hw/i386/vmport: Add support for CMD_GETHZ

This command returns to guest information on LAPIC bus frequency and TSC
frequency.

One can see how this interface is used by Linux vmware_platform_setup()
introduced in Linux commit 88b094fb8d4f ("x86: Hypervisor detection and
get tsc_freq from hypervisor").
Reviewed-by: NNikita Leshenko <nikita.leshchenko@oracle.com>
Signed-off-by: NLiran Alon <liran.alon@oracle.com>
Message-Id: <20200312165431.82118-16-liran.alon@oracle.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/i386/vmport.c

@@ -174,6 +174,24 @@ static uint32_t vmport_cmd_ram_size(void *opaque, uint32_t addr)
     return ram_size;
 }
 
+static uint32_t vmport_cmd_get_hz(void *opaque, uint32_t addr)
+{
+    X86CPU *cpu = X86_CPU(current_cpu);
+
+    if (cpu->env.tsc_khz && cpu->env.apic_bus_freq) {
+        uint64_t tsc_freq = (uint64_t)cpu->env.tsc_khz * 1000;
+
+        cpu->env.regs[R_ECX] = cpu->env.apic_bus_freq;
+        cpu->env.regs[R_EBX] = (uint32_t)(tsc_freq >> 32);
+        cpu->env.regs[R_EAX] = (uint32_t)tsc_freq;
+    } else {
+        /* Signal cmd as not supported */
+        cpu->env.regs[R_EBX] = UINT32_MAX;
+    }
+
+    return cpu->env.regs[R_EAX];
+}
+
 static uint32_t vmport_cmd_get_vcpu_info(void *opaque, uint32_t addr)
 {
     X86CPU *cpu = X86_CPU(current_cpu);
@@ -211,6 +229,7 @@ static void vmport_realizefn(DeviceState *dev, Error **errp)
     vmport_register(VMPORT_CMD_GETRAMSIZE, vmport_cmd_ram_size, NULL);
     if (s->compat_flags & VMPORT_COMPAT_CMDS_V2) {
         vmport_register(VMPORT_CMD_GETBIOSUUID, vmport_cmd_get_bios_uuid, NULL);
+        vmport_register(VMPORT_CMD_GETHZ, vmport_cmd_get_hz, NULL);
         vmport_register(VMPORT_CMD_GET_VCPU_INFO, vmport_cmd_get_vcpu_info,
                         NULL);
     }

include/hw/i386/vmport.h

@@ -13,6 +13,7 @@ typedef enum {
     VMPORT_CMD_VMMOUSE_DATA     = 39,
     VMPORT_CMD_VMMOUSE_STATUS   = 40,
     VMPORT_CMD_VMMOUSE_COMMAND  = 41,
+    VMPORT_CMD_GETHZ            = 45,
     VMPORT_CMD_GET_VCPU_INFO    = 68,
     VMPORT_ENTRIES
 } VMPortCommand;