&context);
130 
131 	ct_cpuidle_enter();
132 
133 	if (__cpu_suspend_enter(&state)) {
134 		/* Call the suspend finisher */
135 		ret = fn(arg);
136 
137 		/*
138 		 * Never gets here, unless the suspend finisher fails.
139 		 * Successful cpu_suspend() should return from cpu_resume(),
140 		 * returning through this code path is considered an error
141 		 * If the return value is set to 0 force ret = -EOPNOTSUPP
142 		 * to make sure a proper error condition is propagated
143 		 */
144 		if (!ret)
145 			ret = -EOPNOTSUPP;
146 
147 		ct_cpuidle_exit();
148 	} else {
149 		ct_cpuidle_exit();
150 		__cpu_suspend_exit();
151 	}
152 
153 	arm_cpuidle_restore_irq_context(&context);
154 
155 	unpause_graph_tracing();
156 
157 	/*
158 	 * Restore pstate flags. OS lock and mdscr have been already
159 	 * restored, so from this point onwards, debugging is fully
160 	 * reenabled if it was enabled when core started shutdown.
161 	 */
162 	local_daif_restore(flags);
163 
164 	return ret;
165 }
166 
cpu_suspend_init(void)167 static int __init cpu_suspend_init(void)
168 {
169 	/* ctx_ptr is an array of physical addresses */
170 	sleep_save_stash = kcalloc(mpidr_hash_size(), sizeof(*sleep_save_stash),
171 				   GFP_KERNEL);
172 
173 	if (WARN_ON(!sleep_save_stash))
174 		return -ENOMEM;
175 
176 	return 0;
177 }
178 early_initcall(cpu_suspend_init);
179