diff mbox series

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

Message ID 20231225025330.809554-1-LeoLiu-oc@zhaoxin.com (mailing list archive)
State Superseded
Delegated to: Herbert Xu
Headers show
Series [v4] hwrng: add Zhaoxin rng driver base on rep_xstore instruction | expand

Commit Message

LeoLiu-oc Dec. 25, 2023, 2:53 a.m. UTC
From: LeoLiuoc <LeoLiu-oc@zhaoxin.com>

Add support for Zhaoxin hardware random number generator.
This driver base on rep_xstore instruction and uses the same
X86_FEATURE_XSTORE as via-rng driver. Therefore, modify the x86_cpu_id
array in the via-rng driver, so that the corresponding driver can be
correctly loader on respective platforms.

v1 -> v2:
1. Fix assembler code errors
2. Remove redundant CPU model check codes

v2 -> v3:
1. Optimize code details based on the kernel style

v3 -> v4:
1. Fix a typographical error

Signed-off-by: LeoLiuoc <LeoLiu-oc@zhaoxin.com>
---
 drivers/char/hw_random/Kconfig       | 12 ++++
 drivers/char/hw_random/Makefile      |  1 +
 drivers/char/hw_random/via-rng.c     | 10 +--
 drivers/char/hw_random/zhaoxin-rng.c | 95 ++++++++++++++++++++++++++++
 4 files changed, 113 insertions(+), 5 deletions(-)
 create mode 100644 drivers/char/hw_random/zhaoxin-rng.c

Comments

kernel test robot Dec. 26, 2023, 12:54 a.m. UTC | #1
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
kernel test robot Dec. 26, 2023, 1:04 a.m. UTC | #2
Hi LeoLiu-oc,

kernel test robot noticed the following build errors:

[auto build test ERROR on char-misc/char-misc-testing]
[also build test ERROR 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-rhel-8.3 (https://download.01.org/0day-ci/archive/20231226/202312260844.FPx3YOsI-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/20231226/202312260844.FPx3YOsI-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/202312260844.FPx3YOsI-lkp@intel.com/

All errors (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


vim +220 drivers/char/hw_random/via-rng.c

   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
kernel test robot Dec. 26, 2023, 7:49 a.m. UTC | #3
Hi LeoLiu-oc,

kernel test robot noticed the following build errors:

[auto build test ERROR on char-misc/char-misc-testing]
[also build test ERROR 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: i386-randconfig-141-20231225 (https://download.01.org/0day-ci/archive/20231226/202312261505.rDaQJwAq-lkp@intel.com/config)
compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231226/202312261505.rDaQJwAq-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/202312261505.rDaQJwAq-lkp@intel.com/

All errors (new ones prefixed by >>):

>> drivers/char/hw_random/via-rng.c:220:26: error: redefinition of 'via_rng_cpu_id' with a different type: 'struct x86_cpu_id[]' vs 'const struct x86_cpu_id[]'
   static struct x86_cpu_id via_rng_cpu_id[] = {
                            ^
   drivers/char/hw_random/via-rng.c:38:32: note: previous definition is here
   static const struct x86_cpu_id via_rng_cpu_id[];
                                  ^
>> drivers/char/hw_random/via-rng.c:224:1: error: definition of variable with array type needs an explicit size or an initializer
   MODULE_DEVICE_TABLE(x86cpu, via_rng_cpu_id);
   ^
   include/linux/module.h:244:21: note: expanded from macro 'MODULE_DEVICE_TABLE'
   extern typeof(name) __mod_##type##__##name##_device_table               \
                       ^
   <scratch space>:56:1: note: expanded from here
   __mod_x86cpu__via_rng_cpu_id_device_table
   ^
   drivers/char/hw_random/via-rng.c:38:32: warning: tentative array definition assumed to have one element
   static const struct x86_cpu_id via_rng_cpu_id[];
                                  ^
   1 warning and 2 errors generated.


vim +220 drivers/char/hw_random/via-rng.c

   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
diff mbox series

Patch

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index 442c40efb200..3c1c4fa1203c 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -152,6 +152,18 @@  config HW_RANDOM_VIA
 
 	  If unsure, say Y.
 
+config HW_RANDOM_ZHAOXIN
+	tristate "Zhaoxin HW Random Number Generator support"
+	depends on X86
+	help
+	  This driver provides kernel-side support for the Random Number
+	  Generator hardware found on Zhaoxin based motherboards.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called zhaoxin-rng.
+
+	  If unsure, say Y.
+
 config HW_RANDOM_IXP4XX
 	tristate "Intel IXP4xx NPU HW Pseudo-Random Number Generator support"
 	depends on ARCH_IXP4XX || COMPILE_TEST
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index 32549a1186dc..ef5b3ae0794d 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -14,6 +14,7 @@  obj-$(CONFIG_HW_RANDOM_GEODE) += geode-rng.o
 obj-$(CONFIG_HW_RANDOM_N2RNG) += n2-rng.o
 n2-rng-y := n2-drv.o n2-asm.o
 obj-$(CONFIG_HW_RANDOM_VIA) += via-rng.o
+obj-$(CONFIG_HW_RANDOM_ZHAOXIN) += zhaoxin-rng.o
 obj-$(CONFIG_HW_RANDOM_EXYNOS) += exynos-trng.o
 obj-$(CONFIG_HW_RANDOM_IXP4XX) += ixp4xx-rng.o
 obj-$(CONFIG_HW_RANDOM_OMAP) += omap-rng.o
diff --git a/drivers/char/hw_random/via-rng.c b/drivers/char/hw_random/via-rng.c
index a9a0a3b09c8b..9f7da031adc4 100644
--- a/drivers/char/hw_random/via-rng.c
+++ b/drivers/char/hw_random/via-rng.c
@@ -35,7 +35,7 @@ 
 #include <asm/cpufeature.h>
 #include <asm/fpu/api.h>
 
