@@ -551,6 +551,18 @@ int e820_add_entry(uint64_t address, uint64_t length, uint32_t type)
return index;
}
+/* Calculates the limit to CPU APIC ID values
+ *
+ * This function returns the limit for the APIC ID value, so that all
+ * CPU APIC IDs are < pc_apic_id_limit().
+ *
+ * This is used for FW_CFG_MAX_CPUS. See comments on bochs_bios_init().
+ */
+static unsigned int pc_apic_id_limit(unsigned int max_cpus)
+{
+ return x86_cpu_apic_id_from_index(max_cpus - 1) + 1;
+}
+
static void *bochs_bios_init(void)
{
void *fw_cfg;
@@ -558,9 +570,24 @@ static void *bochs_bios_init(void)
size_t smbios_len;
uint64_t *numa_fw_cfg;
int i, j;
+ unsigned int apic_id_limit = pc_apic_id_limit(max_cpus);
fw_cfg = fw_cfg_init(BIOS_CFG_IOPORT, BIOS_CFG_IOPORT + 1, 0, 0);
- fw_cfg_add_i16(fw_cfg, FW_CFG_MAX_CPUS, (uint16_t)max_cpus);
+ /* FW_CFG_MAX_CPUS is a bit confusing/problematic on x86:
+ *
+ * SeaBIOS needs FW_CFG_MAX_CPUS for CPU hotplug, but the CPU hotplug
+ * QEMU<->SeaBIOS interface is not based on the "CPU index", but on the APIC
+ * ID of hotplugged CPUs[1]. This means that FW_CFG_MAX_CPUS is not the
+ * "maximum number of CPUs", but the "limit to the APIC ID values SeaBIOS
+ * may see".
+ *
+ * So, this means we must not use max_cpus, here, but the maximum possible
+ * APIC ID value, plus one.
+ *
+ * [1] The only kind of "CPU identifier" used between SeaBIOS and QEMU is
+ * the APIC ID, not the "CPU index"
+ */
+ fw_cfg_add_i16(fw_cfg, FW_CFG_MAX_CPUS, (uint16_t)apic_id_limit);
fw_cfg_add_i32(fw_cfg, FW_CFG_ID, 1);
fw_cfg_add_i64(fw_cfg, FW_CFG_RAM_SIZE, (uint64_t)ram_size);
fw_cfg_add_bytes(fw_cfg, FW_CFG_ACPI_TABLES,
@@ -579,21 +606,24 @@ static void *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 + max_cpus + nb_numa_nodes);
+ numa_fw_cfg = g_new0(uint64_t, 1 + apic_id_limit + nb_numa_nodes);
numa_fw_cfg[0] = cpu_to_le64(nb_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++) {
if (test_bit(i, node_cpumask[j])) {
- numa_fw_cfg[i + 1] = cpu_to_le64(j);
+ numa_fw_cfg[apic_id + 1] = cpu_to_le64(j);
break;
}
}
}
for (i = 0; i < nb_numa_nodes; i++) {
- numa_fw_cfg[max_cpus + 1 + i] = cpu_to_le64(node_mem[i]);
+ numa_fw_cfg[apic_id_limit + 1 + i] = cpu_to_le64(node_mem[i]);
}
fw_cfg_add_bytes(fw_cfg, FW_CFG_NUMA, numa_fw_cfg,
- (1 + max_cpus + nb_numa_nodes) * sizeof(*numa_fw_cfg));
+ (1 + apic_id_limit + nb_numa_nodes) *
+ sizeof(*numa_fw_cfg));
return fw_cfg;
}
This changes FW_CFG_MAX_CPUS and FW_CFG_NUMA to use apic_id_for_cpu(), so the NUMA table can be based on the APIC IDs, instead of CPU index (SeaBIOS knows nothing about CPU indexes, just APIC IDs). Signed-off-by: Eduardo Habkost <ehabkost@redhat.com> --- Changes v2: - Get PC object as argument - Add more detailed comments explaining the reason for FW_CFG_MAX_CPUS not being simply 'max_cpus' Changes v3: - Use PCInitArgs instead of PC object Changes v4: - Don't use PCInitArgs, just add the necessary data for apic_id_limit() as argument - Rename function to pc_apic_id_limit() - Rename max_apic_id to apic_id_limit Changes v5: - Refresh after apic_id_for_cpu() -> x86_cpu_apic_id_from_index() rename - Refresh after original code changes to use g_new0() Changes v6: - Eliminate cpu_idx variable (use 'i', 'j', instead) Suggested-by: Andreas Färber <afaerber@suse.de> --- hw/pc.c | 40 +++++++++++++++++++++++++++++++++++----- 1 file changed, 35 insertions(+), 5 deletions(-)