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[RFC] ich9:cpuhp: add support for cpu hot-unplug with SMI broadcast enab


From: Igor Mammedov
Subject: [RFC] ich9:cpuhp: add support for cpu hot-unplug with SMI broadcast enabled
Date: Tue, 24 Nov 2020 07:25:07 -0500

If firmware negotiates ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT feature,
OSPM on CPU eject will set bit #4 in CPU hotplug block for to be
ejected CPU to mark it for removal by firmware and trigger SMI
upcall to let firmware do actual eject.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
PS:
  - abuse 5.1 machine type for now to turn off unplug feature
    (it will be moved to 5.2 machine type once new merge window is open)
---
 include/hw/acpi/cpu.h           |  2 ++
 docs/specs/acpi_cpu_hotplug.txt | 11 +++++++++--
 hw/acpi/cpu.c                   | 18 ++++++++++++++++--
 hw/i386/acpi-build.c            |  5 +++++
 hw/i386/pc.c                    |  1 +
 hw/isa/lpc_ich9.c               |  2 +-
 6 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/include/hw/acpi/cpu.h b/include/hw/acpi/cpu.h
index 0eeedaa491..999caaf510 100644
--- a/include/hw/acpi/cpu.h
+++ b/include/hw/acpi/cpu.h
@@ -22,6 +22,7 @@ typedef struct AcpiCpuStatus {
     uint64_t arch_id;
     bool is_inserting;
     bool is_removing;
+    bool fw_remove;
     uint32_t ost_event;
     uint32_t ost_status;
 } AcpiCpuStatus;
@@ -50,6 +51,7 @@ void cpu_hotplug_hw_init(MemoryRegion *as, Object *owner,
 typedef struct CPUHotplugFeatures {
     bool acpi_1_compatible;
     bool has_legacy_cphp;
+    bool fw_unplugs_cpu;
     const char *smi_path;
 } CPUHotplugFeatures;
 
diff --git a/docs/specs/acpi_cpu_hotplug.txt b/docs/specs/acpi_cpu_hotplug.txt
index 9bb22d1270..f68ef6e06c 100644
--- a/docs/specs/acpi_cpu_hotplug.txt
+++ b/docs/specs/acpi_cpu_hotplug.txt
@@ -57,7 +57,11 @@ read access:
               It's valid only when bit 0 is set.
            2: Device remove event, used to distinguish device for which
               no device eject request to OSPM was issued.
-           3-7: reserved and should be ignored by OSPM
+           3: reserved and should be ignored by OSPM
+           4: if set to 1, OSPM requests firmware to perform device eject,
+              firmware shall clear this event by writing 1 into it before
+              performing device eject.
+           5-7: reserved and should be ignored by OSPM
     [0x5-0x7] reserved
     [0x8] Command data: (DWORD access)
           contains 0 unless value last stored in 'Command field' is one of:
@@ -82,7 +86,10 @@ write access:
                selected CPU device
             3: if set to 1 initiates device eject, set by OSPM when it
                triggers CPU device removal and calls _EJ0 method
-            4-7: reserved, OSPM must clear them before writing to register
+            4: if set to 1 OSPM hands over device eject to firmware,
+               Firmware shall issue device eject request as described above
+               (bit #3) and OSPM should not touch device eject bit (#3),
+            5-7: reserved, OSPM must clear them before writing to register
     [0x5] Command field: (1 byte access)
           value:
             0: selects a CPU device with inserting/removing events and
diff --git a/hw/acpi/cpu.c b/hw/acpi/cpu.c
index f099b50927..09d2f20dae 100644
--- a/hw/acpi/cpu.c
+++ b/hw/acpi/cpu.c
@@ -71,6 +71,7 @@ static uint64_t cpu_hotplug_rd(void *opaque, hwaddr addr, 
unsigned size)
         val |= cdev->cpu ? 1 : 0;
         val |= cdev->is_inserting ? 2 : 0;
         val |= cdev->is_removing  ? 4 : 0;
+        val |= cdev->fw_remove  ? 16 : 0;
         trace_cpuhp_acpi_read_flags(cpu_st->selector, val);
         break;
     case ACPI_CPU_CMD_DATA_OFFSET_RW:
@@ -148,6 +149,8 @@ static void cpu_hotplug_wr(void *opaque, hwaddr addr, 
uint64_t data,
             hotplug_ctrl = qdev_get_hotplug_handler(dev);
             hotplug_handler_unplug(hotplug_ctrl, dev, NULL);
             object_unparent(OBJECT(dev));
+        } else if (data & 16) {
+            cdev->fw_remove = !cdev->fw_remove;
         }
         break;
     case ACPI_CPU_CMD_OFFSET_WR:
@@ -332,6 +335,7 @@ const VMStateDescription vmstate_cpu_hotplug = {
 #define CPU_INSERT_EVENT  "CINS"
 #define CPU_REMOVE_EVENT  "CRMV"
 #define CPU_EJECT_EVENT   "CEJ0"
+#define CPU_FW_EJECT_EVENT "CEJF"
 
 void build_cpus_aml(Aml *table, MachineState *machine, CPUHotplugFeatures opts,
                     hwaddr io_base,
@@ -384,7 +388,10 @@ void build_cpus_aml(Aml *table, MachineState *machine, 
CPUHotplugFeatures opts,
         aml_append(field, aml_named_field(CPU_REMOVE_EVENT, 1));
         /* initiates device eject, write only */
         aml_append(field, aml_named_field(CPU_EJECT_EVENT, 1));
-        aml_append(field, aml_reserved_field(4));
+        aml_append(field, aml_reserved_field(1));
+        /* tell firmware to do device eject, write only */
+        aml_append(field, aml_named_field(CPU_FW_EJECT_EVENT, 1));
+        aml_append(field, aml_reserved_field(2));
         aml_append(field, aml_named_field(CPU_COMMAND, 8));
         aml_append(cpu_ctrl_dev, field);
 