-
+static const struct x86_cpu_id via_rng_cpu_id[];
 
 
 enum {
@@ -135,7 +135,7 @@  static int via_rng_init(struct hwrng *rng)
 	 * is always enabled if CPUID rng_en is set.  There is no
 	 * RNG configuration like it used to be the case in this
 	 * register */
-	if (((c->x86 == 6) && (c->x86_model >= 0x0f))  || (c->x86 > 6)){
+	if ((c->x86 == 6) && (c->x86_model >= 0x0f)) {
 		if (!boot_cpu_has(X86_FEATURE_XSTORE_EN)) {
 			pr_err(PFX "can't enable hardware RNG "
 				"if XSTORE is not enabled\n");
@@ -196,7 +196,7 @@  static int __init via_rng_mod_init(void)
 {
 	int err;
 
-	if (!boot_cpu_has(X86_FEATURE_XSTORE))
+	if (!x86_match_cpu(via_rng_cpu_id))
 		return -ENODEV;
 
 	pr_info("VIA RNG detected\n");
@@ -217,8 +217,8 @@  static void __exit via_rng_mod_exit(void)
 }
 module_exit(via_rng_mod_exit);
 
-static struct x86_cpu_id __maybe_unused via_rng_cpu_id[] = {
-	X86_MATCH_FEATURE(X86_FEATURE_XSTORE, NULL),
+static struct x86_cpu_id via_rng_cpu_id[] = {
+	X86_MATCH_VENDOR_FAM_FEATURE(CENTAUR, 6, X86_FEATURE_XSTORE, NULL),
 	{}
 };
 MODULE_DEVICE_TABLE(x86cpu, via_rng_cpu_id);
diff --git a/drivers/char/hw_random/zhaoxin-rng.c b/drivers/char/hw_random/zhaoxin-rng.c
new file mode 100644
index 000000000000..3e5770df9948
--- /dev/null
+++ b/drivers/char/hw_random/zhaoxin-rng.c
@@ -0,0 +1,95 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * RNG driver for Zhaoxin RNGs
+ *
+ * Copyright 2023 (c) Zhaoxin Semiconductor Co., Ltd
+ */
+
+#include <asm/cpu_device_id.h>
+#include <asm/fpu/api.h>
+#include <crypto/padlock.h>
+#include <linux/cpufeature.h>
+#include <linux/delay.h>
+#include <linux/hw_random.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+enum {
+	ZHAOXIN_RNG_CHUNK_8		= 0x00, /* 64 rand bits, 64 stored bits */
+	ZHAOXIN_RNG_CHUNK_4		= 0x01, /* 32 rand bits, 32 stored bits */
+	ZHAOXIN_RNG_CHUNK_2		= 0x02, /* 16 rand bits, 32 stored bits */
+	ZHAOXIN_RNG_CHUNK_1		= 0x03, /*  8 rand bits, 32 stored bits */
+	ZHAOXIN_RNG_MAX_SIZE	= (128 * 1024),
+};
+
+static int zhaoxin_rng_init(struct hwrng *rng)
+{
+	if (!boot_cpu_has(X86_FEATURE_XSTORE_EN)) {
+		pr_err(PFX "can't enable hardware RNG if XSTORE is not enabled\n");
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+static inline int rep_xstore(size_t size, size_t factor, void *result)
+{
+	asm(".byte 0xf3, 0x0f, 0xa7, 0xc0"
+		: "=m"(*(size_t *)result), "+c"(size), "+d"(factor), "+D"(result));
+
+	return 0;
+}
+
+static int zhaoxin_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
+{
+	if (max > ZHAOXIN_RNG_MAX_SIZE)
+		max = ZHAOXIN_RNG_MAX_SIZE;
+
+	rep_xstore(max, ZHAOXIN_RNG_CHUNK_1, data);
+
+	return max;
+}
+
+static struct hwrng zhaoxin_rng = {
+	.name = "zhaoxin",
+	.init = zhaoxin_rng_init,
+	.read = zhaoxin_rng_read,
+};
+
+static const struct x86_cpu_id zhaoxin_rng_cpu_ids[] = {
+	X86_MATCH_VENDOR_FAM_FEATURE(ZHAOXIN, 6, X86_FEATURE_XSTORE, NULL),
+	X86_MATCH_VENDOR_FAM_FEATURE(ZHAOXIN, 7, X86_FEATURE_XSTORE, NULL),
+	X86_MATCH_VENDOR_FAM_FEATURE(CENTAUR, 7, X86_FEATURE_XSTORE, NULL),
+	{}
+};
+MODULE_DEVICE_TABLE(x86cpu, zhaoxin_rng_cpu_ids);
+
+static int __init zhaoxin_rng_mod_init(void)
+{
+	int err;
+
+	if (!x86_match_cpu(zhaoxin_rng_cpu_ids)) {
+		pr_err(PFX "The CPU isn't support XSTORE.\n");
+		return -ENODEV;
+	}
+
+	pr_info("Zhaoxin RNG detected\n");
+
+	err = hwrng_register(&zhaoxin_rng);
+	if (err)
+		pr_err(PFX "RNG registering failed (%d)\n", err);
+
+	return err;
+}
+module_init(zhaoxin_rng_mod_init);
+
+static void __exit zhaoxin_rng_mod_exit(void)
+{
+	hwrng_unregister(&zhaoxin_rng);
+}
+module_exit(zhaoxin_rng_mod_exit);
+
+MODULE_DESCRIPTION("H/W RNG driver for Zhaoxin CPUs");
+MODULE_AUTHOR("YunShen@zhaoxin.com");
+MODULE_LICENSE("GPL");