Re: [Qemu-devel] [Qemu-ppc] [PATCH 07/12] ppc: Better figure out if processor has HV mode

[David Gibson <david@gibson.dropbear.id.au>]

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On Fri, May 27, 2016 at 09:56:32AM +0200, Cédric Le Goater wrote:
> On 05/27/2016 05:38 AM, David Gibson wrote:
> > On Tue, May 03, 2016 at 06:03:29PM +0200, Cédric Le Goater wrote:
> >> From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> >>
> >> We use an env. flag which is set to the initial value of MSR_HVB in
> >> the msr_mask. We also adjust the POWER8 mask to set SHV.
> >>
> >> Also use this to adjust ctx.hv so that it is *set* when the processor
> >> doesn't have an HV mode (970 with Apple mode for example), thus enabling
> >> hypervisor instructions/SPRs.
> >>
> >> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> >> Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
> >> ---
> >>  target-ppc/cpu.h            |  4 ++++
> >>  target-ppc/translate.c      |  4 +++-
> >>  target-ppc/translate_init.c | 21 ++++++++++++++++-----
> >>  3 files changed, 23 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/target-ppc/cpu.h b/target-ppc/cpu.h
> >> index 2a96efcbf813..02f2e72e6d14 100644
> >> --- a/target-ppc/cpu.h
> >> +++ b/target-ppc/cpu.h
> >> @@ -1161,6 +1161,10 @@ struct CPUPPCState {
> >>      hwaddr mpic_iack;
> >>      /* true when the external proxy facility mode is enabled */
> >>      bool mpic_proxy;
> >> +    /* set when the processor has an HV mode, thus HV priv
> >> +     * instructions and SPRs are diallowed if MSR:HV is 0
> >> +     */
> >> +    bool has_hv_mode;
> >>  #endif
> >>  
> >>      /* Those resources are used only during code translation */
> >> diff --git a/target-ppc/translate.c b/target-ppc/translate.c
> >> index 7a672cba796d..6f55bcd34a74 100644
> >> --- a/target-ppc/translate.c
> >> +++ b/target-ppc/translate.c
> >> @@ -11495,8 +11495,10 @@ void gen_intermediate_code(CPUPPCState *env, struct TranslationBlock *tb)
> >>      ctx.exception = POWERPC_EXCP_NONE;
> >>      ctx.spr_cb = env->spr_cb;
> >>      ctx.pr = msr_pr;
> >> -    ctx.hv = !msr_pr && msr_hv;
> > 
> > The test for msr_pr has been removed in the new version.  Maybe that's
> > safe, but I think it needs some justification.
> 
> I don't know if it is safe to run with (MSR_HV|MSR_PR) = 11

Um.. I believe host userland runs routinely in that state.

> There is a note in the Power ISA book describing such a case but I am not 
> sure qemu-ppc supports that. So I will keep the msr_pr check in the next 
> version :
> 
> 	ctx.hv = !msr_pr && (msr_hv || !env->has_hv_mode);

Ok.

-- 
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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