Re: [PATCH v4] hwrng: add Zhaoxin rng driver base on rep_xstore instruction

kernel test robot
2023-12-26T00:54:29Z

Hi LeoLiu-oc,

kernel test robot noticed the following build warnings:

[auto build test WARNING on char-misc/char-misc-testing]
[also build test WARNING on char-misc/char-misc-next char-misc/char-misc-linus herbert-cryptodev-2.6/master linus/master v6.7-rc7 next-20231222]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url: https://github.com/intel-lab-lkp/linux/commits/LeoLiu-oc/hwrng-add-Zhaoxin-rng-driver-base-on-rep_xstore-instruction/20231225-153520
base: char-misc/char-misc-testing
patch link: https://lore.kernel.org/r/20231225025330.809554-1-LeoLiu-oc%40zhaoxin.com
patch subject: [PATCH v4] hwrng: add Zhaoxin rng driver base on rep_xstore instruction
config: x86_64-kexec (https://download.01.org/0day-ci/archive/20231226/202312260833.4ds3Mvav-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231226/202312260833.4ds3Mvav-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202312260833.4ds3Mvav-lkp@intel.com/

All warnings (new ones prefixed by >>):

drivers/char/hw_random/via-rng.c:220:26: error: conflicting types for 'via_rng_cpu_id'; have 'struct x86_cpu_id[]'
220 | static struct x86_cpu_id via_rng_cpu_id[] = {
| ^~~~~~~~~~~~~~
drivers/char/hw_random/via-rng.c:38:32: note: previous declaration of 'via_rng_cpu_id' with type 'const struct x86_cpu_id[]'
38 | static const struct x86_cpu_id via_rng_cpu_id[];
| ^~~~~~~~~~~~~~
>> drivers/char/hw_random/via-rng.c:38:32: warning: array 'via_rng_cpu_id' assumed to have one element
drivers/char/hw_random/via-rng.c:220:26: warning: 'via_rng_cpu_id' defined but not used [-Wunused-variable]
220 | static struct x86_cpu_id via_rng_cpu_id[] = {
| ^~~~~~~~~~~~~~

