Re: [Qemu-devel] [PATCH 05/17] ppc: Fix hreg_store_msr() so that non-HV mode cannot alter MSR:HV

[David Gibson]

On Mon, Mar 14, 2016 at 08:29:10PM +0100, Thomas Huth wrote:
> On 14.03.2016 17:56, Cédric Le Goater wrote:
> > From: Benjamin Herrenschmidt 
> > 
> > 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 
> > Reviewed-by: David Gibson 
> > ---
> >  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 c890853d861b..37d4721db63b 100644
> > --- a/target-ppc/excp_helper.c
> > +++ b/target-ppc/excp_helper.c
> > @@ -666,8 +666,12 @@ 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 271fddf17f0a..844240d1a755 100644
> > --- a/target-ppc/helper_regs.h
> > +++ b/target-ppc/helper_regs.h
> > @@ -75,8 +75,8 @@ 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;
> >  }
> 
> Reviewed-by: Thomas Huth 

This looks correct, but I'm not seeing a strong case for including it
before 2.6.

-- 
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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Re: [Qemu-devel] [PATCH 05/17] ppc: Fix hreg_store_msr() so that non-HV mode cannot alter MSR:HV

[Thomas Huth]

On 14.03.2016 17:56, Cédric Le Goater wrote:
> From: Benjamin Herrenschmidt 
> 
> 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 
> Reviewed-by: David Gibson 
> ---
>  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 c890853d861b..37d4721db63b 100644
> --- a/target-ppc/excp_helper.c
> +++ b/target-ppc/excp_helper.c
> @@ -666,8 +666,12 @@ 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 271fddf17f0a..844240d1a755 100644
> --- a/target-ppc/helper_regs.h
> +++ b/target-ppc/helper_regs.h
> @@ -75,8 +75,8 @@ 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;
>  }

Reviewed-by: Thomas Huth 

[Qemu-devel] [PATCH 05/17] ppc: Fix hreg_store_msr() so that non-HV mode cannot alter MSR:HV

[Cédric Le Goater]

From: Benjamin Herrenschmidt 

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 
Reviewed-by: David Gibson 
---
 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 c890853d861b..37d4721db63b 100644
--- a/target-ppc/excp_helper.c
+++ b/target-ppc/excp_helper.c
@@ -666,8 +666,12 @@ 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 271fddf17f0a..844240d1a755 100644
--- a/target-ppc/helper_regs.h
+++ b/target-ppc/helper_regs.h
@@ -75,8 +75,8 @@ 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;
 }
-- 
2.1.4