xref: /netbsd-src/sys/arch/x86/x86/errata.c (revision 2dd295436a0082eb4f8d294f4aa73c223413d0f2)
1 /*	$NetBSD: errata.c,v 1.33 2023/07/28 05:02:13 mrg Exp $	*/
2 
3 /*-
4  * Copyright (c) 2007 The NetBSD Foundation, Inc.
5  * All rights reserved.
6  *
7  * This code is derived from software contributed to The NetBSD Foundation
8  * by Andrew Doran.
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions
12  * are met:
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  *
19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29  * POSSIBILITY OF SUCH DAMAGE.
30  */
31 
32 /*
33  * Detect, report on, and work around known errata with x86 CPUs.
34  *
35  * This currently only handles AMD CPUs, and is generalised because
36  * there are quite a few problems that the BIOS can patch via MSR,
37  * but it is not known if the OS can patch these yet.  The list is
38  * expected to grow over time.
39  *
40  * The data here are from: Revision Guide for AMD Athlon 64 and
41  * AMD Opteron Processors, Publication #25759, Revision: 3.69,
42  * Issue Date: September 2006
43  *
44  * https://www.amd.com/system/files/TechDocs/25759.pdf
45  *
46  * XXX This should perhaps be integrated with the identcpu code.
47  */
48 
49 #include <sys/cdefs.h>
50 __KERNEL_RCSID(0, "$NetBSD: errata.c,v 1.33 2023/07/28 05:02:13 mrg Exp $");
51 
52 #include <sys/types.h>
53 #include <sys/systm.h>
54 
55 #include <machine/cpu.h>
56 #include <machine/cpufunc.h>
57 #include <machine/specialreg.h>
58 
59 #include <x86/cpuvar.h>
60 #include <x86/cputypes.h>
61 
62 typedef struct errata {
63 	u_short		e_num;
64 	u_short		e_reported;
65 	u_int		e_data1;
66 	const uint8_t	*e_set;
67 	bool		(*e_act)(struct cpu_info *, struct errata *);
68 	uint64_t	e_data2;
69 } errata_t;
70 
71 /* These names match names from various AMD Errata/Revision Guides. */
72 typedef enum cpurev {
73 	/* K8 / Family 0Fh */
74 	BH_E4, CH_CG, CH_D0, DH_CG, DH_D0, DH_E3, DH_E6, JH_E1,
75 	JH_E6, SH_B0, SH_B3, SH_C0, SH_CG, SH_D0, SH_E4, SH_E5,
76 
77 	/* K10 / Family 10h */
78 	DR_BA, DR_B2, DR_B3, RB_C2, RB_C3, BL_C2, BL_C3, DA_C2,
79 	DA_C3, HY_D0, HY_D1, HY_D1_G34R1,  PH_E0,
80 
81 	/* Llano / Family 12h */
82 	LN_B0,
83 
84 	/* Jaguar / Family 16h */
85 	KB_A1, ML_A1,
86 
87 	/* Zen/Zen+/Zen2 / Family 17h */
88 	ZP_B1, ZP_B2, PiR_B2, Rome_B0,
89 
90 	/* XXX client Zen2 names aren't known yet. */
91 	Z2_XB, Z2_Ren, Z2_Luc, Z2_Mat, Z2_VG, Z2_Men,
92 
93 	/* Zen3/Zen4 / Family 19h */
94 	Milan_B1, Milan_B2, Genoa_B1,
95 	OINK
96 } cpurev_t;
97 
98 /*
99  * The bit-layout in the 0x80000001 CPUID result is, with bit-size
100  * as the final number here:
101  *
102  *    resv1_4 extfam_8 extmodel_4 resv2_4 fam_4 model_4 stepping_4
103  *
104  * The CPUREV(family,model,stepping) macro handles the mapping for
105  * family 6 and family 15 in the "fam_4" nybble, if 6 or 15, the
106  * extended model is present and is bit-concatenated, and if 15,
107  * the extended family is additional (ie, family 0x10 is 0xF in
108  * fam_4 and 0x01 in extfam_8.)
