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2024-10-12 a5969cabbb4660eab42b6ef0412cbbd1200cf14d 
 kernel/arch/powerpc/platforms/pseries/smp.c
....@@ -1,3 +1,4 @@
1
+// SPDX-License-Identifier: GPL-2.0-or-later
12 /*
23  * SMP support for pSeries machines.
34  *
....@@ -5,11 +6,6 @@
56  * Mike Corrigan {engebret|bergner|mikec}@us.ibm.com
67  *
78  * Plus various changes from other IBM teams...
8
- *
9
- *      This program is free software; you can redistribute it and/or
10
- *      modify it under the terms of the GNU General Public License
11
- *      as published by the Free Software Foundation; either version
12
- *      2 of the License, or (at your option) any later version.
139  */
1410 
1511 
....@@ -24,12 +20,12 @@
2420 #include <linux/err.h>
2521 #include <linux/device.h>
2622 #include <linux/cpu.h>
23
+#include <linux/pgtable.h>
2724 
2825 #include <asm/ptrace.h>
2926 #include <linux/atomic.h>
3027 #include <asm/irq.h>
3128 #include <asm/page.h>
32
-#include <asm/pgtable.h>
3329 #include <asm/io.h>
3430 #include <asm/prom.h>
3531 #include <asm/smp.h>
....@@ -45,10 +41,10 @@
4541 #include <asm/dbell.h>
4642 #include <asm/plpar_wrappers.h>
4743 #include <asm/code-patching.h>
44
+#include <asm/svm.h>
45
+#include <asm/kvm_guest.h>
4846 
4947 #include "pseries.h"
50
-#include "offline_states.h"
51
-
5248 
5349 /*
5450  * The Primary thread of each non-boot processor was started from the OF client
....@@ -109,12 +105,6 @@
109105 		return 1;
110106 	}
111107 
112
-	/* Fixup atomic count: it exited inside IRQ handler. */
113
-	task_thread_info(paca_ptrs[lcpu]->__current)->preempt_count	= 0;
114
-#ifdef CONFIG_HOTPLUG_CPU
115
-	if (get_cpu_current_state(lcpu) == CPU_STATE_INACTIVE)
116
-		goto out;
117
-#endif
118108 	/* 
119109 	 * If the RTAS start-cpu token does not exist then presume the
120110 	 * cpu is already spinning.
....@@ -129,9 +119,6 @@
129119 		return 0;
130120 	}
131121 
132
-#ifdef CONFIG_HOTPLUG_CPU
133
-out:
134
-#endif
135122 	return 1;
136123 }
137124 
....@@ -146,10 +133,6 @@
146133 		vpa_init(cpu);
147134 
148135 	cpumask_clear_cpu(cpu, of_spin_mask);
149
-#ifdef CONFIG_HOTPLUG_CPU
150
-	set_cpu_current_state(cpu, CPU_STATE_ONLINE);
151
-	set_default_offline_state(cpu);
152
-#endif
153136 }
154137 
155138 static int smp_pSeries_kick_cpu(int nr)
....@@ -166,20 +149,6 @@
166149 	 * the processor will continue on to secondary_start
167150 	 */
168151 	paca_ptrs[nr]->cpu_start = 1;
169
-#ifdef CONFIG_HOTPLUG_CPU
170
-	set_preferred_offline_state(nr, CPU_STATE_ONLINE);
171
-
172
-	if (get_cpu_current_state(nr) == CPU_STATE_INACTIVE) {
173
-		long rc;
174
-		unsigned long hcpuid;
175
-
176
-		hcpuid = get_hard_smp_processor_id(nr);
177
-		rc = plpar_hcall_norets(H_PROD, hcpuid);
178
-		if (rc != H_SUCCESS)
179
-			printk(KERN_ERR "Error: Prod to wake up processor %d "
180
-						"Ret= %ld\n", nr, rc);
181
-	}
182
-#endif
183152 
184153 	return 0;
185154 }
....@@ -191,13 +160,16 @@
191160 	return 0;
192161 }
193162 
194
-static void smp_pseries_cause_ipi(int cpu)
163
+/* Cause IPI as setup by the interrupt controller (xics or xive) */
164
+static void (*ic_cause_ipi)(int cpu) __ro_after_init;
165
+
166
+/* Use msgsndp doorbells target is a sibling, else use interrupt controller */
167
+static void dbell_or_ic_cause_ipi(int cpu)
195168 {
196
-	/* POWER9 should not use this handler */
197169 	if (doorbell_try_core_ipi(cpu))
198170 		return;
199171 
200
-	icp_ops->cause_ipi(cpu);
172
+	ic_cause_ipi(cpu);
201173 }
202174 
203175 static int pseries_cause_nmi_ipi(int cpu)
....@@ -221,26 +193,51 @@
221193 	return 0;
222194 }
223195 
224
-static __init void pSeries_smp_probe_xics(void)
225
-{
226
-	xics_smp_probe();
227
-
228
-	if (cpu_has_feature(CPU_FTR_DBELL))
229
-		smp_ops->cause_ipi = smp_pseries_cause_ipi;
230
-	else
231
-		smp_ops->cause_ipi = icp_ops->cause_ipi;
232
-}
233
-
234196 static __init void pSeries_smp_probe(void)
235197 {
236198 	if (xive_enabled())
237
-		/*
238
-		 * Don't use P9 doorbells when XIVE is enabled. IPIs
239
-		 * using MMIOs should be faster
240
-		 */
241199 		xive_smp_probe();
242200 	else
243
-		pSeries_smp_probe_xics();
201
+		xics_smp_probe();
202
+
203
+	/* No doorbell facility, must use the interrupt controller for IPIs */
204
+	if (!cpu_has_feature(CPU_FTR_DBELL))
205
+		return;
206
+
207
+	/* Doorbells can only be used for IPIs between SMT siblings */
208
+	if (!cpu_has_feature(CPU_FTR_SMT))
209
+		return;
210
+
211
+	check_kvm_guest();
212
+
213
+	if (is_kvm_guest()) {
214
+		/*
215
+		 * KVM emulates doorbells by disabling FSCR[MSGP] so msgsndp
216
+		 * faults to the hypervisor which then reads the instruction
217
+		 * from guest memory, which tends to be slower than using XIVE.
218
+		 */
219
+		if (xive_enabled())
220
+			return;
221
+
222
+		/*
223
+		 * XICS hcalls aren't as fast, so we can use msgsndp (which
224
+		 * also helps exercise KVM emulation), however KVM can't
225
+		 * emulate secure guests because it can't read the instruction
226
+		 * out of their memory.
227
+		 */
228
+		if (is_secure_guest())
229
+			return;
230
+	}
231
+
232
+	/*
233
+	 * Under PowerVM, FSCR[MSGP] is enabled as guest vCPU siblings are
234
+	 * gang scheduled on the same physical core, so doorbells are always
235
+	 * faster than the interrupt controller, and they can be used by
236
+	 * secure guests.
237
+	 */
238
+
239
+	ic_cause_ipi = smp_ops->cause_ipi;
240
+	smp_ops->cause_ipi = dbell_or_ic_cause_ipi;
244241 }
245242 
246243 static struct smp_ops_t pseries_smp_ops = {