[5/7] ppc: force update of all msr bits in cpu_post_load

Since env->msr has already been restored by the time cpu_post_load is called,
make sure that ppc_store_msr() is explicitly called with all msr bits marked
as invalid.

This solves the issue where MSR flags aren't set correctly when restoring a VM
snapshot, in particular the internal env->excp_prefix value when MSR_EP has
been altered by a guest.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
---
 target-ppc/machine.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

On 23/12/2014 01:36, Mark Cave-Ayland wrote:
> Since env->msr has already been restored by the time cpu_post_load is called,
> make sure that ppc_store_msr() is explicitly called with all msr bits marked
> as invalid.
> 
> This solves the issue where MSR flags aren't set correctly when restoring a VM
> snapshot, in particular the internal env->excp_prefix value when MSR_EP has
> been altered by a guest.
> 
> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> ---
>  target-ppc/machine.c |    8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/target-ppc/machine.c b/target-ppc/machine.c
> index c801b82..9669063 100644
> --- a/target-ppc/machine.c
> +++ b/target-ppc/machine.c
> @@ -159,6 +159,7 @@ static int cpu_post_load(void *opaque, int version_id)
>      PowerPCCPU *cpu = opaque;
>      CPUPPCState *env = &cpu->env;
>      int i;
> +    target_ulong msr;
>  
>      /*
>       * We always ignore the source PVR. The user or management
> @@ -190,7 +191,12 @@ static int cpu_post_load(void *opaque, int version_id)
>          /* Restore htab_base and htab_mask variables */
>          ppc_store_sdr1(env, env->spr[SPR_SDR1]);
>      }
> -    hreg_compute_hflags(env);
> +
> +    /* Mark all msr bits invalid before restoring */
> +    msr = env->msr;
> +    env->msr = ~env->msr;
> +    ppc_store_msr(env, msr);
> +
>      hreg_compute_mem_idx(env);
>  
>      return 0;
> 

This is wrong for this line of hreg_store_msr:

    if (unlikely((env->flags & POWERPC_FLAG_TGPR) &&
                 ((value ^ env->msr) & (1 << MSR_TGPR)))) {
        /* Swap temporary saved registers with GPRs */
        hreg_swap_gpr_tgpr(env);
    }

I think you need to change the ~ with "^ ~(1 << MSR_TGPR)".

Paolo

On 20/01/15 15:01, Paolo Bonzini wrote:

> On 23/12/2014 01:36, Mark Cave-Ayland wrote:
>> Since env->msr has already been restored by the time cpu_post_load is called,
>> make sure that ppc_store_msr() is explicitly called with all msr bits marked
>> as invalid.
>>
>> This solves the issue where MSR flags aren't set correctly when restoring a VM
>> snapshot, in particular the internal env->excp_prefix value when MSR_EP has
>> been altered by a guest.
>>
>> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
>> ---
>>  target-ppc/machine.c |    8 +++++++-
>>  1 file changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/target-ppc/machine.c b/target-ppc/machine.c
>> index c801b82..9669063 100644
>> --- a/target-ppc/machine.c
>> +++ b/target-ppc/machine.c
>> @@ -159,6 +159,7 @@ static int cpu_post_load(void *opaque, int version_id)
>>      PowerPCCPU *cpu = opaque;
>>      CPUPPCState *env = &cpu->env;
>>      int i;
>> +    target_ulong msr;
>>  
>>      /*
>>       * We always ignore the source PVR. The user or management
>> @@ -190,7 +191,12 @@ static int cpu_post_load(void *opaque, int version_id)
>>          /* Restore htab_base and htab_mask variables */
>>          ppc_store_sdr1(env, env->spr[SPR_SDR1]);
>>      }
>> -    hreg_compute_hflags(env);
>> +
>> +    /* Mark all msr bits invalid before restoring */
>> +    msr = env->msr;
>> +    env->msr = ~env->msr;
>> +    ppc_store_msr(env, msr);
>> +
>>      hreg_compute_mem_idx(env);
>>  
>>      return 0;
>>
> 
> This is wrong for this line of hreg_store_msr:
> 
>     if (unlikely((env->flags & POWERPC_FLAG_TGPR) &&
>                  ((value ^ env->msr) & (1 << MSR_TGPR)))) {
>         /* Swap temporary saved registers with GPRs */
>         hreg_swap_gpr_tgpr(env);
>     }
> 
> I think you need to change the ~ with "^ ~(1 << MSR_TGPR)".

It took me a little time to decipher how that worked, but yes it seems
fine in my tests here. I'll resend the series with with your Reviewed-by
added to the previous patch.


Many thanks,

Mark.