xref: /freebsd/sys/x86/cpufreq/hwpstate_amd.c (revision 0e6e1f14f0a7cfabec38106e41cb2f7a39363e55)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause
3  *
4  * Copyright (c) 2005 Nate Lawson
5  * Copyright (c) 2004 Colin Percival
6  * Copyright (c) 2004-2005 Bruno Durcot
7  * Copyright (c) 2004 FUKUDA Nobuhiko
8  * Copyright (c) 2009 Michael Reifenberger
9  * Copyright (c) 2009 Norikatsu Shigemura
10  * Copyright (c) 2008-2009 Gen Otsuji
11  *
12  * This code is depending on kern_cpu.c, est.c, powernow.c, p4tcc.c, smist.c
13  * in various parts. The authors of these files are Nate Lawson,
14  * Colin Percival, Bruno Durcot, and FUKUDA Nobuhiko.
15  * This code contains patches by Michael Reifenberger and Norikatsu Shigemura.
16  * Thank you.
17  *
18  * Redistribution and use in source and binary forms, with or without
19  * modification, are permitted providing that the following conditions
20  * are met:
21  * 1. Redistributions of source code must retain the above copyright
22  *    notice, this list of conditions and the following disclaimer.
23  * 2. Redistributions in binary form must reproduce the above copyright
24  *    notice, this list of conditions and the following disclaimer in the
25  *    documentation and/or other materials provided with the distribution.
26  *
27  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR``AS IS'' AND ANY EXPRESS OR
28  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
29  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
30  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
31  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
32  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
33  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
34  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
35  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
36  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
37  * POSSIBILITY OF SUCH DAMAGE.
38  */
39 
40 /*
41  * For more info:
42  * BIOS and Kernel Developer's Guide(BKDG) for AMD Family 10h Processors
43  * 31116 Rev 3.20  February 04, 2009
44  * BIOS and Kernel Developer's Guide(BKDG) for AMD Family 11h Processors
45  * 41256 Rev 3.00 - July 07, 2008
46  * Processor Programming Reference (PPR) for AMD Family 1Ah Model 02h,
47  * Revision C1 Processors Volume 1 of 7 - Sep 29, 2024
48  */
49 
50 #include <sys/param.h>
51 #include <sys/bus.h>
52 #include <sys/cpu.h>
53 #include <sys/kernel.h>
54 #include <sys/module.h>
55 #include <sys/malloc.h>
56 #include <sys/proc.h>
57 #include <sys/pcpu.h>
58 #include <sys/smp.h>
59 #include <sys/sched.h>
60 
61 #include <machine/md_var.h>
62 #include <machine/cputypes.h>
63 #include <machine/specialreg.h>
64 
65 #include <contrib/dev/acpica/include/acpi.h>
66 
67 #include <dev/acpica/acpivar.h>
68 
69 #include "acpi_if.h"
70 #include "cpufreq_if.h"
71 
72 #define	MSR_AMD_10H_11H_LIMIT	0xc0010061
73 #define	MSR_AMD_10H_11H_CONTROL	0xc0010062
74 #define	MSR_AMD_10H_11H_STATUS	0xc0010063
75 #define	MSR_AMD_10H_11H_CONFIG	0xc0010064
76 
77 #define	AMD_10H_11H_MAX_STATES	16
78 
79 /* for MSR_AMD_10H_11H_LIMIT C001_0061 */
80 #define	AMD_10H_11H_GET_PSTATE_MAX_VAL(msr)	(((msr) >> 4) & 0x7)
81 #define	AMD_10H_11H_GET_PSTATE_LIMIT(msr)	(((msr)) & 0x7)
82 /* for MSR_AMD_10H_11H_CONFIG 10h:C001_0064:68 / 11h:C001_0064:6B */
83 #define	AMD_10H_11H_CUR_VID(msr)		(((msr) >> 9) & 0x7F)
84 #define	AMD_10H_11H_CUR_DID(msr)		(((msr) >> 6) & 0x07)
85 #define	AMD_10H_11H_CUR_FID(msr)		((msr) & 0x3F)
86 
