Re: [PATCH 4/8] arm: Synchronize CPU on PSCI on

[Peter Maydell]

On Thu, 26 Nov 2020 at 21:36, Alexander Graf <agraf@csgraf.de> wrote:
>
> We are going to reuse the TCG PSCI code for HVF. This however means that we
> need to ensure that CPU register state is synchronized properly between the
> two worlds.
>
> So let's make sure that at least on the PSCI on call, the secondary core gets
> to sync its registers after reset, so that changes also propagate.
>
> Signed-off-by: Alexander Graf <agraf@csgraf.de>
> ---
>  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 b75f813b40..256f7cfdcd 100644
> --- a/target/arm/arm-powerctl.c
> +++ b/target/arm/arm-powerctl.c
> @@ -15,6 +15,7 @@
>  #include "arm-powerctl.h"
>  #include "qemu/log.h"
>  #include "qemu/main-loop.h"
> +#include "sysemu/hw_accel.h"
>
>  #ifndef DEBUG_ARM_POWERCTL
>  #define DEBUG_ARM_POWERCTL 0
> @@ -66,6 +67,8 @@ static void arm_set_cpu_on_async_work(CPUState 
> *target_cpu_state,
>      cpu_reset(target_cpu_state);
>      target_cpu_state->halted = 0;
>
> +    cpu_synchronize_state(target_cpu_state);
> +
>      if (info->target_aa64) {
>          if ((info->target_el < 3) && arm_feature(&target_cpu->env,
>                                                   ARM_FEATURE_EL3))

This looks weird. The CPU was off, so not running anything.
Why doesn't the state we set up here get synchronized to
HVF as part of the normal enter-guest-code process that we
do when we do whatever HVF's equivalent of KVM_RUN is ?

Also, we change more bits of CPU state later in this function,
so if we do need to manually sychronize in this function this
doesn't seem like the right place...

thanks
-- PMM