[Qemu-devel] [RFC PATCH v4] numa: enable sparse node numbering on ppc

[Nishanth Aravamudan]

Sparse node numbering occurs on powerpc in practice under PowerVM. In
order to emulate the same NUMA topology under qemu, the assumption that
NUMA nodes are linearly ordered has to be removed. qemu was recently
modified to reject requests for sparse NUMA node numbering.

Leverage the present field in NodeInfo which indicates if a given nodeid
was present on the command-line or not. Adjust the iteration of various
NUMA loops to use the maximum known NUMA ID rather than the number of
NUMA nodes.

numa.c::set_numa_nodes() has become a bit more convoluted for
round-robin'ing the CPUs over known nodes when not specified by the
user.

Note that the x86 code needs changes for both sparse node numbering and
memoryless nodes, and the ppc code needs changes for memoryless nodes.
ppc also requires node 0 to be present on the command-line (or else it
fails with: "qemu: pSeries SLOF firmware requires >= 128M guest RMA
(Real Mode Area memory)". Alexey has a series to address the latter.

Examples:

Before:
    mlock=off -numa node,nodeid=3 -numa node,nodeid=0 -smp 4
qemu-system-ppc64-base: numa: Node ID missing: 2

After:
(qemu) info numa
2 nodes
node 0 cpus: 1 3
node 0 size: 2048 MB
node 3 cpus: 0 2
node 3 size: 2048 MB

available: 2 nodes (0,3)
node 0 cpus: 1 3
node 0 size: 2030 MB
node 0 free: 1934 MB
node 3 cpus: 0 2
node 3 size: 2045 MB
node 3 free: 1957 MB
node distances:
node   0   3
  0:  10  40
  3:  40  10

Signed-off-by: Nishanth Aravamudan <address@hidden>
    
---
I understand that 2.1 is in freeze, so I'm not requesting this be
applied, but would like feedback to have this ready to queue up for the
next release.

v1 -> v2:
  Modify set_numa_nodes loop for round-robin'ing CPUs.

v2 -> v3:
  Updated changelog to indicate problem being solved.
  Updated memory_region_allocate_system_memory based upon feedback from
    Hu.
  Updated set_numa_nodes loop again to be simpler based upon feedback
    from Hu.
  Fixed bug with a mix of nodes with nodeid specified and without, where
    the same nodeid would be used by the explicit specification and the
    auto-numbering code.

v3 -> v4:
  Rename nb_numa_nodes to num_numa_nodes to help catch usage.
  Rebased to master/origin as Eduardo's patches to support the Present
    flag have gone upstream.
  Disable sparse node numbering on i386, enable it on ppc.

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 2cf22b1..cdefafe 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -698,23 +698,23 @@ static FWCfgState *bochs_bios_init(void)
      * of nodes, one word for each VCPU->node and one word for each node to
      * hold the amount of memory.
      */
-    numa_fw_cfg = g_new0(uint64_t, 1 + apic_id_limit + nb_numa_nodes);
-    numa_fw_cfg[0] = cpu_to_le64(nb_numa_nodes);
+    numa_fw_cfg = g_new0(uint64_t, 1 + apic_id_limit + num_numa_nodes);
+    numa_fw_cfg[0] = cpu_to_le64(num_numa_nodes);
     for (i = 0; i < max_cpus; i++) {
         unsigned int apic_id = x86_cpu_apic_id_from_index(i);
         assert(apic_id < apic_id_limit);
-        for (j = 0; j < nb_numa_nodes; j++) {
+        for (j = 0; j < num_numa_nodes; j++) {
             if (test_bit(i, numa_info[j].node_cpu)) {
                 numa_fw_cfg[apic_id + 1] = cpu_to_le64(j);
                 break;
             }
         }
     }
-    for (i = 0; i < nb_numa_nodes; i++) {
+    for (i = 0; i < num_numa_nodes; i++) {
         numa_fw_cfg[apic_id_limit + 1 + i] = 
cpu_to_le64(numa_info[i].node_mem);
     }
     fw_cfg_add_bytes(fw_cfg, FW_CFG_NUMA, numa_fw_cfg,
-                     (1 + apic_id_limit + nb_numa_nodes) *
+                     (1 + apic_id_limit + num_numa_nodes) *
                      sizeof(*numa_fw_cfg));
 