87 #define	AMD_17H_CUR_IDIV(msr)			(((msr) >> 30) & 0x03)
88 #define	AMD_17H_CUR_IDD(msr)			(((msr) >> 22) & 0xFF)
89 #define	AMD_17H_CUR_VID(msr)			(((msr) >> 14) & 0xFF)
90 #define	AMD_17H_CUR_DID(msr)			(((msr) >> 8) & 0x3F)
91 #define	AMD_17H_CUR_FID(msr)			((msr) & 0xFF)
92 
93 #define	AMD_1AH_CUR_FID(msr)			((msr) & 0xFFF)
94 
95 #define	HWPSTATE_DEBUG(dev, msg...)			\
96 	do {						\
97 		if (hwpstate_verbose)			\
98 			device_printf(dev, msg);	\
99 	} while (0)
100 
101 struct hwpstate_setting {
102 	int	freq;		/* CPU clock in Mhz or 100ths of a percent. */
103 	int	volts;		/* Voltage in mV. */
104 	int	power;		/* Power consumed in mW. */
105 	int	lat;		/* Transition latency in us. */
106 	int	pstate_id;	/* P-State id */
107 };
108 
109 struct hwpstate_softc {
110 	device_t		dev;
111 	struct hwpstate_setting	hwpstate_settings[AMD_10H_11H_MAX_STATES];
112 	int			cfnum;
113 };
114 
115 static void	hwpstate_identify(driver_t *driver, device_t parent);
116 static int	hwpstate_probe(device_t dev);
117 static int	hwpstate_attach(device_t dev);
118 static int	hwpstate_detach(device_t dev);
119 static int	hwpstate_set(device_t dev, const struct cf_setting *cf);
120 static int	hwpstate_get(device_t dev, struct cf_setting *cf);
121 static int	hwpstate_settings(device_t dev, struct cf_setting *sets, int *count);
122 static int	hwpstate_type(device_t dev, int *type);
123 static int	hwpstate_shutdown(device_t dev);
124 static int	hwpstate_features(driver_t *driver, u_int *features);
125 static int	hwpstate_get_info_from_acpi_perf(device_t dev, device_t perf_dev);
126 static int	hwpstate_get_info_from_msr(device_t dev);
127 static int	hwpstate_goto_pstate(device_t dev, int pstate_id);
128 
129 static int	hwpstate_verbose;
130 SYSCTL_INT(_debug, OID_AUTO, hwpstate_verbose, CTLFLAG_RWTUN,
131     &hwpstate_verbose, 0, "Debug hwpstate");
132 
133 static int	hwpstate_verify;
134 SYSCTL_INT(_debug, OID_AUTO, hwpstate_verify, CTLFLAG_RWTUN,
135     &hwpstate_verify, 0, "Verify P-state after setting");
136 
137 static bool	hwpstate_pstate_limit;
138 SYSCTL_BOOL(_debug, OID_AUTO, hwpstate_pstate_limit, CTLFLAG_RWTUN,
139     &hwpstate_pstate_limit, 0,
140     "If enabled (1), limit administrative control of P-states to the value in "
141     "CurPstateLimit");
142 
143 static device_method_t hwpstate_methods[] = {
144 	/* Device interface */
145 	DEVMETHOD(device_identify,	hwpstate_identify),
146 	DEVMETHOD(device_probe,		hwpstate_probe),
147 	DEVMETHOD(device_attach,	hwpstate_attach),
148 	DEVMETHOD(device_detach,	hwpstate_detach),
149 	DEVMETHOD(device_shutdown,	hwpstate_shutdown),
150 
151 	/* cpufreq interface */
152 	DEVMETHOD(cpufreq_drv_set,	hwpstate_set),
153 	DEVMETHOD(cpufreq_drv_get,	hwpstate_get),
154 	DEVMETHOD(cpufreq_drv_settings,	hwpstate_settings),
155 	DEVMETHOD(cpufreq_drv_type,	hwpstate_type),
156 
157 	/* ACPI interface */
158 	DEVMETHOD(acpi_get_features,	hwpstate_features),
159 	{0, 0}
160 };
161 
162 static driver_t hwpstate_driver = {
163 	"hwpstate",
164 	hwpstate_methods,
165 	sizeof(struct hwpstate_softc),
166 };
167 
168 DRIVER_MODULE(hwpstate, cpu, hwpstate_driver, 0, 0);
169 
170 static int
171 hwpstate_amd_iscale(int val, int div)
172 {
173 	switch (div) {
174 	case 3: /* divide by 1000 */
175 		val /= 10;
176 	case 2: /* divide by 100 */
177 		val /= 10;
178 	case 1: /* divide by 10 */
179 		val /= 10;
180 	case 0: /* divide by 1 */
181 	    ;
182 	}
183 
184 	return (val);
185 }
186 
187 /*
188  * Go to Px-state on all cpus, considering the limit register (if so
189  * configured).
