Re: [Qemu-devel] [RFC PATCH v2 2/3] utils: Add cpuinfo helper to fetch /proc/cpuinfo

[Vijay Kilari]

On Thu, Apr 7, 2016 at 3:41 PM, Peter Maydell <address@hidden> wrote:
> On 7 April 2016 at 10:58,  <address@hidden> wrote:
>> From: Vijaya Kumar K <address@hidden>
>>
>> utils cannot read target cpu information to
>> fetch cpu information to implement cpu specific
>> features or erratas. For this parse /proc/cpuinfo
>> and fetch cpu information.
>>
>> For now this helper only fetches cpu information
>> for arm architectures.
>
> As I understand it /proc/cpuinfo is intended only for
> humans to read. Please don't write code to parse it;
> find a different way to get this information instead
> if you really need it.

  The utils code does not accept any dependency with target specific code.
The libqemuutil.a is compiled and linked before target specific
code is compiled.

  Also, utils functions neither have any cpu object to fetch
cpu identification information (ex: midr in case of arm) to identify the
cpu information nor utils cannot make any ioctl to read cpu information
from qemu.

Also unlike x86 there is no cpuid.h where we can get cpu identification
information for arm64.

So, I think userspace process can rely on /proc/cpuinfo for
fetching cpu information.

>
> (I'm not really happy about such specific-to-a-particular-vendor
> patches in QEMU anyway; we should have migration code that
> works acceptably for any implementation.)
>
> thanks
> -- PMM