@@ -419,6 +426,7 @@ void build_cpus_aml(Aml *table, MachineState *machine, 
CPUHotplugFeatures opts,
         Aml *ins_evt = aml_name("%s.%s", cphp_res_path, CPU_INSERT_EVENT);
         Aml *rm_evt = aml_name("%s.%s", cphp_res_path, CPU_REMOVE_EVENT);
         Aml *ej_evt = aml_name("%s.%s", cphp_res_path, CPU_EJECT_EVENT);
+        Aml *fw_ej_evt = aml_name("%s.%s", cphp_res_path, CPU_FW_EJECT_EVENT);
 
         aml_append(cpus_dev, aml_name_decl("_HID", aml_string("ACPI0010")));
         aml_append(cpus_dev, aml_name_decl("_CID", aml_eisaid("PNP0A05")));
@@ -461,7 +469,13 @@ void build_cpus_aml(Aml *table, MachineState *machine, 
CPUHotplugFeatures opts,
 
             aml_append(method, aml_acquire(ctrl_lock, 0xFFFF));
             aml_append(method, aml_store(idx, cpu_selector));
-            aml_append(method, aml_store(one, ej_evt));
+            if (opts.fw_unplugs_cpu) {
+                aml_append(method, aml_store(one, fw_ej_evt));
+                aml_append(method, aml_store(aml_int(OVMF_CPUHP_SMI_CMD),
+                           aml_name("%s", opts.smi_path)));
+            } else {
+                aml_append(method, aml_store(one, ej_evt));
+            }
             aml_append(method, aml_release(ctrl_lock));
         }
         aml_append(cpus_dev, method);
diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 1f5c211245..475e76f514 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -96,6 +96,7 @@ typedef struct AcpiPmInfo {
     bool s4_disabled;
     bool pcihp_bridge_en;
     bool smi_on_cpuhp;
+    bool smi_on_cpu_unplug;
     bool pcihp_root_en;
     uint8_t s4_val;
     AcpiFadtData fadt;
@@ -197,6 +198,7 @@ static void acpi_get_pm_info(MachineState *machine, 
AcpiPmInfo *pm)
     pm->pcihp_io_base = 0;
     pm->pcihp_io_len = 0;
     pm->smi_on_cpuhp = false;
+    pm->smi_on_cpu_unplug = false;
 
     assert(obj);
     init_common_fadt_data(machine, obj, &pm->fadt);
@@ -220,6 +222,8 @@ static void acpi_get_pm_info(MachineState *machine, 
AcpiPmInfo *pm)
         pm->cpu_hp_io_base = ICH9_CPU_HOTPLUG_IO_BASE;
         pm->smi_on_cpuhp =
             !!(smi_features & BIT_ULL(ICH9_LPC_SMI_F_CPU_HOTPLUG_BIT));
+        pm->smi_on_cpu_unplug =
+            !!(smi_features & BIT_ULL(ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT));
     }
 
     /* The above need not be conditional on machine type because the reset port
@@ -1582,6 +1586,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
         CPUHotplugFeatures opts = {
             .acpi_1_compatible = true, .has_legacy_cphp = true,
             .smi_path = pm->smi_on_cpuhp ? "\\_SB.PCI0.SMI0.SMIC" : NULL,
+            .fw_unplugs_cpu = pm->smi_on_cpu_unplug,
         };
         build_cpus_aml(dsdt, machine, opts, pm->cpu_hp_io_base,
                        "\\_SB.PCI0", "\\_GPE._E02");
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 17b514d1da..2952a00fe6 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -99,6 +99,7 @@
 
 GlobalProperty pc_compat_5_1[] = {
     { "ICH9-LPC", "x-smi-cpu-hotplug", "off" },
+    { "ICH9-LPC", "x-smi-cpu-hotunplug", "off" },
 };
 const size_t pc_compat_5_1_len = G_N_ELEMENTS(pc_compat_5_1);
 
diff --git a/hw/isa/lpc_ich9.c b/hw/isa/lpc_ich9.c
index 087a18d04d..8c667b7166 100644
--- a/hw/isa/lpc_ich9.c
+++ b/hw/isa/lpc_ich9.c
@@ -770,7 +770,7 @@ static Property ich9_lpc_properties[] = {
     DEFINE_PROP_BIT64("x-smi-cpu-hotplug", ICH9LPCState, smi_host_features,
                       ICH9_LPC_SMI_F_CPU_HOTPLUG_BIT, true),
     DEFINE_PROP_BIT64("x-smi-cpu-hotunplug", ICH9LPCState, smi_host_features,
-                      ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT, false),
+                      ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT, true),
     DEFINE_PROP_END_OF_LIST(),
 };
 
-- 
2.27.0




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