109  */
110 #define CPUREV(fam,mod,step)				\
111 	(((fam) > 0xf ?					\
112 	  (0xf << 8) | ((fam) - 0xf) << 20 :		\
113 	  (fam) << 8) |					\
114 	 (((mod) & 0xf) << 4) |				\
115 	 (((fam) == 6 || ((fam) >= 0xf)) ?		\
116 	  ((mod) & 0xf0) << 12 : 0) |			\
117 	 ((step) & 0xf))
118 static const u_int cpurevs[] = {
119 	BH_E4,		CPUREV(0x0F, 0x2B, 0x1),
120 	CH_CG,		CPUREV(0x0F, 0x08, 0x2),
121 	CH_CG,		CPUREV(0x0F, 0x0B, 0x2),
122 	CH_D0,		CPUREV(0x0F, 0x18, 0x0),
123 	CH_D0,		CPUREV(0x0F, 0x1B, 0x0),
124 	DH_CG,		CPUREV(0x0F, 0x0C, 0x0),
125 	DH_CG,		CPUREV(0x0F, 0x0E, 0x0),
126 	DH_CG,		CPUREV(0x0F, 0x0F, 0x0),
127 	DH_D0,		CPUREV(0x0F, 0x1C, 0x0),
128 	DH_D0,		CPUREV(0x0F, 0x1F, 0x0),
129 	DH_E3,		CPUREV(0x0F, 0x2C, 0x0),
130 	DH_E3,		CPUREV(0x0F, 0x2F, 0x0),
131 	DH_E6,		CPUREV(0x0F, 0x2C, 0x2),
132 	DH_E6,		CPUREV(0x0F, 0x2F, 0x2),
133 	JH_E1,		CPUREV(0x0F, 0x21, 0x0),
134 	JH_E6,		CPUREV(0x0F, 0x21, 0x2),
135 	JH_E6,		CPUREV(0x0F, 0x23, 0x2),
136 	SH_B0,		CPUREV(0x0F, 0x04, 0x0),
137 	SH_B3,		CPUREV(0x0F, 0x05, 0x1),
138 	SH_C0,		CPUREV(0x0F, 0x04, 0x8),
139 	SH_C0,		CPUREV(0x0F, 0x05, 0x8),
140 	SH_CG,		CPUREV(0x0F, 0x04, 0xA),
141 	SH_CG,		CPUREV(0x0F, 0x05, 0xA),
142 	SH_CG,		CPUREV(0x0F, 0x07, 0xA),
143 	SH_D0,		CPUREV(0x0F, 0x14, 0x0),
144 	SH_D0,		CPUREV(0x0F, 0x15, 0x0),
145 	SH_D0,		CPUREV(0x0F, 0x17, 0x0),
146 	SH_E4,		CPUREV(0x0F, 0x25, 0x1),
147 	SH_E4,		CPUREV(0x0F, 0x27, 0x1),
148 	SH_E5,		CPUREV(0x0F, 0x24, 0x2),
149 
150 	DR_BA,		CPUREV(0x10, 0x02, 0xA),
151 	DR_B2,		CPUREV(0x10, 0x02, 0x2),
152 	DR_B3,		CPUREV(0x10, 0x02, 0x3),
153 	RB_C2,		CPUREV(0x10, 0x04, 0x2),
154 	RB_C3,		CPUREV(0x10, 0x04, 0x3),
155 	BL_C2,		CPUREV(0x10, 0x05, 0x2),
156 	BL_C3,		CPUREV(0x10, 0x05, 0x3),
157 	DA_C2,		CPUREV(0x10, 0x06, 0x2),
158 	DA_C3,		CPUREV(0x10, 0x06, 0x3),
159 	HY_D0,		CPUREV(0x10, 0x08, 0x0),
160 	HY_D1,		CPUREV(0x10, 0x08, 0x1),
161 	HY_D1_G34R1,	CPUREV(0x10, 0x09, 0x1),
162 	PH_E0,		CPUREV(0x10, 0x0A, 0x0),
163 
164 	LN_B0,		CPUREV(0x12, 0x01, 0x0),
165 
166 	KB_A1,		CPUREV(0x16, 0x00, 0x1),
167 	ML_A1,		CPUREV(0x16, 0x30, 0x1),
168 
169 	ZP_B1,		CPUREV(0x17, 0x01, 0x1),
170 	ZP_B2,		CPUREV(0x17, 0x01, 0x2),
171 	PiR_B2,		CPUREV(0x17, 0x08, 0x2),
172 	Rome_B0,	CPUREV(0x17, 0x31, 0x0),
173 	Z2_XB,		CPUREV(0x17, 0x47, 0x0),
174 	Z2_Ren,		CPUREV(0x17, 0x60, 0x1),
175 	Z2_Luc,		CPUREV(0x17, 0x68, 0x1),
176 	Z2_Mat,		CPUREV(0x17, 0x71, 0x0),
177 	Z2_VG,		CPUREV(0x17, 0x90, 0x2),
178 	Z2_Men,		CPUREV(0x17, 0xA0, 0x0),
179 
180 	Milan_B1,	CPUREV(0x19, 0x01, 0x1),
181 	Milan_B2,	CPUREV(0x19, 0x01, 0x2),
