On Wed, Nov 11, 2015 at 11:27:23AM +1100, Benjamin Herrenschmidt wrote: > This helper is only used by the various instructions that can alter > MSR and not interrupts. Add a comment to that effect to the interrupt > code as well in case somebody wants to change this > > Signed-off-by: Benjamin Herrenschmidt <b...@kernel.crashing.org>
Reviewed-by: David Gibson <da...@gibson.dropbear.id.au>
> ---
> target-ppc/excp_helper.c | 8 ++++++--
> target-ppc/helper_regs.h | 4 ++--
> 2 files changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/target-ppc/excp_helper.c b/target-ppc/excp_helper.c
> index 00fae60..83e6c07 100644
> --- a/target-ppc/excp_helper.c
> +++ b/target-ppc/excp_helper.c
> @@ -662,8 +662,12 @@ static inline void powerpc_excp(PowerPCCPU *cpu, int
> excp_model, int excp)
> }
> }
> #endif
> - /* XXX: we don't use hreg_store_msr here as already have treated
> - * any special case that could occur. Just store MSR and update
> hflags
> + /* We don't use hreg_store_msr here as already have treated
> + * any special case that could occur. Just store MSR and update hflags
> + *
> + * Note: We *MUST* not use hreg_store_msr() as-is anyway because it
> + * will prevent setting of the HV bit which some exceptions might need
> + * to do.
> */
> env->msr = new_msr & env->msr_mask;
> hreg_compute_hflags(env);
> diff --git a/target-ppc/helper_regs.h b/target-ppc/helper_regs.h
> index 57da931..12af61c 100644
> --- a/target-ppc/helper_regs.h
> +++ b/target-ppc/helper_regs.h
> @@ -114,8 +114,8 @@ static inline int hreg_store_msr(CPUPPCState *env,
> target_ulong value,
> excp = 0;
> value &= env->msr_mask;
> #if !defined(CONFIG_USER_ONLY)
> - if (!alter_hv) {
> - /* mtmsr cannot alter the hypervisor state */
> + /* Neither mtmsr nor guest state can alter HV */
> + if (!alter_hv || !(env->msr & MSR_HVB)) {
> value &= ~MSR_HVB;
> value |= env->msr & MSR_HVB;
> }
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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