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Re: [Qemu-devel] [PATCH 33/35] pc: ACPI BIOS: reserve SRAT entry for hot


From: Hu Tao
Subject: Re: [Qemu-devel] [PATCH 33/35] pc: ACPI BIOS: reserve SRAT entry for hotplug mem hole
Date: Tue, 15 Apr 2014 14:37:01 +0800
User-agent: Mutt/1.5.21 (2010-09-15)

On Mon, Apr 14, 2014 at 06:44:42PM +0200, Igor Mammedov wrote:
> On Mon, 14 Apr 2014 15:25:01 +0800
> Hu Tao <address@hidden> wrote:
> 
> > On Fri, Apr 04, 2014 at 03:36:58PM +0200, Igor Mammedov wrote:
> > > Needed for Windows to use hotplugged memory device, otherwise
> > > it complains that server is not configured for memory hotplug.
> > > Tests shows that aftewards it uses dynamically provided
> > > proximity value from _PXM() method if available.
> > > 
> > > Signed-off-by: Igor Mammedov <address@hidden>
> > > ---
> > >  hw/i386/acpi-build.c | 14 ++++++++++++++
> > >  1 file changed, 14 insertions(+)
> > > 
> > > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> > > index ef89e99..012b100 100644
> > > --- a/hw/i386/acpi-build.c
> > > +++ b/hw/i386/acpi-build.c
> > > @@ -1197,6 +1197,8 @@ build_srat(GArray *table_data, GArray *linker,
> > >      uint64_t curnode;
> > >      int srat_start, numa_start, slots;
> > >      uint64_t mem_len, mem_base, next_base;
> > > +    PCMachineState *pcms = PC_MACHINE(qdev_get_machine());
> > > +    ram_addr_t hotplug_as_size = 
> > > memory_region_size(&pcms->hotplug_memory);
> > >  
> > >      srat_start = table_data->len;
> > >  
> > > @@ -1261,6 +1263,18 @@ build_srat(GArray *table_data, GArray *linker,
> > >          acpi_build_srat_memory(numamem, 0, 0, 0, MEM_AFFINITY_NOFLAGS);
> > >      }
> > >  
> > > +    /*
> > > +     * Fake entry required by Windows to enable memory hotplug in OS.
> > > +     * Individual DIMM devices override proximity set here via _PXM 
> > > method,
> > > +     * which returns associated with it NUMA node id.
> > > +     */
> > > +    if (hotplug_as_size) {
> > > +        numamem = acpi_data_push(table_data, sizeof *numamem);
> > > +        acpi_build_srat_memory(numamem, pcms->hotplug_memory_base,
> > > +                               hotplug_as_size, 0, 
> > > MEM_AFFINITY_HOTPLUGGABLE |
> > > +                               MEM_AFFINITY_ENABLED);
> > > +    }
> > > +
> > 
> > Hi Igor,
> > 
> > With the faked entry, memory unplug doesn't work. Entries should be set
> > up for each node with correct flags(enable, hotpluggable) to make memory
> > unplug work.
> Could you be more specific, what and how doesn't work and why there is
> need for SRAT entries per DIMM?
> I've briefly tested with your unplug patches and linux seemed be ok with 
> unplug,
> i.e. device node was removed from /sys after receiving remove notification.


Following are fail cases:

------------------------------------------------------------------------+----------------------------------------------
guest commands                                                          | this 
patch                    | hacked SRAT
------------------------------------------------------------------------+----------------------------------------------
echo 'online' > /sys/devices/system/memory/memory32/state && \          |       
                        |
echo 'offline' > /sys/devices/system/memory/memory32/state              |  fail 
                        | success 
------------------------------------------------------------------------+----------------------------------------------
echo 'online' > /sys/devices/system/memory/memory32/state && \          |       
                        |
echo 1 > /sys/devices/LNXSYSTM\:00/device\:00/PNP0C80\:00/eject         |  fail 
                        | success
------------------------------------------------------------------------+----------------------------------------------
echo 'online_movable' > /sys/devices/system/memory/memory32/state       |  
fail[first memory block]     | fail
------------------------------------------------------------------------+----------------------------------------------
echo 'online_movable' > /sys/devices/system/memory/memory35/state && \  |       
                        |
echo 'offline' > /sys/devices/system/memory/memory35/state              |  
success[last memory block]   | success
------------------------------------------------------------------------+----------------------------------------------
echo 'online_movable' > /sys/devices/system/memory/memory32/state && \  |       
                        |
echo 1 > /sys/devices/LNXSYSTM\:00/device\:00/PNP0C80\:00/eject         |  
success[last memory block]   | success
------------------------------------------------------------------------+----------------------------------------------

Hacke SRAT memory entry:

PXM: 0
range: 4G ~ 4G + 512M
flags: Enabled Hot-Pluggable

PXM: 1
range: 4G + 512M ~ 5G
flags: Enabled Hot-Pluggable

So I think we should add maxmem to -numa and build SRAT accordingly.
But there is something I'm not sure with. I added dimm in node 1, but
it's memory range fell in node 0. Users always can cause the mismatch
with dimm,start,node.



This is the relevent part in command line:

qemu command line: -m 512M,slots=4,maxmem=2G \
                   -object memory-ram,id=foo,size=512M \
                   -numa node,id=n0,mem=256M -numa node,id=n1,mem=256M 

(qemu monitor) device_add dimm,id=d0,memdev=foo,node=1

> 
> > 
> > Windows has not been tested yet. I encountered a problem that there is
> > no SRAT in Windows so even memory hotplug doesn't work. (but there is
> > in Linux with the same configuration).
> For Windows to work one needs to add "-numa node" CLI option so that
> SRAT would be exposed to guest.

Thanks. I need to double-check.

> Paolo suggested to enable -numa node by default, I guess we can do it
> once NUMA re-factoring is merged.
> 
> That said, I haven't found any information that Windows supports
> memory hot-remove. Google tells that only hot-add is supported
> for up to WS2008R2. I've tested WS2012R2, it doesn't work either,
> i.e. it sees but ignores Notify request.
> 
> > 
> > Regards,
> > Hu Tao
> > 

Attachment: SRAT.dsl
Description: Text document

Attachment: SRAT.dsl.new
Description: Text document


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