Re: [PATCH 1/2] x86, msr: add rdmsr_safe_on_cpu_resched() and use it in msr_read()

[kbuild test robot]

Hi Eric,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v4.16-rc5 next-20180316]
[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/Eric-Dumazet/x86-msr-add-rdmsr_safe_on_cpu_resched-and-use-it-in-msr_read/20180319-001007
config: i386-randconfig-x076-201811 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All errors (new ones prefixed by >>):

   arch/x86/kernel/msr.c: In function 'msr_read':
>> arch/x86/kernel/msr.c:63:9: error: implicit declaration of function 'rdmsr_safe_on_cpu_resched'; did you mean 'rdmsr_safe_on_cpu'? [-Werror=implicit-function-declaration]
      err = rdmsr_safe_on_cpu_resched(cpu, reg, &data[0], &data[1]);
            ^~~~~~~~~~~~~~~~~~~~~~~~~
            rdmsr_safe_on_cpu
   Cyclomatic Complexity 1 arch/x86/include/asm/bitops.h:constant_test_bit
   Cyclomatic Complexity 1 arch/x86/include/asm/paravirt.h:paravirt_write_msr_safe
   Cyclomatic Complexity 1 arch/x86/include/asm/msr.h:wrmsr_safe_on_cpu
   Cyclomatic Complexity 1 arch/x86/include/asm/msr.h:rdmsr_safe_regs_on_cpu
   Cyclomatic Complexity 1 arch/x86/include/asm/msr.h:wrmsr_safe_regs_on_cpu
   Cyclomatic Complexity 1 include/linux/err.h:PTR_ERR
   Cyclomatic Complexity 1 include/linux/err.h:IS_ERR
   Cyclomatic Complexity 2 include/linux/err.h:PTR_ERR_OR_ZERO
   Cyclomatic Complexity 1 include/linux/thread_info.h:check_object_size
   Cyclomatic Complexity 2 include/linux/thread_info.h:copy_overflow
   Cyclomatic Complexity 4 include/linux/thread_info.h:check_copy_size
   Cyclomatic Complexity 1 include/linux/fs.h:iminor
   Cyclomatic Complexity 1 include/linux/fs.h:file_inode
   Cyclomatic Complexity 2 include/linux/uaccess.h:copy_from_user
   Cyclomatic Complexity 2 include/linux/uaccess.h:copy_to_user
   Cyclomatic Complexity 1 include/linux/cpuhotplug.h:cpuhp_setup_state
   Cyclomatic Complexity 1 include/linux/cpuhotplug.h:cpuhp_remove_state
   Cyclomatic Complexity 6 arch/x86/kernel/msr.c:msr_write
   Cyclomatic Complexity 11 arch/x86/kernel/msr.c:msr_ioctl
   Cyclomatic Complexity 4 arch/x86/kernel/msr.c:msr_init
   Cyclomatic Complexity 1 arch/x86/kernel/msr.c:msr_exit
   Cyclomatic Complexity 1 arch/x86/kernel/msr.c:msr_device_destroy
   Cyclomatic Complexity 1 arch/x86/kernel/msr.c:msr_device_create
   Cyclomatic Complexity 1 arch/x86/kernel/msr.c:msr_devnode
   Cyclomatic Complexity 4 arch/x86/kernel/msr.c:msr_open
   Cyclomatic Complexity 6 arch/x86/kernel/msr.c:msr_read
   cc1: some warnings being treated as errors

vim +63 arch/x86/kernel/msr.c

    48	
    49	static ssize_t msr_read(struct file *file, char __user *buf,
    50				size_t count, loff_t *ppos)
    51	{
    52		u32 __user *tmp = (u32 __user *) buf;
    53		u32 data[2];
    54		u32 reg = *ppos;
    55		int cpu = iminor(file_inode(file));
    56		int err = 0;
    57		ssize_t bytes = 0;
    58	
    59		if (count % 8)
    60			return -EINVAL;	/* Invalid chunk size */
    61	
    62		for (; count; count -= 8) {
  > 63			err = rdmsr_safe_on_cpu_resched(cpu, reg, &data[0], &data[1]);
    64			if (err)
    65				break;
    66			if (copy_to_user(tmp, &data, 8)) {
    67				err = -EFAULT;
    68				break;
    69			}
    70			tmp += 2;
    71			bytes += 8;
    72		}
    73	
    74		return bytes ? bytes : err;
    75	}
    76	

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