190  */
191 static int
192 hwpstate_goto_pstate(device_t dev, int id)
193 {
194 	sbintime_t sbt;
195 	uint64_t msr;
196 	int cpu, i, j, limit;
197 
198 	if (hwpstate_pstate_limit) {
199 		/* get the current pstate limit */
200 		msr = rdmsr(MSR_AMD_10H_11H_LIMIT);
201 		limit = AMD_10H_11H_GET_PSTATE_LIMIT(msr);
202 		if (limit > id) {
203 			HWPSTATE_DEBUG(dev, "Restricting requested P%d to P%d "
204 			    "due to HW limit\n", id, limit);
205 			id = limit;
206 		}
207 	}
208 
209 	cpu = curcpu;
210 	HWPSTATE_DEBUG(dev, "setting P%d-state on cpu%d\n", id, cpu);
211 	/* Go To Px-state */
212 	wrmsr(MSR_AMD_10H_11H_CONTROL, id);
213 
214 	/*
215 	 * We are going to the same Px-state on all cpus.
216 	 * Probably should take _PSD into account.
217 	 */
218 	CPU_FOREACH(i) {
219 		if (i == cpu)
220 			continue;
221 
222 		/* Bind to each cpu. */
223 		thread_lock(curthread);
224 		sched_bind(curthread, i);
225 		thread_unlock(curthread);
226 		HWPSTATE_DEBUG(dev, "setting P%d-state on cpu%d\n", id, i);
227 		/* Go To Px-state */
228 		wrmsr(MSR_AMD_10H_11H_CONTROL, id);
229 	}
230 
231 	/*
232 	 * Verify whether each core is in the requested P-state.
233 	 */
234 	if (hwpstate_verify) {
235 		CPU_FOREACH(i) {
236 			thread_lock(curthread);
237 			sched_bind(curthread, i);
238 			thread_unlock(curthread);
239 			/* wait loop (100*100 usec is enough ?) */
240 			for (j = 0; j < 100; j++) {
241 				/* get the result. not assure msr=id */
242 				msr = rdmsr(MSR_AMD_10H_11H_STATUS);
243 				if (msr == id)
244 					break;
245 				sbt = SBT_1MS / 10;
246 				tsleep_sbt(dev, PZERO, "pstate_goto", sbt,
247 				    sbt >> tc_precexp, 0);
248 			}
249 			HWPSTATE_DEBUG(dev, "result: P%d-state on cpu%d\n",
250 			    (int)msr, i);
251 			if (msr != id) {
252 				HWPSTATE_DEBUG(dev,
253 				    "error: loop is not enough.\n");
254 				return (ENXIO);
255 			}
256 		}
257 	}
258 
259 	return (0);
260 }
261 
262 static int
263 hwpstate_set(device_t dev, const struct cf_setting *cf)
264 {
265 	struct hwpstate_softc *sc;
266 	struct hwpstate_setting *set;
267 	int i;
268 
269 	if (cf == NULL)
270 		return (EINVAL);
271 	sc = device_get_softc(dev);
272 	set = sc->hwpstate_settings;
273 	for (i = 0; i < sc->cfnum; i++)
274 		if (CPUFREQ_CMP(cf->freq, set[i].freq))
275 			break;
276 	if (i == sc->cfnum)
277 		return (EINVAL);
278 
279 	return (hwpstate_goto_pstate(dev, set[i].pstate_id));
280 }
281 
282 static int
283 hwpstate_get(device_t dev, struct cf_setting *cf)
284 {
285 	struct hwpstate_softc *sc;
286 	struct hwpstate_setting set;
287 	uint64_t msr;
288 
289 	sc = device_get_softc(dev);
290 	if (cf == NULL)
