Re: [Qemu-devel] [PATCH] x86/acpi: build SRAT when memory hotplug is enabled

[Dou Liyang]

Hi Eduardo,

At 09/04/2017 09:08 PM, Eduardo Habkost wrote:
[...]
> > In my opinion, this may also add the hotpluggable memory, and see the
> > following commemts.
> >
> >     /*
> >      * Entry is required for Windows to enable memory hotplug in OS
> >      * and for Linux to enable SWIOTLB when booted with less than
> >            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >      * 4G of RAM. Windows works better if the entry sets proximity
> >      * to the highest NUMA node in the machine.
> >      * Memory devices may override proximity set by this entry,
> >      * providing _PXM method if necessary.
> >      */
> >     if (hotplugabble_address_space_size) {
> >         numamem = acpi_data_push(table_data, sizeof *numamem);
> >         build_srat_memory(numamem, pcms->hotplug_memory.base,
> >                           hotplugabble_address_space_size, pcms->numa_nodes
> > - 1,
> >                           MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> >     }
>
> You are correct, I didn't see that part of the code.  If that's
> the entry that's missing, the patch makes sense.  Thanks!
>
> However, the resulting tables still don't look correct: it will
> generate an entry assigned to NUMA node (uint32_t)-1 if no NUMA
> nodes are configured elsewhere, some APIC entries, but no entries
> for the rest of the memory.

Yes, indeed.

> Igor's suggestion to enable NUMA implicitly sounds safer to me.

I agree with Igor too.

Is anybody doing this? If not, may I make a patch to enable adding NUMA
node implicitly first. let's see what it looks like.

Thanks,
        dou.