[libvirt] [PATCH 2/5] util: introduce virHostCPUGetMicrocodeVersion

[Peter Krempa]

On Thu, Jan 04, 2018 at 15:58:09 +0100, Jiri Denemark wrote:
> From: Paolo Bonzini <pbonzini at redhat.com>
> 
> This new API reads host's CPU microcode version from /proc/cpuinfo.
> 
> Unfortunately, there is no other way of reading microcode version which
> would be usable from both system and session daemon.
> 
> Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
> Signed-off-by: Jiri Denemark <jdenemar at redhat.com>
> ---
>  src/libvirt_private.syms |  1 +
>  src/util/virhostcpu.c    | 43 +++++++++++++++++++++++++++++++++++++++++++
>  src/util/virhostcpu.h    |  2 ++
>  3 files changed, 46 insertions(+)
> 
> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
> index 8d583e3e74..a705fa846d 100644
> --- a/src/libvirt_private.syms
> +++ b/src/libvirt_private.syms
> @@ -1869,6 +1869,7 @@ virHostCPUGetCount;
>  virHostCPUGetInfo;
>  virHostCPUGetKVMMaxVCPUs;
>  virHostCPUGetMap;
> +virHostCPUGetMicrocodeVersion;
>  virHostCPUGetOnline;
>  virHostCPUGetOnlineBitmap;
>  virHostCPUGetPresentBitmap;
> diff --git a/src/util/virhostcpu.c b/src/util/virhostcpu.c
> index c485a97211..713fdec553 100644
> --- a/src/util/virhostcpu.c
> +++ b/src/util/virhostcpu.c
> @@ -1206,3 +1206,46 @@ virHostCPUGetKVMMaxVCPUs(void)
>      return -1;
>  }
>  #endif /* HAVE_LINUX_KVM_H */
> +
> +
> +#ifdef __linux__
> +
> +unsigned int
> +virHostCPUGetMicrocodeVersion(void)
> +{
> +    char *outbuf = NULL;
> +    char *cur;
> +    unsigned int version = 0;
> +
> +    if (virFileReadHeaderQuiet(CPUINFO_PATH, 4096, &outbuf) < 0) {

In other places we read 1MiB of /proc/cpuinfo:

src/util/virsysinfo.c:#define CPUINFO_FILE_LEN (1024*1024)    /* 1MB limit for /proc/cpuinfo file */

Will this be enough?


> +        char ebuf[1024];
> +        VIR_DEBUG("Failed to read microcode version from %s: %s",
> +                  CPUINFO_PATH, virStrerror(errno, ebuf, sizeof(ebuf)));

Formatting the error message into a debug message does not make much
sense. I'd just log 'errno' in raw since this function does not really
return any errors.

> +        return 0;
> +    }
> +
> +    /* Account for format 'microcode    : XXXX'*/
> +    if (!(cur = strstr(outbuf, "microcode")) ||
> +        !(cur = strchr(cur, ':')))
> +        goto cleanup;
> +    cur++;
> +
> +    /* Linux places the microcode revision in a 32-bit integer, so
> +     * ui is fine for us too.  */
> +    if (virStrToLong_ui(cur, &cur, 0, &version) < 0)
> +        goto cleanup;
> +
> + cleanup:
> +    VIR_FREE(outbuf);
> +    return version;
> +}
> +
> +#else

#else /* __linux__ */

> +
> +unsigned int
> +virHostCPUGetMicrocodeVersion(void)
> +{
> +    return 0;
> +}
> +
> +#endif

#endif /* __linux__ */

> diff --git a/src/util/virhostcpu.h b/src/util/virhostcpu.h
> index 67033de842..f9f3359288 100644
> --- a/src/util/virhostcpu.h
> +++ b/src/util/virhostcpu.h
> @@ -66,4 +66,6 @@ virBitmapPtr virHostCPUGetSiblingsList(unsigned int cpu);
>  
>  int virHostCPUGetOnline(unsigned int cpu, bool *online);
>  
> +unsigned int virHostCPUGetMicrocodeVersion(void);
> +
>  #endif /* __VIR_HOSTCPU_H__*/

ACK with pointless error formatting removed.

> -- 
> 2.15.1
> 
> --
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