     return fw_cfg;
@@ -1121,10 +1121,22 @@ PcGuestInfo *pc_guest_info_init(ram_addr_t 
below_4g_mem_size,
     guest_info->ram_size = below_4g_mem_size + above_4g_mem_size;
     guest_info->apic_id_limit = pc_apic_id_limit(max_cpus);
     guest_info->apic_xrupt_override = kvm_allows_irq0_override();
-    guest_info->numa_nodes = nb_numa_nodes;
+    /* No support for sparse NUMA node IDs yet: */
+    for (i = max_numa_nodeid - 1; i >= 0; i--) {
+        /* Report large node IDs first, to make mistakes easier to spot */
+        if (!numa_info[i].present) {
+            error_report("numa: Node ID missing: %d", i);
+            exit(EXIT_FAILURE);
+        }
+    }
+
+    /* This must be always true if all nodes are present */
+    assert(num_numa_nodes == max_numa_nodeid);
+
+    guest_info->numa_nodes = num_numa_nodes;
     guest_info->node_mem = g_malloc0(guest_info->numa_nodes *
                                     sizeof *guest_info->node_mem);
-    for (i = 0; i < nb_numa_nodes; i++) {
+    for (i = 0; i < num_numa_nodes; i++) {
         guest_info->node_mem[i] = numa_info[i].node_mem;
     }
 
@@ -1134,7 +1146,7 @@ PcGuestInfo *pc_guest_info_init(ram_addr_t 
below_4g_mem_size,
     for (i = 0; i < max_cpus; i++) {
         unsigned int apic_id = x86_cpu_apic_id_from_index(i);
         assert(apic_id < guest_info->apic_id_limit);
-        for (j = 0; j < nb_numa_nodes; j++) {
+        for (j = 0; j < num_numa_nodes; j++) {
             if (test_bit(i, numa_info[j].node_cpu)) {
                 guest_info->node_cpu[apic_id] = j;
                 break;
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index a8ba916..9a247f8 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -226,7 +226,7 @@ static int spapr_fixup_cpu_dt(void *fdt, sPAPREnvironment 
*spapr)
             }
         }
 
-        if (nb_numa_nodes > 1) {
+        if (num_numa_nodes > 1) {
             ret = fdt_setprop(fdt, offset, "ibm,associativity", associativity,
                               sizeof(associativity));
             if (ret < 0) {
@@ -608,7 +608,7 @@ static int spapr_populate_memory(sPAPREnvironment *spapr, 
void *fdt)
     int i, off;
 
     /* memory node(s) */
-    if (nb_numa_nodes > 1 && numa_info[0].node_mem < ram_size) {
+    if (num_numa_nodes > 1 && numa_info[0].node_mem < ram_size) {
         node0_size = numa_info[0].node_mem;
     } else {
         node0_size = ram_size;
@@ -642,7 +642,10 @@ static int spapr_populate_memory(sPAPREnvironment *spapr, 
void *fdt)
 
     /* RAM: Node 1 and beyond */
     mem_start = node0_size;
-    for (i = 1; i < nb_numa_nodes; i++) {
+    for (i = 1; i < max_numa_nodeid; i++) {
+        if (!numa_info[i].present) {
+            continue;
+        }
         mem_reg_property[0] = cpu_to_be64(mem_start);
         if (mem_start >= ram_size) {
             node_size = 0;
@@ -792,7 +795,7 @@ static void spapr_reset_htab(sPAPREnvironment *spapr)
 
     /* Update the RMA size if necessary */
     if (spapr->vrma_adjust) {
-        hwaddr node0_size = (nb_numa_nodes > 1) ?
+        hwaddr node0_size = (num_numa_nodes > 1) ?
             numa_info[0].node_mem : ram_size;
         spapr->rma_size = kvmppc_rma_size(node0_size, spapr->htab_shift);
     }
@@ -1225,7 +1228,7 @@ static void ppc_spapr_init(MachineState *machine)
     MemoryRegion *sysmem = get_system_memory();
     MemoryRegion *ram = g_new(MemoryRegion, 1);
     hwaddr rma_alloc_size;
-    hwaddr node0_size = (nb_numa_nodes > 1) ? numa_info[0].node_mem : ram_size;
+    hwaddr node0_size = (num_numa_nodes > 1) ? numa_info[0].node_mem : 
ram_size;
     uint32_t initrd_base = 0;
     long kernel_size = 0, initrd_size = 0;
     long load_limit, rtas_limit, fw_size;
diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index d8539fd..d17bdbe 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -146,7 +146,7 @@ extern int mem_prealloc;
  */
 #define MAX_CPUMASK_BITS 255
 