182 	Genoa_B1,	CPUREV(0x19, 0x11, 0x1),
183 	OINK
184 };
185 
186 static const uint8_t x86_errata_set1[] = {
187 	SH_B3, SH_C0, SH_CG, DH_CG, CH_CG, OINK
188 };
189 
190 static const uint8_t x86_errata_set2[] = {
191 	SH_B3, SH_C0, SH_CG, DH_CG, CH_CG, SH_D0, DH_D0, CH_D0, OINK
192 };
193 
194 static const uint8_t x86_errata_set3[] = {
195 	JH_E1, DH_E3, OINK
196 };
197 
198 static const uint8_t x86_errata_set4[] = {
199 	SH_C0, SH_CG, DH_CG, CH_CG, SH_D0, DH_D0, CH_D0, JH_E1,
200 	DH_E3, SH_E4, BH_E4, SH_E5, DH_E6, JH_E6, OINK
201 };
202 
203 static const uint8_t x86_errata_set5[] = {
204 	SH_B3, OINK
205 };
206 
207 static const uint8_t x86_errata_set6[] = {
208 	SH_C0, SH_CG, DH_CG, CH_CG, OINK
209 };
210 
211 static const uint8_t x86_errata_set7[] = {
212 	SH_C0, SH_CG, DH_CG, CH_CG, SH_D0, DH_D0, CH_D0, OINK
213 };
214 
215 static const uint8_t x86_errata_set8[] = {
216 	BH_E4, CH_CG, CH_CG, CH_D0, CH_D0, DH_CG, DH_CG, DH_CG,
217 	DH_D0, DH_D0, DH_E3, DH_E3, DH_E6, DH_E6, JH_E1, JH_E6,
218 	JH_E6, SH_B0, SH_B3, SH_C0, SH_C0, SH_CG, SH_CG, SH_CG,
219 	SH_D0, SH_D0, SH_D0, SH_E4, SH_E4, SH_E5, OINK
220 };
221 
222 static const uint8_t x86_errata_set9[] = {
223 	DR_BA, DR_B2, OINK
224 };
225 
226 static const uint8_t x86_errata_set10[] = {
227 	DR_BA, DR_B2, DR_B3, OINK
228 };
229 
230 static const uint8_t x86_errata_set11[] = {
231 	DR_BA, DR_B2, DR_B3, RB_C2, RB_C3, BL_C2, BL_C3, DA_C2,
232 	DA_C3, HY_D0, HY_D1, HY_D1_G34R1,  PH_E0, LN_B0, OINK
233 };
234 
235 static const uint8_t x86_errata_set12[] = {
236 	KB_A1, OINK
237 };
238 
239 static const uint8_t x86_errata_set13[] = {
240 	ZP_B1, ZP_B2, PiR_B2, OINK
241 };
242 
243 static const uint8_t x86_errata_set14[] = {
244 	ZP_B1, OINK
245 };
246 
247 static const uint8_t x86_errata_set15[] = {
248 	KB_A1, ML_A1, OINK
249 };
250 
251 static const uint8_t x86_errata_set16[] = {
252 	Rome_B0, Z2_XB, Z2_Ren, Z2_Luc, Z2_Mat, Z2_VG, Z2_Men, OINK
253 };
254 
255 static bool x86_errata_setmsr(struct cpu_info *, errata_t *);
256 static bool x86_errata_testmsr(struct cpu_info *, errata_t *);
257 
258 static errata_t errata[] = {
259 	/*
260 	 * 81: Cache Coherency Problem with Hardware Prefetching
261 	 * and Streaming Stores
262 	 */
263 	{
264 		81, FALSE, MSR_DC_CFG, x86_errata_set5,
265 		x86_errata_testmsr, DC_CFG_DIS_SMC_CHK_BUF
266 	},
267 	/*
268 	 * 86: DRAM Data Masking Feature Can Cause ECC Failures
269 	 */
270 	{
271 		86, FALSE, MSR_NB_CFG, x86_errata_set1,
272 		x86_errata_testmsr, NB_CFG_DISDATMSK
273 	},
274 	/*
