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

[Igor Mammedov]

On Tue, 29 Sep 2020 16:40:24 +0200
Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:

> 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[]?
it will help to pass test but,

> > 
> > 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.

user_creatable -> able to create using -device, 
so test doesn't make this assumption.

problem is that enforcing would make machine-none not usable
for probing CPU features which is used by mgmt,
so that would break.

> 
> 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);
> >>    
> >   
>