291 		return (EINVAL);
292 	msr = rdmsr(MSR_AMD_10H_11H_STATUS);
293 	if (msr >= sc->cfnum)
294 		return (EINVAL);
295 	set = sc->hwpstate_settings[msr];
296 
297 	cf->freq = set.freq;
298 	cf->volts = set.volts;
299 	cf->power = set.power;
300 	cf->lat = set.lat;
301 	cf->dev = dev;
302 	return (0);
303 }
304 
305 static int
306 hwpstate_settings(device_t dev, struct cf_setting *sets, int *count)
307 {
308 	struct hwpstate_softc *sc;
309 	struct hwpstate_setting set;
310 	int i;
311 
312 	if (sets == NULL || count == NULL)
313 		return (EINVAL);
314 	sc = device_get_softc(dev);
315 	if (*count < sc->cfnum)
316 		return (E2BIG);
317 	for (i = 0; i < sc->cfnum; i++, sets++) {
318 		set = sc->hwpstate_settings[i];
319 		sets->freq = set.freq;
320 		sets->volts = set.volts;
321 		sets->power = set.power;
322 		sets->lat = set.lat;
323 		sets->dev = dev;
324 	}
325 	*count = sc->cfnum;
326 
327 	return (0);
328 }
329 
330 static int
331 hwpstate_type(device_t dev, int *type)
332 {
333 
334 	if (type == NULL)
335 		return (EINVAL);
336 
337 	*type = CPUFREQ_TYPE_ABSOLUTE;
338 	return (0);
339 }
340 
341 static void
342 hwpstate_identify(driver_t *driver, device_t parent)
343 {
344 
345 	if (device_find_child(parent, "hwpstate", -1) != NULL)
346 		return;
347 
348 	if ((cpu_vendor_id != CPU_VENDOR_AMD || CPUID_TO_FAMILY(cpu_id) < 0x10) &&
349 	    cpu_vendor_id != CPU_VENDOR_HYGON)
350 		return;
351 
352 	/*
353 	 * Check if hardware pstate enable bit is set.
354 	 */
355 	if ((amd_pminfo & AMDPM_HW_PSTATE) == 0) {
356 		HWPSTATE_DEBUG(parent, "hwpstate enable bit is not set.\n");
357 		return;
358 	}
359 
360 	if (resource_disabled("hwpstate", 0))
361 		return;
362 
363 	if (BUS_ADD_CHILD(parent, 10, "hwpstate", device_get_unit(parent))
364 	    == NULL)
365 		device_printf(parent, "hwpstate: add child failed\n");
366 }
367 
368 static int
369 hwpstate_probe(device_t dev)
370 {
371 	struct hwpstate_softc *sc;
372 	device_t perf_dev;
373 	uint64_t msr;
374 	int error, type;
375 
376 	/*
377 	 * Only hwpstate0.
378 	 * It goes well with acpi_throttle.
379 	 */
380 	if (device_get_unit(dev) != 0)
381 		return (ENXIO);
382 
383 	sc = device_get_softc(dev);
384 	sc->dev = dev;
385 
386 	/*
387 	 * Check if acpi_perf has INFO only flag.
388 	 */
389 	perf_dev = device_find_child(device_get_parent(dev), "acpi_perf", -1);
390 	error = TRUE;
391 	if (perf_dev && device_is_attached(perf_dev)) {
392 		error = CPUFREQ_DRV_TYPE(perf_dev, &type);
393 		if (error == 0) {
394 			if ((type & CPUFREQ_FLAG_INFO_ONLY) == 0) {
395 				/*
396 				 * If acpi_perf doesn't have INFO_ONLY flag,
397 				 * it will take care of pstate transitions.