-extern int nb_numa_nodes;   /* Number of NUMA nodes */
+extern int num_numa_nodes;  /* Number of NUMA nodes */
 extern int max_numa_nodeid; /* Highest specified NUMA node ID, plus one.
                              * For all nodes, nodeid < max_numa_nodeid
                              */
diff --git a/monitor.c b/monitor.c
index 5bc70a6..53955e4 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1948,8 +1948,11 @@ static void do_info_numa(Monitor *mon, const QDict 
*qdict)
     int i;
     CPUState *cpu;
 
-    monitor_printf(mon, "%d nodes\n", nb_numa_nodes);
-    for (i = 0; i < nb_numa_nodes; i++) {
+    monitor_printf(mon, "%d nodes\n", num_numa_nodes);
+    for (i = 0; i < max_numa_nodeid; i++) {
+        if (!numa_info[i].present) {
+            continue;
+        }
         monitor_printf(mon, "node %d cpus:", i);
         CPU_FOREACH(cpu) {
             if (cpu->numa_node == i) {
diff --git a/numa.c b/numa.c
index 2fde740..42ebe85 100644
--- a/numa.c
+++ b/numa.c
@@ -53,7 +53,10 @@ static void numa_node_parse(NumaNodeOptions *node, QemuOpts 
*opts, Error **errp)
     if (node->has_nodeid) {
         nodenr = node->nodeid;
     } else {
-        nodenr = nb_numa_nodes;
+        nodenr = 0;
+        while (numa_info[nodenr].present) {
+            nodenr++;
+        }
     }
 
     if (nodenr >= MAX_NODES) {
@@ -136,7 +139,7 @@ int numa_init_func(QemuOpts *opts, void *opaque)
         if (err) {
             goto error;
         }
-        nb_numa_nodes++;
+        num_numa_nodes++;
         break;
     default:
         abort();
@@ -160,53 +163,44 @@ error:
 
 void set_numa_nodes(void)
 {
-    int i;
+    int i, j;
 
     assert(max_numa_nodeid <= MAX_NODES);
 
-    /* No support for sparse NUMA node IDs yet: */
-    for (i = max_numa_nodeid - 1; i >= 0; i--) {
-        /* Report large node IDs first, to make mistakes easier to spot */
-        if (!numa_info[i].present) {
-            error_report("numa: Node ID missing: %d", i);
-            exit(1);
-        }
-    }
-
-    /* This must be always true if all nodes are present: */
-    assert(nb_numa_nodes == max_numa_nodeid);
-
-    if (nb_numa_nodes > 0) {
+    if (num_numa_nodes > 0) {
         uint64_t numa_total;
 
-        if (nb_numa_nodes > MAX_NODES) {
-            nb_numa_nodes = MAX_NODES;
+        if (num_numa_nodes > MAX_NODES) {
+            num_numa_nodes = MAX_NODES;
         }
 
         /* If no memory size is given for any node, assume the default case
          * and distribute the available memory equally across all nodes
          */
-        for (i = 0; i < nb_numa_nodes; i++) {
-            if (numa_info[i].node_mem != 0) {
+        for (i = 0; i < max_numa_nodeid; i++) {
+            if (numa_info[i].present && numa_info[i].node_mem != 0) {
                 break;
             }
         }
-        if (i == nb_numa_nodes) {
+        if (i == max_numa_nodeid) {
             uint64_t usedmem = 0;
 
