OpenE2K/qemu-e2k
13
4
Fork 0
Code Issues 4 Pull Requests Projects 2 Releases Activity

hw/arm/virt: Don't create device-tree node for empty NUMA node

Browse Source 
The empty NUMA node, where no memory resides, are allowed. For
example, the following command line specifies two empty NUMA nodes.
With this, QEMU fails to boot because of the conflicting device-tree
node names, as the following error message indicates.

  /home/gavin/sandbox/qemu.main/build/qemu-system-aarch64 \
  -accel kvm -machine virt,gic-version=host               \
  -cpu host -smp 4,sockets=2,cores=2,threads=1            \
  -m 1024M,slots=16,maxmem=64G                            \
  -object memory-backend-ram,id=mem0,size=512M            \
  -object memory-backend-ram,id=mem1,size=512M            \
  -numa node,nodeid=0,cpus=0-1,memdev=mem0                \
  -numa node,nodeid=1,cpus=2-3,memdev=mem1                \
  -numa node,nodeid=2                                     \
  -numa node,nodeid=3
    :
  qemu-system-aarch64: FDT: Failed to create subnode /memory@80000000: FDT_ERR_EXISTS

As specified by linux device-tree binding document, the device-tree
nodes for these empty NUMA nodes shouldn't be generated. However,
the corresponding NUMA node IDs should be included in the distance
map. The memory hotplug through device-tree on ARM64 isn't existing
so far and it's not necessary to require the user to provide a distance
map. Furthermore, the default distance map Linux generates may even be
sufficient. So this simply skips populating the device-tree nodes for
these empty NUMA nodes to avoid the error, so that QEMU can be started
successfully.

Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Message-Id: <20211015124246.23073-1-gshan@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Gavin Shan 2021-10-15 20:42:46 +08:00 committed by Richard Henderson
parent 47432863ff
commit 99abb72520
1 changed files with 13 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
hw/arm/boot.c
View File

@ -599,10 +599,23 @@ int arm_load_dtb(hwaddr addr, const struct arm_boot_info *binfo,
}
g_strfreev(node_path);
/*
* We drop all the memory nodes which correspond to empty NUMA nodes
* from the device tree, because the Linux NUMA binding document
* states they should not be generated. Linux will get the NUMA node
* IDs of the empty NUMA nodes from the distance map if they are needed.
* This means QEMU users may be obliged to provide command lines which
* configure distance maps when the empty NUMA node IDs are needed and
* Linux's default distance map isn't sufficient.
*/
if (ms->numa_state != NULL && ms->numa_state->num_nodes > 0) {
mem_base = binfo->loader_start;
for (i = 0; i < ms->numa_state->num_nodes; i++) {
mem_len = ms->numa_state->nodes[i].node_mem;
if (!mem_len) {
continue;
}
rc = fdt_add_memory_node(fdt, acells, mem_base,
scells, mem_len, i);
if (rc < 0) {