On Thu, Mar 16, 2017 at 04:38:24PM +0800, He Chen wrote:
> Current, QEMU does not provide a clear command to set vNUMA distance for
> guest although we already have `-numa` command to set vNUMA nodes.
>
> vNUMA distance makes sense in certain scenario.
> But now, if we create a guest that has 4 vNUMA nodes, when we check NUMA
> info via `numactl -H`, we will see:
>
> node distance:
> node 0 1 2 3
> 0: 10 20 20 20
> 1: 20 10 20 20
> 2: 20 20 10 20
> 3: 20 20 20 10
>
> Guest kernel regards all local node as distance 10, and all remote node
> as distance 20 when there is no SLIT table since QEMU doesn't build it.
> It looks like a little strange when you have seen the distance in an
> actual physical machine that contains 4 NUMA nodes. My machine shows:
>
> node distance:
> node 0 1 2 3
> 0: 10 21 31 41
> 1: 21 10 21 31
> 2: 31 21 10 21
> 3: 41 31 21 10
>
> To set vNUMA distance, guest should see a complete SLIT table.
> I found QEMU has provide `-acpitable` command that allows users to add
> a ACPI table into guest, but it requires users building ACPI table by
> themselves first. Using `-acpitable` to add a SLIT table may be not so
> straightforward or flexible, imagine that when the vNUMA configuration
> is changes and we need to generate another SLIT table manually. It may
> not be friendly to users or upper software like libvirt.
>
> This patch is going to add SLIT table support in QEMU, and provides
> additional option `dist` for command `-numa` to allow user set vNUMA
> distance by QEMU command.
>
> With this patch, when a user wants to create a guest that contains
> several vNUMA nodes and also wants to set distance among those nodes,
> the QEMU command would like:
>
> ```
> -object
> memory-backend-ram,size=1G,prealloc=yes,host-nodes=0,policy=bind,id=node0 \
> -numa node,nodeid=0,cpus=0,memdev=node0 \
> -object
> memory-backend-ram,size=1G,prealloc=yes,host-nodes=1,policy=bind,id=node1 \
> -numa node,nodeid=1,cpus=1,memdev=node1 \
> -object
> memory-backend-ram,size=1G,prealloc=yes,host-nodes=2,policy=bind,id=node2 \
> -numa node,nodeid=2,cpus=2,memdev=node2 \
> -object
> memory-backend-ram,size=1G,prealloc=yes,host-nodes=3,policy=bind,id=node3 \
> -numa node,nodeid=3,cpus=3,memdev=node3 \
> -numa dist,src=0,dst=1,val=21 \
> -numa dist,src=0,dst=2,val=31 \
> -numa dist,src=0,dst=3,val=41 \
> -numa dist,src=1,dst=0,val=21 \
> ...
> ```
>
> Signed-off-by: He Chen <he.c...@linux.intel.com>
> ---
> hw/i386/acpi-build.c | 27 +++++++++++++++++++++++++++
> include/sysemu/numa.h | 1 +
> include/sysemu/sysemu.h | 3 +++
> numa.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
> qapi-schema.json | 24 ++++++++++++++++++++++--
> qemu-options.hx | 12 +++++++++++-
> 6 files changed, 108 insertions(+), 3 deletions(-)
>
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index 2073108..50906b9 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -2395,6 +2395,31 @@ build_srat(GArray *table_data, BIOSLinker *linker,
> MachineState *machine)
> table_data->len - srat_start, 1, NULL, NULL);
> }
>
> +/*
> + * ACPI spec 5.2.17 System Locality Distance Information Table
> + * (Revision 2.0 or later)
> + */
> +static void
> +build_slit(GArray *table_data, BIOSLinker *linker, MachineState *machine)
> +{
> + int slit_start, i, j;
> + slit_start = table_data->len;
> +
> + acpi_data_push(table_data, sizeof(AcpiTableHeader));
> +
> + build_append_int_noprefix(table_data, nb_numa_nodes, 8);
> + for (i = 0; i < nb_numa_nodes; i++) {
> + for (j = 0; j < nb_numa_nodes; j++) {
> + build_append_int_noprefix(table_data, numa_info[i].distance[j],
> 1);
> + }
> + }
> +
> + build_header(linker, table_data,
> + (void *)(table_data->data + slit_start),
> + "SLIT",
> + table_data->len - slit_start, 1, NULL, NULL);
> +}
> +
There's no reason to put build_slit() in the x86-specific acpi code.
It can go in hw/acpi/aml-build.c, and then we can also use it for
ARM ACPI tables too.
Thanks,
drew