             /* On Linux, each node's border has to be 8MB aligned,
              * the final node gets the rest.
              */
-            for (i = 0; i < nb_numa_nodes - 1; i++) {
-                numa_info[i].node_mem = (ram_size / nb_numa_nodes) &
-                                        ~((1 << 23UL) - 1);
-                usedmem += numa_info[i].node_mem;
+            for (i = 0; i < max_numa_nodeid - 1; i++) {
+                if (numa_info[i].present) {
+                    numa_info[i].node_mem = (ram_size / num_numa_nodes) &
+                                            ~((1 << 23UL) - 1);
+                    usedmem += numa_info[i].node_mem;
+                }
             }
+           assert(numa_info[i].present);
             numa_info[i].node_mem = ram_size - usedmem;
         }
 
         numa_total = 0;
-        for (i = 0; i < nb_numa_nodes; i++) {
+        for (i = 0; i < max_numa_nodeid; i++) {
             numa_total += numa_info[i].node_mem;
         }
         if (numa_total != ram_size) {
@@ -216,8 +210,9 @@ void set_numa_nodes(void)
             exit(1);
         }
 
-        for (i = 0; i < nb_numa_nodes; i++) {
-            if (!bitmap_empty(numa_info[i].node_cpu, MAX_CPUMASK_BITS)) {
+        for (i = 0; i < max_numa_nodeid; i++) {
+            if (numa_info[i].present &&
+                !bitmap_empty(numa_info[i].node_cpu, MAX_CPUMASK_BITS)) {
                 break;
             }
         }
@@ -225,9 +220,12 @@ void set_numa_nodes(void)
          * must cope with this anyway, because there are BIOSes out there in
          * real machines which also use this scheme.
          */
-        if (i == nb_numa_nodes) {
-            for (i = 0; i < max_cpus; i++) {
-                set_bit(i, numa_info[i % nb_numa_nodes].node_cpu);
+        if (i == max_numa_nodeid) {
+            for (i = 0, j = 0; i < max_cpus; i++) {
+               do {
+                    j = (j + 1) % (max_numa_nodeid);
+               } while (!numa_info[j].present);
+                set_bit(i, numa_info[j].node_cpu);
             }
         }
     }
@@ -239,8 +237,9 @@ void set_numa_modes(void)
     int i;
 
     CPU_FOREACH(cpu) {
-        for (i = 0; i < nb_numa_nodes; i++) {
-            if (test_bit(cpu->cpu_index, numa_info[i].node_cpu)) {
+        for (i = 0; i < max_numa_nodeid; i++) {
+            if (numa_info[i].present &&
+                test_bit(cpu->cpu_index, numa_info[i].node_cpu)) {
                 cpu->numa_node = i;
             }
         }
@@ -282,16 +281,19 @@ void memory_region_allocate_system_memory(MemoryRegion 
*mr, Object *owner,
     uint64_t addr = 0;
     int i;
 
-    if (nb_numa_nodes == 0 || !have_memdevs) {
+    if (num_numa_nodes == 0 || !have_memdevs) {
         allocate_system_memory_nonnuma(mr, owner, name, ram_size);
         return;
     }
 
     memory_region_init(mr, owner, name, ram_size);
-    for (i = 0; i < MAX_NODES; i++) {
+    for (i = 0; i < max_numa_nodeid; i++) {
         Error *local_err = NULL;
         uint64_t size = numa_info[i].node_mem;
         HostMemoryBackend *backend = numa_info[i].node_memdev;
+        if (!numa_info[i].present) {
+            continue;
+        }
         if (!backend) {
             continue;
         }
diff --git a/vl.c b/vl.c
index 41ddcd2..5da4cc2 100644
--- a/vl.c
+++ b/vl.c
@@ -195,7 +195,7 @@ struct FWBootEntry {
 static QTAILQ_HEAD(, FWBootEntry) fw_boot_order =
     QTAILQ_HEAD_INITIALIZER(fw_boot_order);
 
-int nb_numa_nodes;
+int num_numa_nodes;
 int max_numa_nodeid;
 NodeInfo numa_info[MAX_NODES];
 
@@ -2989,7 +2989,7 @@ int main(int argc, char **argv, char **envp)
         bitmap_zero(numa_info[i].node_cpu, MAX_CPUMASK_BITS);
     }
 
-    nb_numa_nodes = 0;
+    num_numa_nodes = 0;
     max_numa_nodeid = 0;
     nb_nics = 0;