Re: [PATCH v2 06/10] arm/arm-powerctl: rebuild hflags after setting CP15 bits in arm_set_cpu_on()

[Peter Maydell]

Cc'ing Richard : this is one for you I think... (surely we
need to rebuild the hflags from scratch when we power up
a CPU anyway?)

thanks
-- PMM

On Mon, 16 Dec 2019 at 23:44, Niek Linnenbank <address@hidden> wrote:
>
> Hello Peter,
>
> In the previous version of this patch series I included the fix for setting 
> CP10,CP11 bits
> in arm_set_cpu_on(), which is now in master (0c7f8c43daf65560). While that 
> worked, I did not
> realize that setting those bits require rebuilding the flags. Philippe 
> reported this [1] initially,
> later on during review we discussed [2] and attempted to correct it [3].
>
> Could you please have a short look at this? Right now I don't see anymore
> issues, but I'm just not very familiar with this area of the code.
>
> Regards,
> Niek
>
> [1] https://lists.gnu.org/archive/html/qemu-devel/2019-12/msg01920.html
> [2] https://lists.gnu.org/archive/html/qemu-devel/2019-12/msg02784.html
> [3] https://lists.gnu.org/archive/html/qemu-devel/2019-12/msg02785.html
>
>
> On Tue, Dec 17, 2019 at 12:36 AM Niek Linnenbank <address@hidden> wrote:
>>
>> After setting CP15 bits in arm_set_cpu_on() the cached hflags must
>> be rebuild to reflect the changed processor state. Without rebuilding,
>> the cached hflags would be inconsistent until the next call to
>> arm_rebuild_hflags(). When QEMU is compiled with debugging enabled
>> (--enable-debug), this problem is captured shortly after the first
>> call to arm_set_cpu_on() for CPUs running in ARM 32-bit non-secure mode:
>>
>>   qemu-system-arm: target/arm/helper.c:11359: cpu_get_tb_cpu_state:
>>   Assertion `flags == rebuild_hflags_internal(env)' failed.
>>   Aborted (core dumped)
>>
>> Fixes: 0c7f8c43daf65
>> Signed-off-by: Niek Linnenbank <address@hidden>
>> ---
>>  target/arm/arm-powerctl.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/target/arm/arm-powerctl.c b/target/arm/arm-powerctl.c
>> index b064513d44..b75f813b40 100644
>> --- a/target/arm/arm-powerctl.c
>> +++ b/target/arm/arm-powerctl.c
>> @@ -127,6 +127,9 @@ static void arm_set_cpu_on_async_work(CPUState 
>> *target_cpu_state,
>>          target_cpu->env.regs[0] = info->context_id;
>>      }
>>
>> +    /* CP15 update requires rebuilding hflags */
>> +    arm_rebuild_hflags(&target_cpu->env);
>> +
>>      /* Start the new CPU at the requested address */
>>      cpu_set_pc(target_cpu_state, info->entry);
>>
>> --
>> 2.17.1
>>
>
>
> --
> Niek Linnenbank