[Qemu-devel] [RFC][PATCH 1/6] piix4: implement function 'cpu_status_write' for vcpu ejection

[Chen Fan]

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

Signed-off-by: Chen Fan <address@hidden>
---
 hw/acpi/piix4.c | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/hw/acpi/piix4.c b/hw/acpi/piix4.c
index c885690..1aaa7a4 100644
--- a/hw/acpi/piix4.c
+++ b/hw/acpi/piix4.c
@@ -61,6 +61,7 @@ struct pci_status {
 
 typedef struct CPUStatus {
     uint8_t sts[PIIX4_PROC_LEN];
+    uint8_t old_sts[PIIX4_PROC_LEN];
 } CPUStatus;
 
 typedef struct PIIX4PMState {
@@ -610,6 +611,12 @@ static const MemoryRegionOps piix4_pci_ops = {
     },
 };
 
+static void acpi_piix_eject_vcpu(int64_t cpuid)
+{
+    /* TODO: eject a vcpu, release allocated vcpu and exit the vcpu pthread.  
*/
+    PIIX4_DPRINTF("vcpu: %" PRIu64 " need to be ejected.\n", cpuid);
+}
+
 static uint64_t cpu_status_read(void *opaque, hwaddr addr, unsigned int size)
 {
     PIIX4PMState *s = opaque;
@@ -622,7 +629,26 @@ static uint64_t cpu_status_read(void *opaque, hwaddr addr, 
unsigned int size)
 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 */
+    PIIX4PMState *s = opaque;
+    CPUStatus *cpus = &s->gpe_cpu;
+    uint8_t val;
+    int i;
+    int64_t cpuid = 0;
+
+    val = cpus->old_sts[addr] ^ data;
+
+    if (val == 0)
+        return;
+
+    for (i = 0; i < 8; i++) {
+        if (val & 1 << i) {
+            cpuid = 8 * addr + i;
+        }
+    }
+
+    if (cpuid != 0) {
+        acpi_piix_eject_vcpu(cpuid);
+    }
 }
 
 static const MemoryRegionOps cpu_hotplug_ops = {
@@ -647,11 +673,17 @@ static void piix4_cpu_hotplug_req(PIIX4PMState *s, 
CPUState *cpu,
     ACPIGPE *gpe = &s->ar.gpe;
     CPUClass *k = CPU_GET_CLASS(cpu);
     int64_t cpu_id;
+    int i;
 
     assert(s != NULL);
 
     *gpe->sts = *gpe->sts | PIIX4_CPU_HOTPLUG_STATUS;
     cpu_id = k->get_arch_id(CPU(cpu));
+
+    for (i = 0; i < PIIX4_PROC_LEN; i++) {
+        g->old_sts[i] = g->sts[i];
+    }
+
     if (action == PLUG) {
         g->sts[cpu_id / 8] |= (1 << (cpu_id % 8));
     } else {
@@ -675,6 +707,7 @@ static void piix4_init_cpu_status(CPUState *cpu, void *data)
 
     g_assert((id / 8) < PIIX4_PROC_LEN);
     g->sts[id / 8] |= (1 << (id % 8));
+    g->old_sts[id / 8] |= (1 << (id % 8));
 }
 
 static int piix4_device_hotplug(DeviceState *qdev, PCIDevice *dev,
-- 
1.8.1.4