275 	 * 89: Potential Deadlock With Locked Transactions
276 	 */
277 	{
278 		89, FALSE, MSR_NB_CFG, x86_errata_set8,
279 		x86_errata_testmsr, NB_CFG_DISIOREQLOCK
280 	},
281 	/*
282 	 * 94: Sequential Prefetch Feature May Cause Incorrect
283 	 * Processor Operation
284 	 */
285 	{
286 		94, FALSE, MSR_IC_CFG, x86_errata_set1,
287 		x86_errata_testmsr, IC_CFG_DIS_SEQ_PREFETCH
288 	},
289 	/*
290 	 * 97: 128-Bit Streaming Stores May Cause Coherency
291 	 * Failure
292 	 *
293 	 * XXX "This workaround must not be applied to processors
294 	 * prior to revision C0."  We don't apply it, but if it
295 	 * can't be applied, it shouldn't be reported.
296 	 */
297 	{
298 		97, FALSE, MSR_DC_CFG, x86_errata_set6,
299 		x86_errata_testmsr, DC_CFG_DIS_CNV_WC_SSO
300 	},
301 	/*
302 	 * 104: DRAM Data Masking Feature Causes ChipKill ECC
303 	 * Failures When Enabled With x8/x16 DRAM Devices
304 	 */
305 	{
306 		104, FALSE, MSR_NB_CFG, x86_errata_set7,
307 		x86_errata_testmsr, NB_CFG_DISDATMSK
308 	},
309 	/*
310 	 * 113: Enhanced Write-Combining Feature Causes System Hang
311 	 */
312 	{
313 		113, FALSE, MSR_BU_CFG, x86_errata_set3,
314 		x86_errata_setmsr, BU_CFG_WBENHWSBDIS
315 	},
316 	/*
317 	 * 69: Multiprocessor Coherency Problem with Hardware
318 	 * Prefetch Mechanism
319 	 */
320 	{
321 		69, FALSE, MSR_BU_CFG, x86_errata_set5,
322 		x86_errata_setmsr, BU_CFG_WBPFSMCCHKDIS
323 	},
324 	/*
325 	 * 101: DRAM Scrubber May Cause Data Corruption When Using
326 	 * Node-Interleaved Memory
327 	 */
328 	{
329 		101, FALSE, 0, x86_errata_set2,
330 		NULL, 0
331 	},
332 	/*
333 	 * 106: Potential Deadlock with Tightly Coupled Semaphores
334 	 * in an MP System
335 	 */
336 	{
337 		106, FALSE, MSR_LS_CFG, x86_errata_set2,
338 		x86_errata_testmsr, LS_CFG_DIS_LS2_SQUISH
339 	},
340 	/*
341 	 * 107: Possible Multiprocessor Coherency Problem with
342 	 * Setting Page Table A/D Bits
343 	 */
344 	{
345 		107, FALSE, MSR_BU_CFG, x86_errata_set2,
346 		x86_errata_testmsr, BU_CFG_THRL2IDXCMPDIS
347 	},
348 	/*
349 	 * 122: TLB Flush Filter May Cause Coherency Problem in
350 	 * Multiprocessor Systems
351 	 */
352 	{
353 		122, FALSE, MSR_HWCR, x86_errata_set4,
354 		x86_errata_setmsr, HWCR_FFDIS
355 	},
356 	/*
357 	 * 254: Internal Resource Livelock Involving Cached TLB Reload
358 	 */
359 	{
360 		254, FALSE, MSR_BU_CFG, x86_errata_set9,
361 		x86_errata_testmsr, BU_CFG_ERRATA_254
362 	},
363 	/*
364 	 * 261: Processor May Stall Entering Stop-Grant Due to Pending Data
365 	 * Cache Scrub
366 	 */
367 	{