398 				 */
399 				HWPSTATE_DEBUG(dev, "acpi_perf will take care of pstate transitions.\n");
400 				return (ENXIO);
401 			} else {
402 				/*
403 				 * If acpi_perf has INFO_ONLY flag, (_PCT has FFixedHW)
404 				 * we can get _PSS info from acpi_perf
405 				 * without going into ACPI.
406 				 */
407 				HWPSTATE_DEBUG(dev, "going to fetch info from acpi_perf\n");
408 				error = hwpstate_get_info_from_acpi_perf(dev, perf_dev);
409 			}
410 		}
411 	}
412 
413 	if (error == 0) {
414 		/*
415 		 * Now we get _PSS info from acpi_perf without error.
416 		 * Let's check it.
417 		 */
418 		msr = rdmsr(MSR_AMD_10H_11H_LIMIT);
419 		if (sc->cfnum != 1 + AMD_10H_11H_GET_PSTATE_MAX_VAL(msr)) {
420 			HWPSTATE_DEBUG(dev, "MSR (%jd) and ACPI _PSS (%d)"
421 			    " count mismatch\n", (intmax_t)msr, sc->cfnum);
422 			error = TRUE;
423 		}
424 	}
425 
426 	/*
427 	 * If we cannot get info from acpi_perf,
428 	 * Let's get info from MSRs.
429 	 */
430 	if (error)
431 		error = hwpstate_get_info_from_msr(dev);
432 	if (error)
433 		return (error);
434 
435 	device_set_desc(dev, "Cool`n'Quiet 2.0");
436 	return (0);
437 }
438 
439 static int
440 hwpstate_attach(device_t dev)
441 {
442 
443 	return (cpufreq_register(dev));
444 }
445 
446 static int
447 hwpstate_get_info_from_msr(device_t dev)
448 {
449 	struct hwpstate_softc *sc;
450 	struct hwpstate_setting *hwpstate_set;
451 	uint64_t msr;
452 	int family, i, fid, did;
453 
454 	family = CPUID_TO_FAMILY(cpu_id);
455 	sc = device_get_softc(dev);
456 	/* Get pstate count */
457 	msr = rdmsr(MSR_AMD_10H_11H_LIMIT);
458 	sc->cfnum = 1 + AMD_10H_11H_GET_PSTATE_MAX_VAL(msr);
459 	hwpstate_set = sc->hwpstate_settings;
460 	for (i = 0; i < sc->cfnum; i++) {
461 		msr = rdmsr(MSR_AMD_10H_11H_CONFIG + i);
462 		if ((msr & ((uint64_t)1 << 63)) == 0) {
463 			HWPSTATE_DEBUG(dev, "msr is not valid.\n");
464 			return (ENXIO);
465 		}
466 		did = AMD_10H_11H_CUR_DID(msr);
467 		fid = AMD_10H_11H_CUR_FID(msr);
468 
469 		hwpstate_set[i].volts = CPUFREQ_VAL_UNKNOWN;
470 		hwpstate_set[i].power = CPUFREQ_VAL_UNKNOWN;
471 		hwpstate_set[i].lat = CPUFREQ_VAL_UNKNOWN;
472 		/* Convert fid/did to frequency. */
473 		switch (family) {
474 		case 0x11:
475 			hwpstate_set[i].freq = (100 * (fid + 0x08)) >> did;
476 			break;
477 		case 0x10:
478 		case 0x12:
479 		case 0x15:
480 		case 0x16:
481 			hwpstate_set[i].freq = (100 * (fid + 0x10)) >> did;
482 			break;
483 		case 0x17:
484 		case 0x18:
485 		case 0x19:
486 		case 0x1A:
487 			/* calculate freq */
488 			if (family == 0x1A) {
489 				fid = AMD_1AH_CUR_FID(msr);
490 				/* 1Ah CPU don't use a divisor */
491 				hwpstate_set[i].freq = fid;
492 				if (fid > 0x0f)
493 					hwpstate_set[i].freq *= 5;
494 				else {
495 					HWPSTATE_DEBUG(dev,
496 					    "unexpected fid: %d\n", fid);
497 					return (ENXIO);
498 				}
499 			} else {
500 				did = AMD_17H_CUR_DID(msr);
501 				if (did == 0) {
502 					HWPSTATE_DEBUG(dev,
503 					    "unexpected did: 0\n");
504 					did = 1;
505 				}
506 				fid = AMD_17H_CUR_FID(msr);
507 				hwpstate_set[i].freq = (200 * fid) / did;
508 			}
509 
510 			/* Vid step is 6.25mV, so scale by 100. */
511 			hwpstate_set[i].volts =
512 			    (155000 - (625 * AMD_17H_CUR_VID(msr))) / 100;
513 			/*
514 			 * Calculate current first.
