Re: [PATCH qemu] spapr: Force 32bit when resetting a core

[Cédric Le Goater]

On 1/7/22 08:24, Alexey Kardashevskiy wrote:
> "PowerPC Processor binding to IEEE 1275" says in
> "8.2.1. Initial Register Values" that the initial state is defined as
> 32bit so do it for both SLOF and VOF.
>
> This should not cause behavioral change as SLOF switches to 64bit very
> early anyway. As nothing enforces LE anywhere, this drops it for VOF.
>
> The goal is to make VOF work with TCG as otherwise it barfs with
> qemu: fatal: TCG hflags mismatch (current:0x6c000004 rebuilt:0x6c000000)
>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
>   hw/ppc/spapr_cpu_core.c | 5 +++++
>   hw/ppc/spapr_vof.c      | 2 --
>   2 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
> index a57ba70a8781..a781e97f8d1d 100644
> --- a/hw/ppc/spapr_cpu_core.c
> +++ b/hw/ppc/spapr_cpu_core.c
> @@ -37,6 +37,11 @@ static void spapr_reset_vcpu(PowerPCCPU *cpu)
>   
>       cpu_reset(cs);
>   
> +    /*
> +     * "PowerPC Processor binding to IEEE 1275" defines the initial MSR state
> +     * as 32bit (MSR_SF=0) in "8.2.1. Initial Register Values".
> +     */

Indeed but this seems to contradict 8b9f2118ca40 ("ppc64: set MSR_SF bit").

Laurent, would you remember the reason for forcing 64bit ? It's been a while
since.

Thanks,

C.


> +    env->msr &= ~(1ULL << MSR_SF);
>       env->spr[SPR_HIOR] = 0;
>   
>       lpcr = env->spr[SPR_LPCR];
> diff --git a/hw/ppc/spapr_vof.c b/hw/ppc/spapr_vof.c
> index 40ce8fe0037c..a33f940c32bb 100644
> --- a/hw/ppc/spapr_vof.c
> +++ b/hw/ppc/spapr_vof.c
> @@ -88,8 +88,6 @@ void spapr_vof_reset(SpaprMachineState *spapr, void *fdt, 
> Error **errp)
>       spapr_cpu_set_entry_state(first_ppc_cpu, SPAPR_ENTRY_POINT,
>                                 stack_ptr, spapr->initrd_base,
>                                 spapr->initrd_size);
> -    /* VOF is 32bit BE so enforce MSR here */
> -    first_ppc_cpu->env.msr &= ~((1ULL << MSR_SF) | (1ULL << MSR_LE));
>   
>       /*
>        * At this point the expected allocation map is: