Re: [PATCH v3 14/16] hw/ppc: Use hreg_store_msr for msr updates

[Richard Henderson]

On 3/15/21 4:23 AM, Cédric Le Goater wrote:
> On 3/14/21 6:59 PM, Richard Henderson wrote:
> > Only one of the three places in hw/ppc that modify msr updated
> > hflags.  Even in that case, use the official interface instead
> > of a direct call to hreg_compute_hflags.
>
> ppc_store_msr() is the interface to use.
>
> > Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> > ---
> > Cc: Cédric Le Goater <clg@kaod.org>
> > Cc: Greg Kurz <groug@kaod.org>
> > ---
> >   hw/ppc/pnv_core.c    | 3 ++-
> >   hw/ppc/spapr_hcall.c | 3 +--
> >   hw/ppc/spapr_rtas.c  | 3 ++-
> >   3 files changed, 5 insertions(+), 4 deletions(-)
> >
> > diff --git a/hw/ppc/pnv_core.c b/hw/ppc/pnv_core.c
> > index bd2bf2e044..31f041b9c7 100644
> > --- a/hw/ppc/pnv_core.c
> > +++ b/hw/ppc/pnv_core.c
> > @@ -29,6 +29,7 @@
> >   #include "hw/ppc/pnv_xscom.h"
> >   #include "hw/ppc/xics.h"
> >   #include "hw/qdev-properties.h"
> > +#include "helper_regs.h"
> >   
> >   static const char *pnv_core_cpu_typename(PnvCore *pc)
> >   {
> > @@ -54,7 +55,7 @@ static void pnv_core_cpu_reset(PnvCore *pc, PowerPCCPU *cpu)
> >        */
> >       env->gpr[3] = PNV_FDT_ADDR;
> >       env->nip = 0x10;
> > -    env->msr |= MSR_HVB; /* Hypervisor mode */
> > +    hreg_store_msr(env, env->msr | MSR_HVB, true); /* Hypervisor mode */
>
>
> This is going to have the opposite effect of not setting the HV bit in the
> PowerNV machine. See the comment in powerpc_set_excp_state().
>
> May be commit 1c953ba57ada ("ppc: Fix hreg_store_msr() so that non-HV
> mode cannot alter MSR:HV") needs a fix first.

Hmm.  I mis-read the code and assumed "allow_hv" allowed hv to be changed. 
There must be some kind of quirkyness here that I don't understand.

I'll just have these reset functions use hreg_recompute_hflags directly.


r~