vim +/via_rng_cpu_id +38 drivers/char/hw_random/via-rng.c

37
> 38 static const struct x86_cpu_id via_rng_cpu_id[];
39
40
41 enum {
42 VIA_STRFILT_CNT_SHIFT = 16,
43 VIA_STRFILT_FAIL = (1 << 15),
44 VIA_STRFILT_ENABLE = (1 << 14),
45 VIA_RAWBITS_ENABLE = (1 << 13),
46 VIA_RNG_ENABLE = (1 << 6),
47 VIA_NOISESRC1 = (1 << 8),
48 VIA_NOISESRC2 = (1 << 9),
49 VIA_XSTORE_CNT_MASK = 0x0F,
50
51 VIA_RNG_CHUNK_8 = 0x00, /* 64 rand bits, 64 stored bits */
52 VIA_RNG_CHUNK_4 = 0x01, /* 32 rand bits, 32 stored bits */
53 VIA_RNG_CHUNK_4_MASK = 0xFFFFFFFF,
54 VIA_RNG_CHUNK_2 = 0x02, /* 16 rand bits, 32 stored bits */
55 VIA_RNG_CHUNK_2_MASK = 0xFFFF,
56 VIA_RNG_CHUNK_1 = 0x03, /* 8 rand bits, 32 stored bits */
57 VIA_RNG_CHUNK_1_MASK = 0xFF,
58 };
59
60 /*
61 * Investigate using the 'rep' prefix to obtain 32 bits of random data
62 * in one insn. The upside is potentially better performance. The
63 * downside is that the instruction becomes no longer atomic. Due to
64 * this, just like familiar issues with /dev/random itself, the worst
65 * case of a 'rep xstore' could potentially pause a cpu for an
66 * unreasonably long time. In practice, this condition would likely
67 * only occur when the hardware is failing. (or so we hope :))
68 *
69 * Another possible performance boost may come from simply buffering
70 * until we have 4 bytes, thus returning a u32 at a time,
71 * instead of the current u8-at-a-time.
72 *
73 * Padlock instructions can generate a spurious DNA fault, but the
74 * kernel doesn't use CR0.TS, so this doesn't matter.
75 */
76
77 static inline u32 xstore(u32 *addr, u32 edx_in)
78 {
79 u32 eax_out;
80
81 asm(".byte 0x0F,0xA7,0xC0 /* xstore %%edi (addr=%0) */"
82 : "=m" (*addr), "=a" (eax_out), "+d" (edx_in), "+D" (addr));
83
84 return eax_out;
85 }
86
87 static int via_rng_data_present(struct hwrng *rng, int wait)
88 {
89 char buf[16 + PADLOCK_ALIGNMENT - STACK_ALIGN] __attribute__
90 ((aligned(STACK_ALIGN)));
91 u32 *via_rng_datum = (u32 *)PTR_ALIGN(&buf[0], PADLOCK_ALIGNMENT);
92 u32 bytes_out;
93 int i;
94
95 /* We choose the recommended 1-byte-per-instruction RNG rate,
96 * for greater randomness at the expense of speed. Larger
97 * values 2, 4, or 8 bytes-per-instruction yield greater
98 * speed at lesser randomness.
99 *
100 * If you change this to another VIA_CHUNK_n, you must also
101 * change the ->n_bytes values in rng_vendor_ops[] tables.
102 * VIA_CHUNK_8 requires further code changes.
103 *
104 * A copy of MSR_VIA_RNG is placed in eax_out when xstore
105 * completes.
106 */
107
108 for (i = 0; i < 20; i++) {
109 *via_rng_datum = 0; /* paranoia, not really necessary */
110 bytes_out = xstore(via_rng_datum, VIA_RNG_CHUNK_1);
111 bytes_out &= VIA_XSTORE_CNT_MASK;
112 if (bytes_out || !wait)
113 break;
114 udelay(10);
115 }
116 rng->priv = *via_rng_datum;
117 return bytes_out ? 1 : 0;
118 }
119
120 static int via_rng_data_read(struct hwrng *rng, u32 *data)
121 {
122 u32 via_rng_datum = (u32)rng->priv;
123
124 *data = via_rng_datum;
125
126 return 1;
127 }
128
129 static int via_rng_init(struct hwrng *rng)
130 {
131 struct cpuinfo_x86 *c = &cpu_data(0);
132 u32 lo, hi, old_lo;
133
134 /* VIA Nano CPUs don't have the MSR_VIA_RNG anymore. The RNG
135 * is always enabled if CPUID rng_en is set. There is no
136 * RNG configuration like it used to be the case in this
137 * register */
138 if ((c->x86 == 6) && (c->x86_model >= 0x0f)) {
139 if (!boot_cpu_has(X86_FEATURE_XSTORE_EN)) {
140 pr_err(PFX "can't enable hardware RNG "
141 "if XSTORE is not enabled\n");
142 return -ENODEV;
143 }
144 return 0;
145 }
146
147 /* Control the RNG via MSR. Tread lightly and pay very close
148 * attention to values written, as the reserved fields
149 * are documented to be "undefined and unpredictable"; but it
150 * does not say to write them as zero, so I make a guess that
151 * we restore the values we find in the register.
152 */
153 rdmsr(MSR_VIA_RNG, lo, hi);
154
155 old_lo = lo;
156 lo &= ~(0x7f << VIA_STRFILT_CNT_SHIFT);
157 lo &= ~VIA_XSTORE_CNT_MASK;
158 lo &= ~(VIA_STRFILT_ENABLE | VIA_STRFILT_FAIL | VIA_RAWBITS_ENABLE);
159 lo |= VIA_RNG_ENABLE;
160 lo |= VIA_NOISESRC1;
161
162 /* Enable secondary noise source on CPUs where it is present. */
163
164 /* Nehemiah stepping 8 and higher */
165 if ((c->x86_model == 9) && (c->x86_stepping > 7))
166 lo |= VIA_NOISESRC2;
167
168 /* Esther */
169 if (c->x86_model >= 10)
170 lo |= VIA_NOISESRC2;
171
172 if (lo != old_lo)
173 wrmsr(MSR_VIA_RNG, lo, hi);
174
175 /* perhaps-unnecessary sanity check; remove after testing if
176 unneeded */
177 rdmsr(MSR_VIA_RNG, lo, hi);
178 if ((lo & VIA_RNG_ENABLE) == 0) {
179 pr_err(PFX "cannot enable VIA C3 RNG, aborting\n");
180 return -ENODEV;
181 }
182
183 return 0;
184 }
185
186
187 static struct hwrng via_rng = {
188 .name = "via",
189 .init = via_rng_init,
190 .data_present = via_rng_data_present,
191 .data_read = via_rng_data_read,
192 };
193
194
195 static int __init via_rng_mod_init(void)
196 {
197 int err;
198
199 if (!x86_match_cpu(via_rng_cpu_id))
200 return -ENODEV;
201
202 pr_info("VIA RNG detected\n");
203 err = hwrng_register(&via_rng);
204 if (err) {
205 pr_err(PFX "RNG registering failed (%d)\n",
206 err);
207 goto out;
208 }
209 out:
210 return err;
211 }
212 module_init(via_rng_mod_init);
213
214 static void __exit via_rng_mod_exit(void)
215 {
216 hwrng_unregister(&via_rng);
217 }
218 module_exit(via_rng_mod_exit);
219
> 220 static struct x86_cpu_id via_rng_cpu_id[] = {
221 X86_MATCH_VENDOR_FAM_FEATURE(CENTAUR, 6, X86_FEATURE_XSTORE, NULL),
222 {}
223 };
224 MODULE_DEVICE_TABLE(x86cpu, via_rng_cpu_id);
225

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