Re: [PATCH] x86: clean up confusing x86_mask

[kbuild test robot <lkp@intel.com>]

Hi Jia,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on v4.15-rc5]
[also build test WARNING on next-20171222]
[cannot apply to tip/x86/core]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Jia-Zhang/x86-clean-up-confusing-x86_mask/20171231-182946
reproduce:
        # apt-get install sparse
        make ARCH=x86_64 allmodconfig
        make C=1 CF=-D__CHECK_ENDIAN__


sparse warnings: (new ones prefixed by >>)


vim +165 drivers/char/hw_random/via-rng.c

135233635 Michael Buesch  2006-06-26  128  
135233635 Michael Buesch  2006-06-26  129  static int via_rng_init(struct hwrng *rng)
135233635 Michael Buesch  2006-06-26  130  {
11025e855 Dave Jones      2008-02-06  131  	struct cpuinfo_x86 *c = &cpu_data(0);
135233635 Michael Buesch  2006-06-26  132  	u32 lo, hi, old_lo;
135233635 Michael Buesch  2006-06-26  133  
858576bdc Harald Welte    2009-05-15  134  	/* VIA Nano CPUs don't have the MSR_VIA_RNG anymore.  The RNG
858576bdc Harald Welte    2009-05-15  135  	 * is always enabled if CPUID rng_en is set.  There is no
858576bdc Harald Welte    2009-05-15  136  	 * RNG configuration like it used to be the case in this
858576bdc Harald Welte    2009-05-15  137  	 * register */
858576bdc Harald Welte    2009-05-15  138  	if ((c->x86 == 6) && (c->x86_model >= 0x0f)) {
362f924b6 Borislav Petkov 2015-12-07  139  		if (!boot_cpu_has(X86_FEATURE_XSTORE_EN)) {
7a1ae9c0c Sudip Mukherjee 2014-09-15  140  			pr_err(PFX "can't enable hardware RNG "
858576bdc Harald Welte    2009-05-15  141  				"if XSTORE is not enabled\n");
858576bdc Harald Welte    2009-05-15  142  			return -ENODEV;
858576bdc Harald Welte    2009-05-15  143  		}
858576bdc Harald Welte    2009-05-15  144  		return 0;
858576bdc Harald Welte    2009-05-15  145  	}
858576bdc Harald Welte    2009-05-15  146  
135233635 Michael Buesch  2006-06-26  147  	/* Control the RNG via MSR.  Tread lightly and pay very close
135233635 Michael Buesch  2006-06-26  148  	 * close attention to values written, as the reserved fields
135233635 Michael Buesch  2006-06-26  149  	 * are documented to be "undefined and unpredictable"; but it
135233635 Michael Buesch  2006-06-26  150  	 * does not say to write them as zero, so I make a guess that
135233635 Michael Buesch  2006-06-26  151  	 * we restore the values we find in the register.
135233635 Michael Buesch  2006-06-26  152  	 */
135233635 Michael Buesch  2006-06-26  153  	rdmsr(MSR_VIA_RNG, lo, hi);
135233635 Michael Buesch  2006-06-26  154  
135233635 Michael Buesch  2006-06-26  155  	old_lo = lo;
135233635 Michael Buesch  2006-06-26  156  	lo &= ~(0x7f << VIA_STRFILT_CNT_SHIFT);
135233635 Michael Buesch  2006-06-26  157  	lo &= ~VIA_XSTORE_CNT_MASK;
135233635 Michael Buesch  2006-06-26  158  	lo &= ~(VIA_STRFILT_ENABLE | VIA_STRFILT_FAIL | VIA_RAWBITS_ENABLE);
135233635 Michael Buesch  2006-06-26  159  	lo |= VIA_RNG_ENABLE;
11025e855 Dave Jones      2008-02-06  160  	lo |= VIA_NOISESRC1;
11025e855 Dave Jones      2008-02-06  161  
11025e855 Dave Jones      2008-02-06  162  	/* Enable secondary noise source on CPUs where it is present. */
11025e855 Dave Jones      2008-02-06  163  
11025e855 Dave Jones      2008-02-06  164  	/* Nehemiah stepping 8 and higher */
11025e855 Dave Jones      2008-02-06 @165  	if ((c->x86_model == 9) && (c->x86_mask > 7))
11025e855 Dave Jones      2008-02-06  166  		lo |= VIA_NOISESRC2;
11025e855 Dave Jones      2008-02-06  167  
11025e855 Dave Jones      2008-02-06  168  	/* Esther */
11025e855 Dave Jones      2008-02-06  169  	if (c->x86_model >= 10)
11025e855 Dave Jones      2008-02-06  170  		lo |= VIA_NOISESRC2;
135233635 Michael Buesch  2006-06-26  171  
135233635 Michael Buesch  2006-06-26  172  	if (lo != old_lo)
135233635 Michael Buesch  2006-06-26  173  		wrmsr(MSR_VIA_RNG, lo, hi);
135233635 Michael Buesch  2006-06-26  174  
135233635 Michael Buesch  2006-06-26  175  	/* perhaps-unnecessary sanity check; remove after testing if
135233635 Michael Buesch  2006-06-26  176  	   unneeded */
135233635 Michael Buesch  2006-06-26  177  	rdmsr(MSR_VIA_RNG, lo, hi);
135233635 Michael Buesch  2006-06-26  178  	if ((lo & VIA_RNG_ENABLE) == 0) {
7a1ae9c0c Sudip Mukherjee 2014-09-15  179  		pr_err(PFX "cannot enable VIA C3 RNG, aborting\n");
135233635 Michael Buesch  2006-06-26  180  		return -ENODEV;
135233635 Michael Buesch  2006-06-26  181  	}
135233635 Michael Buesch  2006-06-26  182  
135233635 Michael Buesch  2006-06-26  183  	return 0;
135233635 Michael Buesch  2006-06-26  184  }
135233635 Michael Buesch  2006-06-26  185  

:::::: The code at line 165 was first introduced by commit
:::::: 11025e855235144271a0e447e3650b203f8215f4 via-rng: enable secondary noise source on CPUs where it is present

:::::: TO: Dave Jones <davej@redhat.com>
:::::: CC: Linus Torvalds <torvalds@woody.linux-foundation.org>

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