diff options
| -rw-r--r-- | hw/pc.c | 40 |
1 files changed, 35 insertions, 5 deletions
@@ -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; } |