368 		261, FALSE, MSR_DC_CFG, x86_errata_set10,
369 		x86_errata_testmsr, DC_CFG_ERRATA_261
370 	},
371 	/*
372 	 * 298: L2 Eviction May Occur During Processor Operation To Set
373 	 * Accessed or Dirty Bit
374 	 */
375 	{
376 		298, FALSE, MSR_HWCR, x86_errata_set9,
377 		x86_errata_testmsr, HWCR_TLBCACHEDIS
378 	},
379 	{
380 		298, FALSE, MSR_BU_CFG, x86_errata_set9,
381 		x86_errata_testmsr, BU_CFG_ERRATA_298
382 	},
383 	/*
384 	 * 309: Processor Core May Execute Incorrect Instructions on
385 	 * Concurrent L2 and Northbridge Response
386 	 */
387 	{
388 		309, FALSE, MSR_BU_CFG, x86_errata_set9,
389 		x86_errata_testmsr, BU_CFG_ERRATA_309
390 	},
391 	/*
392 	 * 721: Processor May Incorrectly Update Stack Pointer
393 	 */
394 	{
395 		721, FALSE, MSR_DE_CFG, x86_errata_set11,
396 		x86_errata_setmsr, DE_CFG_ERRATA_721
397 	},
398 	/*
399 	 * 776: Incorrect Processor Branch Prediction for Two Consecutive
400 	 * Linear Pages
401 	 */
402 	{
403 		776, FALSE, MSR_IC_CFG, x86_errata_set12,
404 		x86_errata_setmsr, IC_CFG_ERRATA_776
405 	},
406 	/*
407 	 * 793: Specific Combination of Writes to Write Combined Memory
408 	 * Types and Locked Instructions May Cause Core Hang
409 	 */
410 	{
411 		793, FALSE, MSR_LS_CFG, x86_errata_set15,
412 		x86_errata_setmsr, LS_CFG_ERRATA_793
413 	},
414 	/*
415 	 * 1021: Load Operation May Receive Stale Data From Older Store
416 	 * Operation
417 	 */
418 	{
419 		1021, FALSE, MSR_DE_CFG, x86_errata_set13,
420 		x86_errata_setmsr, DE_CFG_ERRATA_1021
421 	},
422 	/*
423 	 * 1033: A Lock Operation May Cause the System to Hang
424 	 */
425 	{
426 		1033, FALSE, MSR_LS_CFG, x86_errata_set14,
427 		x86_errata_setmsr, LS_CFG_ERRATA_1033
428 	},
429 	/*
430 	 * 1049: FCMOV Instruction May Not Execute Correctly
431 	 */
432 	{
433 		1049, FALSE, MSR_FP_CFG, x86_errata_set13,
434 		x86_errata_setmsr, FP_CFG_ERRATA_1049
435 	},
436 #if 0	/* Should we apply this errata? The other OSes don't. */
437 	/*
438 	 * 1091: Address Boundary Crossing Load Operation May Receive
439 	 * Stale Data
440 	 */
441 	{
442 		1091, FALSE, MSR_LS_CFG2, x86_errata_set13,
443 		x86_errata_setmsr, LS_CFG2_ERRATA_1091
444 	},
445 #endif
446 	/*
447 	 * 1095: Potential Violation of Read Ordering In Lock Operation
448 	 * In SMT (Simultaneous Multithreading) Mode
449 	 */
450 	{
451 		1095, FALSE, MSR_LS_CFG, x86_errata_set13,
452 		x86_errata_setmsr, LS_CFG_ERRATA_1095
453 	},
454 	/*
455 	 * Zenbleed:
456 	 * https://www.amd.com/en/resources/product-security/bulletin/amd-sb-7008.html
