[PATCH 5/5] cpu: Introduce getHost supoort for ARM

Daniel P. Berrangé berrange at redhat.com
Mon Mar 30 12:26:56 UTC 2020


Re-adding libvir-list to the CC line.

On Mon, Mar 30, 2020 at 08:20:44PM +0800, Zhenyu Zheng wrote:
> Hi, yes, I think we can do that using  inline assembly, I can check it out
> if you think it is a better solution,
> do you have any suggestions for the features(cpu flags) part? It seems that
> ARM does not have a location/register
> that holds all the flags, seems that we have to query alot of different
> registers to check for features, which could
> be quite messy.

Perhaps there is a way to record the location/register info in the XML
against each feature name, so that the code itself can stay simple and
just be driven from the metadata ?

I'm not familiar enough with Arm to know how feasiable this is though,
so will have to leave that to others to give an opinion.

> 
> On Mon, Mar 30, 2020 at 8:01 PM Daniel P. Berrangé <berrange at redhat.com>
> wrote:
> 
> > On Mon, Mar 30, 2020 at 07:32:36PM +0800, Zhenyu Zheng wrote:
> > > Hi Daniel,
> > >
> > > Thanks for thre review and reply, my first implementation was going to
> > > gather data from /proc/cpuinfo, but unlike X86, we can only get this kind
> > > of info:
> > >
> > >   processor       : 0
> > >   BogoMIPS        : 200.00
> > >   Features        : fp asimd evtstrm aes pmull sha1 sha2 crc32 cpuid
> > >   CPU implementer : 0x43
> > >   CPU architecture: 8
> > >   CPU variant     : 0x1
> > >   CPU part        : 0x0a1
> > >   CPU revision    : 1
> > >
> > > so we have to perform some translation to perform human readable
> > > information, and I mentioned that 'lscpu' has done that too. So Andrea
> > > Bolognani
> > > suggested that maybe we can use it directly, to avoid re-implement the
> > > translation. Here is the discussion:
> > > https://www.redhat.com/archives/libvir-list/2020-March/msg00812.html
> >
> > On x86 we get majority of info straight from calling the CPUID instruction,
> > not /proc/cpuinfo, and use our XML data files in src/cpu_map to translate
> > things into human readable names.  I see you're adding XML data files
> > with names in the earlier patches. Is it possible to add the hex values
> > for the CPU implementer/architecture/variant/part to these XML files so
> > we can directly map them in libvirt, in the same way we do for x86

Regards,
Daniel
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