515 			 * This equation is mentioned in
516 			 * "BKDG for AMD Family 15h Models 70h-7fh Processors",
517 			 * section 2.5.2.1.6.
518 			 */
519 			hwpstate_set[i].power = AMD_17H_CUR_IDD(msr) * 1000;
520 			hwpstate_set[i].power = hwpstate_amd_iscale(
521 			    hwpstate_set[i].power, AMD_17H_CUR_IDIV(msr));
522 			hwpstate_set[i].power *= hwpstate_set[i].volts;
523 			/* Milli amps * milli volts to milli watts. */
524 			hwpstate_set[i].power /= 1000;
525 			break;
526 		default:
527 			HWPSTATE_DEBUG(dev, "get_info_from_msr: %s family"
528 			    " 0x%02x CPUs are not supported yet\n",
529 			    cpu_vendor_id == CPU_VENDOR_HYGON ? "Hygon" : "AMD",
530 			    family);
531 			return (ENXIO);
532 		}
533 		hwpstate_set[i].pstate_id = i;
534 	}
535 	return (0);
536 }
537 
538 static int
539 hwpstate_get_info_from_acpi_perf(device_t dev, device_t perf_dev)
540 {
541 	struct hwpstate_softc *sc;
542 	struct cf_setting *perf_set;
543 	struct hwpstate_setting *hwpstate_set;
544 	int count, error, i;
545 
546 	perf_set = malloc(MAX_SETTINGS * sizeof(*perf_set), M_TEMP, M_NOWAIT);
547 	if (perf_set == NULL) {
548 		HWPSTATE_DEBUG(dev, "nomem\n");
549 		return (ENOMEM);
550 	}
551 	/*
552 	 * Fetch settings from acpi_perf.
553 	 * Now it is attached, and has info only flag.
554 	 */
555 	count = MAX_SETTINGS;
556 	error = CPUFREQ_DRV_SETTINGS(perf_dev, perf_set, &count);
557 	if (error) {
558 		HWPSTATE_DEBUG(dev, "error: CPUFREQ_DRV_SETTINGS.\n");
559 		goto out;
560 	}
561 	sc = device_get_softc(dev);
562 	sc->cfnum = count;
563 	hwpstate_set = sc->hwpstate_settings;
564 	for (i = 0; i < count; i++) {
565 		if (i == perf_set[i].spec[0]) {
566 			hwpstate_set[i].pstate_id = i;
567 			hwpstate_set[i].freq = perf_set[i].freq;
568 			hwpstate_set[i].volts = perf_set[i].volts;
569 			hwpstate_set[i].power = perf_set[i].power;
570 			hwpstate_set[i].lat = perf_set[i].lat;
571 		} else {
572 			HWPSTATE_DEBUG(dev, "ACPI _PSS object mismatch.\n");
573 			error = ENXIO;
574 			goto out;
575 		}
576 	}
577 out:
578 	if (perf_set)
579 		free(perf_set, M_TEMP);
580 	return (error);
581 }
582 
583 static int
584 hwpstate_detach(device_t dev)
585 {
586 
587 	hwpstate_goto_pstate(dev, 0);
588 	return (cpufreq_unregister(dev));
589 }
590 
591 static int
592 hwpstate_shutdown(device_t dev)
593 {
594 
595 	/* hwpstate_goto_pstate(dev, 0); */
596 	return (0);
597 }
598 
599 static int
600 hwpstate_features(driver_t *driver, u_int *features)
601 {
602 
603 	/* Notify the ACPI CPU that we support direct access to MSRs */
604 	*features = ACPI_CAP_PERF_MSRS;
605 	return (0);
606 }
607