457 	 * https://github.com/google/security-research/security/advisories/GHSA-v6wh-rxpg-cmm8
458 	 * https://lock.cmpxchg8b.com/zenbleed.html
459 	 */
460 	{
461 		-1, FALSE, MSR_DE_CFG, x86_errata_set16,
462 		x86_errata_setmsr, DE_CFG_ERRATA_ZENBLEED,
463 	},
464 };
465 
466 static bool
467 x86_errata_testmsr(struct cpu_info *ci, errata_t *e)
468 {
469 	uint64_t val;
470 
471 	(void)ci;
472 
473 	val = rdmsr_locked(e->e_data1);
474 	if ((val & e->e_data2) != 0)
475 		return FALSE;
476 
477 	e->e_reported = TRUE;
478 	return TRUE;
479 }
480 
481 static bool
482 x86_errata_setmsr(struct cpu_info *ci, errata_t *e)
483 {
484 	uint64_t val;
485 
486 	(void)ci;
487 
488 	val = rdmsr_locked(e->e_data1);
489 	if ((val & e->e_data2) != 0)
490 		return FALSE;
491 	wrmsr_locked(e->e_data1, val | e->e_data2);
492 	aprint_debug_dev(ci->ci_dev, "erratum %d patched\n",
493 	    e->e_num);
494 
495 	return FALSE;
496 }
497 
498 void
499 x86_errata(void)
500 {
501 	struct cpu_info *ci;
502 	uint32_t descs[4];
503 	errata_t *e, *ex;
504 	cpurev_t rev;
505 	int i, j, upgrade;
506 	static int again;
507 
508 	/* don't run if we are under a hypervisor */
509 	if (cpu_feature[1] & CPUID2_RAZ)
510 		return;
511 
512 	/* only for AMD */
513 	if (cpu_vendor != CPUVENDOR_AMD)
514 		return;
515 
516 	ci = curcpu();
517 
518 	x86_cpuid(0x80000001, descs);
519 	if (CPU_IS_PRIMARY(ci)) {
520 		aprint_verbose_dev(ci->ci_dev,
521 		    "searching errata for cpu revision 0x%08"PRIx32"\n",
522 		    descs[0]);
523 	}
524 
525 	for (i = 0;; i += 2) {
526 		if ((rev = cpurevs[i]) == OINK)
527 			return;
528 		if (cpurevs[i + 1] == descs[0])
529 			break;
530 	}
531 
532 	ex = errata + __arraycount(errata);
533 	for (upgrade = 0, e = errata; e < ex; e++) {
534 		if (e->e_reported)
535 			continue;
536 		if (e->e_set != NULL) {
537 			for (j = 0; e->e_set[j] != OINK; j++)
538 				if (e->e_set[j] == rev)
539 					break;
540 			if (e->e_set[j] == OINK)
541 				continue;
542 		}
543 
544 		aprint_debug_dev(ci->ci_dev, "testing for erratum %d\n",
545 		    e->e_num);
546 
547 		if (e->e_act == NULL)
548 			e->e_reported = TRUE;
549 		else if ((*e->e_act)(ci, e) == FALSE)
550 			continue;
551 
552 		aprint_verbose_dev(ci->ci_dev, "erratum %d present\n",
553 		    e->e_num);
554 		upgrade = 1;
555 	}
556 
557 	if (upgrade && !again) {
558 		again = 1;
559 		aprint_normal_dev(ci->ci_dev, "WARNING: errata present,"
560 		    " BIOS upgrade may be\n");
561 		aprint_normal_dev(ci->ci_dev, "WARNING: necessary to ensure"
562 		    " reliable operation\n");
563 	}
564 }
565