Re: [Qemu-devel] SMBIOS vs. NUMA (was: Build full type 19 tables)

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 14 Mar 2014 11:14:35 -0400
Gabriel Somlo <gsomlo@gmail.com> wrote:

> On Fri, Mar 14, 2014 at 10:28:30AM +0100, Igor Mammedov wrote:
> > On Thu, 13 Mar 2014 15:01:16 -0400
> > "Gabriel L. Somlo" <gsomlo@gmail.com> wrote:
> > 
> > > On Thu, Mar 13, 2014 at 04:36:12PM +0100, Igor Mammedov wrote:
> > > > 
> > > > After memory hotplug is in I might add e820 entries after above_4g
> > > > for present at boot hotpluggable DIMMDevices. They would have 1:1 mapping
> > > > i.e. t19<-t20<-t17 and belong only to 1 node.
> > > 
> > > Any idea what the max size could be for each one of those ?
> > So far there isn't anything to limit max size of a DEIMMDevice except of
> > allowed max RAM size on QEMU CLI at startup time.
> 
> OK, so then it's more like:
> 
> <-----t19----->
> t20 t20 ... t20
> t17 t17 ... t17
> 
> since t17 is currently limited to 16G. Unless we went to smbios v2.7,
> but that would require lots more external coordination (the bios still
> generates the smbios entry point, where version is recorded). Right
> now that's 2.4.
> 
> More questions about e820: 
> 
> 1. is it safe to assume that E820_RAM (start_addr, size) entries are
> non-overlapping and sorted by increasing start_addr ?
They might overlap, grep for e820_add_entry(). If you interested in
what kernel does with such table look for sanitize_e820_map() there.

Does SMBIOS/t17 actually care about shadowing parts of it by something
else in unrelated e820?

> 
> 2. will there always be a below-4g entry ? if so, will it *and* the
> next entry automatically be assumed to belong to the first node, and
> only subsequently will there be one E820_RAM entry per node (for nodes
> 2, 3, etc) ? 
Once we have DIMMDevices, I'm planning to convert below-4g and above-4g to
a set of DIMMDevices, there will be at least 1 device per node but there could
be more of them to satisfy different backend requirements like hugepage
size, alignment, e.t.c.

BTW why do we care how smbios tables are build in relation to NUMA mapping,
they seem to be totally independent.

> Thanks,
> --Gabriel
> 


-- 
Regards,
  Igor