[RFC PATCH v2 5/6] hw/arm/virt-acpi-build: Add PPTT table

[Yanan Wang]

Add the Processor Properties Topology Table (PPTT) to present
CPU topology information to ACPI guests. Note, while a DT boot
Linux guest with a non-flat CPU topology will see socket and
core IDs being sequential integers starting from zero, e.g.
with -smp 4,sockets=2,cores=2,threads=1

a DT boot produces

 cpu:  0 package_id:  0 core_id:  0
 cpu:  1 package_id:  0 core_id:  1
 cpu:  2 package_id:  1 core_id:  0
 cpu:  3 package_id:  1 core_id:  1

an ACPI boot produces

 cpu:  0 package_id: 36 core_id:  0
 cpu:  1 package_id: 36 core_id:  1
 cpu:  2 package_id: 96 core_id:  2
 cpu:  3 package_id: 96 core_id:  3

This is due to several reasons:

 1) DT cpu nodes do not have an equivalent field to what the PPTT
    ACPI Processor ID must be, i.e. something equal to the MADT CPU
    UID or equal to the UID of an ACPI processor container. In both
    ACPI cases those are platform dependant IDs assigned by the
    vendor.

 2) While QEMU is the vendor for a guest, if the topology specifies
    SMT (> 1 thread), then, with ACPI, it is impossible to assign a
    core-id the same value as a package-id, thus it is not possible
    to have package-id=0 and core-id=0. This is because package and
    core containers must be in the same ACPI namespace and therefore
    must have unique UIDs.

 3) ACPI processor containers are not required for PPTT tables to
    be used and, due to the limitations of which IDs are selected
    described above in (2), they are not helpful for QEMU, so we
    don't build them with this patch. In the absence of them, Linux
    assigns its own unique IDs. The maintainers have chosen not to use
    counters from zero, but rather ACPI table offsets, which explains
    why the numbers are so much larger than with DT.

 4) When there is no SMT (threads=1) the core IDs for ACPI boot guests
    match the logical CPU IDs, because these IDs must be equal to the
    MADT CPU UID (as no processor containers are present), and QEMU
    uses the logical CPU ID for these MADT IDs.

Tested-by: Jiajie Li <lijiajie11@huawei.com>
Signed-off-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Ying Fang <fangying1@huawei.com>
Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
---
 hw/arm/virt-acpi-build.c | 63 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)

diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
index 2ad5dad1bf..03fd812d5a 100644
--- a/hw/arm/virt-acpi-build.c
+++ b/hw/arm/virt-acpi-build.c
@@ -436,6 +436,64 @@ build_srat(GArray *table_data, BIOSLinker *linker, 
VirtMachineState *vms)
                  vms->oem_table_id);
 }
 
+/* PPTT */
+static void
+build_pptt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
+{
+    int pptt_start = table_data->len;
+    int uid = 0, cpus = 0, socket = 0;
+    MachineState *ms = MACHINE(vms);
+    unsigned int smp_cores = ms->smp.cores;
+    unsigned int smp_threads = ms->smp.threads;
+
+    acpi_data_push(table_data, sizeof(AcpiTableHeader));
+
+    for (socket = 0; cpus < ms->possible_cpus->len; socket++) {
+        uint32_t socket_offset = table_data->len - pptt_start;
+        int core;
+
+        build_processor_hierarchy_node(
+            table_data, 1, /* Physical package */
+            0, socket, /* No parent */
+            NULL, 0);  /* No private resources */
+
+        for (core = 0; core < smp_cores; core++) {
+            uint32_t core_offset = table_data->len - pptt_start;
+            int thread;
+
+            if (smp_threads <= 1) {
+                build_processor_hierarchy_node(
+                    table_data,
+                    (1 << 1) | /* ACPI Processor ID valid */
+                    (1 << 3),  /* ACPI 6.3 - Node is a Leaf */
+                    socket_offset, uid++, /* Parent is a Socket */
+                    NULL, 0);  /* No private resources */
+            } else {
+                build_processor_hierarchy_node(
+                    table_data, 0,
+                    socket_offset, core, /* Parent is a Socket */
+                    NULL, 0); /* No private resources */
+
+                for (thread = 0; thread < smp_threads; thread++) {
+                    build_processor_hierarchy_node(
+                        table_data,
+                        (1 << 1) | /* ACPI Processor ID valid */
+                        (1 << 2) | /* ACPI 6.3 - Processor is a Thread */
+                        (1 << 3),  /* ACPI 6.3 - Node is a Leaf */
+                        core_offset, uid++, /* Parent is a Core */
+                        NULL, 0);  /* No private resources */
+                }
+            }
+        }
+        cpus += smp_cores * smp_threads;
+    }
+
+    build_header(linker, table_data,
+                 (void *)(table_data->data + pptt_start), "PPTT",
+                 table_data->len - pptt_start, 2,
+                 vms->oem_id, vms->oem_table_id);
+}
+
 /* GTDT */
 static void
 build_gtdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
@@ -707,6 +765,11 @@ void virt_acpi_build(VirtMachineState *vms, 
AcpiBuildTables *tables)
     acpi_add_table(table_offsets, tables_blob);
     build_madt(tables_blob, tables->linker, vms);
 
+    if (ms->smp.cpus > 1 && !vmc->no_cpu_topology) {
+        acpi_add_table(table_offsets, tables_blob);
+        build_pptt(tables_blob, tables->linker, vms);
+    }
+
     acpi_add_table(table_offsets, tables_blob);
     build_gtdt(tables_blob, tables->linker, vms);
 
-- 
2.19.1