[Qemu-devel] [RFC PATCH 5/6] virt-acpi-build: add PPTT table

[Andrew Jones <drjones@redhat.com>]

The ACPI PPTT table supports topology descriptions for 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.

Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Shannon Zhao <zhaoshenglong@huawei.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Signed-off-by: Andrew Jones <drjones@redhat.com>
---
 hw/acpi/aml-build.c         | 50 +++++++++++++++++++++++++++++++++++++
 hw/arm/virt-acpi-build.c    |  5 ++++
 include/hw/acpi/aml-build.h |  2 ++
 3 files changed, 57 insertions(+)

diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
index 1e43cd736de9..37e8f5182ae9 100644
--- a/hw/acpi/aml-build.c
+++ b/hw/acpi/aml-build.c
@@ -24,6 +24,7 @@
 #include "hw/acpi/aml-build.h"
 #include "qemu/bswap.h"
 #include "qemu/bitops.h"
+#include "sysemu/cpus.h"
 #include "sysemu/numa.h"
 
 static GArray *build_alloc_array(void)
@@ -1679,6 +1680,55 @@ void build_slit(GArray *table_data, BIOSLinker *linker)
                  table_data->len - slit_start, 1, NULL, NULL);
 }
 
+/*
+ * ACPI 6.2 Processor Properties Topology Table (PPTT)
+ */
+static void build_cpu_hierarchy(GArray *tbl, uint32_t flags,
+                                uint32_t parent, uint32_t id)
+{
+    build_append_byte(tbl, 0);  /* Type 0 - processor */
+    build_append_byte(tbl, 20); /* Length, no private resources */
+    build_append_int_noprefix(tbl, 0, 2);           /* Reserved */
+    build_append_int_noprefix(tbl, flags, 4);
+    build_append_int_noprefix(tbl, parent, 4);
+    build_append_int_noprefix(tbl, id, 4);
+    build_append_int_noprefix(tbl, 0, 4); /* Num private resources */
+}
+
+void build_pptt(GArray *table_data, BIOSLinker *linker, int possible_cpus)
+{
+    int pptt_start = table_data->len;
+    int uid = 0, cpus = 0, socket;
+
+    acpi_data_push(table_data, sizeof(AcpiTableHeader));
+
+    for (socket = 0; cpus < possible_cpus; socket++) {
+        uint32_t socket_offset = table_data->len - pptt_start;
+        int core;
+
+        build_cpu_hierarchy(table_data, 1, 0, socket);
+
+        for (core = 0; core < smp_cores; core++) {
+            uint32_t core_offset = table_data->len - pptt_start;
+            int thread;
+
+            if (smp_threads > 1) {
+                build_cpu_hierarchy(table_data, 0, socket_offset, core);
+                for (thread = 0; thread < smp_threads; thread++) {
+                    build_cpu_hierarchy(table_data, 2, core_offset, uid++);
+                }
+             } else {
+                build_cpu_hierarchy(table_data, 2, socket_offset, uid++);
+             }
+        }
+        cpus += smp_cores * smp_threads;
+    }
+
+    build_header(linker, table_data,
+                 (void *)(table_data->data + pptt_start), "PPTT",
+                 table_data->len - pptt_start, 1, NULL, NULL);
+}
+
 /* build rev1/rev3/rev5.1 FADT */
 void build_fadt(GArray *tbl, BIOSLinker *linker, const AcpiFadtData *f,
                 const char *oem_id, const char *oem_table_id)
diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
index 1d1fc824da6f..aa77e1f018d9 100644
--- a/hw/arm/virt-acpi-build.c
+++ b/hw/arm/virt-acpi-build.c
@@ -832,6 +832,11 @@ void virt_acpi_build(VirtMachineState *vms, AcpiBuildTables *tables)
     acpi_add_table(table_offsets, tables_blob);
     build_madt(tables_blob, tables->linker, vms);
 
+    if (!vmc->ignore_cpu_topology) {
+        acpi_add_table(table_offsets, tables_blob);
+        build_pptt(tables_blob, tables->linker, possible_cpus(vms));
+    }
+
     acpi_add_table(table_offsets, tables_blob);
     build_gtdt(tables_blob, tables->linker, vms);
 
diff --git a/include/hw/acpi/aml-build.h b/include/hw/acpi/aml-build.h
index 6c36903c0a5d..2b0fde6bd417 100644
--- a/include/hw/acpi/aml-build.h
+++ b/include/hw/acpi/aml-build.h
@@ -414,6 +414,8 @@ void build_srat_memory(AcpiSratMemoryAffinity *numamem, uint64_t base,
 
 void build_slit(GArray *table_data, BIOSLinker *linker);
 
+void build_pptt(GArray *table_data, BIOSLinker *linker, int possible_cpus);
+
 void build_fadt(GArray *tbl, BIOSLinker *linker, const AcpiFadtData *f,
                 const char *oem_id, const char *oem_table_id);
 #endif
-- 
2.17.1