Re: [PATCH 15/16] target/mips/cpu: Do not allow system-mode use without input clock

[Philippe Mathieu-Daudé]

On 9/29/20 3:01 PM, Igor Mammedov wrote:
> On Mon, 28 Sep 2020 19:15:38 +0200
> Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
> 
>> Now than all QOM users provides the input clock, do not allow
>> using a CPU core without its input clock connected on system-mode
>> emulation. For user-mode, keep providing a fixed 200 MHz clock,
>> as it used by the RDHWR instruction (see commit cdfcad788394).
>>
>> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
>> ---
>> Cc: Igor Mammedov <imammedo@redhat.com>
>>
>> We need the qtest check for tests/qtest/machine-none-test.c
>> which instanciate a CPU with the none machine. Igor, is it
>> better to remove the MIPS targets from the test cpus_map[]?
> 
> I don't get idea, could you rephrase/elaborate?

cpu_class_init sets:

    /*
     * Reason: CPUs still need special care by board code: wiring up
     * IRQs, adding reset handlers, halting non-first CPUs, ...
     */
    dc->user_creatable = false;

but the CPUs are created via another path in vl.c:

        current_machine->cpu_type = parse_cpu_option(cpu_option);

The machine-none-test assumes CPU objects are user-creatable.

With this patch I enforce MIPS CPU to have an input clock
connected, so they are not user-creatable anymore.

I tried this code ...:

--- a/target/mips/cpu.c
+++ b/target/mips/cpu.c
@@ -229,7 +229,11 @@ static const TypeInfo mips_cpu_type_info = {
 static void mips_cpu_cpudef_class_init(ObjectClass *oc, void *data)
 {
     MIPSCPUClass *mcc = MIPS_CPU_CLASS(oc);
+    DeviceClass *dc = DEVICE_CLASS(oc);
+
     mcc->cpu_def = data;
+    /* Reason: clock need to be wired up */
+    dc->user_creatable = false;
 }

... but it is ignored, the CPU can still be created.

Not sure how to handle this.

> 
>> ---
>>  target/mips/cpu.c | 8 ++++++++
>>  1 file changed, 8 insertions(+)
>>
>> diff --git a/target/mips/cpu.c b/target/mips/cpu.c
>> index 2f75216c324..cc4ee75af30 100644
>> --- a/target/mips/cpu.c
>> +++ b/target/mips/cpu.c
>> @@ -25,6 +25,7 @@
>>  #include "kvm_mips.h"
>>  #include "qemu/module.h"
>>  #include "sysemu/kvm.h"
>> +#include "sysemu/qtest.h"
>>  #include "exec/exec-all.h"
>>  #include "hw/qdev-clock.h"
>>  #include "hw/qdev-properties.h"
>> @@ -159,11 +160,18 @@ static void mips_cpu_realizefn(DeviceState *dev, Error 
>> **errp)
>>      Error *local_err = NULL;
>>  
>>      if (!clock_get(cs->clock)) {
>> +#ifdef CONFIG_USER_ONLY
>>          /*
>>           * Initialize the frequency to 200MHz in case
>>           * the clock remains unconnected.
>>           */
>>          clock_set_hz(cs->clock, 200000000);
>> +#else
>> +        if (!qtest_enabled()) {
>> +            error_setg(errp, "CPU clock must be connected to a clock 
>> source");
>> +            return;
>> +        }
>> +#endif
>>      }
>>      mips_cpu_clk_update(cs);
>>  
>