[Qemu-devel] [RFC PATCH 6/7] cpu hotplug: implement function cpu_status_write() for vcpu ejection

[Gu Zheng]

From: Chen Fan <address@hidden>

When OS ejected a vcpu (like: echo 1 > /sys/bus/acpi/devices/LNXCPUXX/eject),
it would call acpi EJ0 method, the firmware need to write the new cpumap, QEMU
would know which vcpu need to be ejected.

TODO:
-confirm the hotplug result via OST if guest support it.

Signed-off-by: Chen Fan <address@hidden>
Signed-off-by: Gu Zheng <address@hidden>
---
 cpus.c                            |    7 ++++++
 hw/acpi/cpu_hotplug.c             |   40 ++++++++++++++++++++++++++++++++++++-
 hw/i386/acpi-dsdt-cpu-hotplug.dsl |    6 ++++-
 include/hw/acpi/cpu_hotplug.h     |    1 +
 include/qom/cpu.h                 |    9 ++++++++
 5 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/cpus.c b/cpus.c
index 5e7f2cf..4dfb889 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1117,6 +1117,13 @@ void resume_all_vcpus(void)
     }
 }
 
+void cpu_remove(CPUState *cpu)
+{
+    cpu->stop = true;
+    cpu->exit = true;
+    qemu_cpu_kick(cpu);
+}
+
 /* For temporary buffers for forming a name */
 #define VCPU_THREAD_NAME_SIZE 16
 
diff --git a/hw/acpi/cpu_hotplug.c b/hw/acpi/cpu_hotplug.c
index 56cb316..7cbce69 100644
--- a/hw/acpi/cpu_hotplug.c
+++ b/hw/acpi/cpu_hotplug.c
@@ -20,10 +20,46 @@ static uint64_t cpu_status_read(void *opaque, hwaddr addr, 
unsigned int size)
     return val;
 }
 
+static void acpi_eject_vcpu(AcpiCpuHotplug *cpus_status, int64_t cpu_id)
+{
+    CPUState *cpu;
+
+    CPU_FOREACH(cpu) {
+        CPUClass *cc = CPU_GET_CLASS(cpu);
+        int64_t id = cc->get_arch_id(cpu);
+
+        if (cpu_id == id) {
+            cpus_status->old_sts[cpu_id / 8] &= ~(1 << (cpu_id % 8));
+            cpus_status->sts[cpu_id / 8] &= ~(1 << (cpu_id % 8));
+            cpu_remove(cpu);
+            break;
+        }
+    }
+}
+
 static void cpu_status_write(void *opaque, hwaddr addr, uint64_t data,
                              unsigned int size)
 {
-    /* TODO: implement VCPU removal on guest signal that CPU can be removed */
+    AcpiCpuHotplug *cpus = opaque;
+    uint8_t val;
+    int i;
+    int64_t cpu_id = -1;
+
+    val = cpus->old_sts[addr] ^ data;
+
+    if (val == 0) {
+        return;
+    }
+
+    for (i = 0; i < 8; i++) {
+        if (val & 1 << i) {
+            cpu_id = 8 * addr + i;
+        }
+    }
+
+    if (cpu_id != -1) {
+        acpi_eject_vcpu(cpus, cpu_id);
+    }
 }
 
 static const MemoryRegionOps AcpiCpuHotplug_ops = {
@@ -49,6 +85,7 @@ void AcpiCpuHotplug_handle(ACPIGPE *gpe, AcpiCpuHotplug *g,
 
     if (type == PLUG) {
         g->sts[cpu_id / 8] |= (1 << (cpu_id % 8));
+        g->old_sts[cpu_id / 8] |= (1 << (cpu_id % 8));
     } else {
         g->sts[cpu_id / 8] &= ~(1 << (cpu_id % 8));
     }
@@ -65,6 +102,7 @@ void AcpiCpuHotplug_init(MemoryRegion *parent, Object *owner,
 
         g_assert((id / 8) < ACPI_GPE_PROC_LEN);
         gpe_cpu->sts[id / 8] |= (1 << (id % 8));
+        gpe_cpu->old_sts[id / 8] |= (1 << (id % 8));
     }
     memory_region_init_io(&gpe_cpu->io, owner, &AcpiCpuHotplug_ops,
                           gpe_cpu, "acpi-cpu-hotplug", ACPI_GPE_PROC_LEN);
diff --git a/hw/i386/acpi-dsdt-cpu-hotplug.dsl 
b/hw/i386/acpi-dsdt-cpu-hotplug.dsl
index 34aab5a..9485f12 100644
--- a/hw/i386/acpi-dsdt-cpu-hotplug.dsl
+++ b/hw/i386/acpi-dsdt-cpu-hotplug.dsl
@@ -50,7 +50,11 @@ Scope(\_SB) {
     }
     Method(CPEJ, 2, NotSerialized) {
         // _EJ0 method - eject callback
-        Sleep(200)
+        Store(Zero, Index(CPON, ToInteger(Arg0)))
+        Store(One, Local0)
+        ShiftLeft(Local0, Arg0, Local0)
+        Not(Local0, Local0)
+        And(PRS, Local0, PRS)
     }
 
 #define CPU_STATUS_LEN ACPI_GPE_PROC_LEN
diff --git a/include/hw/acpi/cpu_hotplug.h b/include/hw/acpi/cpu_hotplug.h
index 4fe0066..3bffc69 100644
--- a/include/hw/acpi/cpu_hotplug.h
+++ b/include/hw/acpi/cpu_hotplug.h
@@ -28,6 +28,7 @@ typedef struct CPUNotifier {
 typedef struct AcpiCpuHotplug {
     MemoryRegion io;
     uint8_t sts[ACPI_GPE_PROC_LEN];
+    uint8_t old_sts[ACPI_GPE_PROC_LEN];
 } AcpiCpuHotplug;
 
 void AcpiCpuHotplug_handle(ACPIGPE *gpe, AcpiCpuHotplug *g,
diff --git a/include/qom/cpu.h b/include/qom/cpu.h
index 2fc00ef..9108dc6 100644
--- a/include/qom/cpu.h
+++ b/include/qom/cpu.h
@@ -236,6 +236,7 @@ struct CPUState {
     bool created;
     bool stop;
     bool stopped;
+    bool exit;
     volatile sig_atomic_t exit_request;
     uint32_t interrupt_request;
     int singlestep_enabled;
@@ -600,6 +601,14 @@ void cpu_exit(CPUState *cpu);
 void cpu_resume(CPUState *cpu);
 
 /**
+ * cpu_remove:
+ * @cpu: The vCPU to remove.
+ *
+ * Requests the CPU @cpu to be removed.
+ */
+void cpu_remove(CPUState *cpu);
+
+/**
  * qemu_init_vcpu:
  * @cpu: The vCPU to initialize.
  *
-- 
1.7.7