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Re: [PATCH v6 06/18] spapr, ppc: Remove VPM0/RMLS hacks for POWER9


From: Greg Kurz
Subject: Re: [PATCH v6 06/18] spapr, ppc: Remove VPM0/RMLS hacks for POWER9
Date: Tue, 25 Feb 2020 12:29:00 +0100

On Tue, 25 Feb 2020 10:37:12 +1100
David Gibson <address@hidden> wrote:

> For the "pseries" machine, we use "virtual hypervisor" mode where we
> only model the CPU in non-hypervisor privileged mode.  This means that
> we need guest physical addresses within the modelled cpu to be treated
> as absolute physical addresses.
> 
> We used to do that by clearing LPCR[VPM0] and setting LPCR[RMLS] to a high
> limit so that the old offset based translation for guest mode applied,
> which does what we need.  However, POWER9 has removed support for that
> translation mode, which meant we had some ugly hacks to keep it working.
> 
> We now explicitly handle this sort of translation for virtual hypervisor
> mode, so the hacks aren't necessary.  We don't need to set VPM0 and RMLS
> from the machine type code - they're now ignored in vhyp mode.  On the cpu
> side we don't need to allow LPCR[RMLS] to be set on POWER9 in vhyp mode -
> that was only there to allow the hack on the machine side.
> 
> Signed-off-by: David Gibson <address@hidden>
> Reviewed-by: C├ędric Le Goater <address@hidden>
> ---

Reviewed-by: Greg Kurz <address@hidden>

>  hw/ppc/spapr_cpu_core.c | 6 +-----
>  target/ppc/mmu-hash64.c | 8 --------
>  2 files changed, 1 insertion(+), 13 deletions(-)
> 
> diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
> index d09125d9af..ea5e11f1d9 100644
> --- a/hw/ppc/spapr_cpu_core.c
> +++ b/hw/ppc/spapr_cpu_core.c
> @@ -58,14 +58,10 @@ static void spapr_reset_vcpu(PowerPCCPU *cpu)
>       * we don't get spurious wakups before an RTAS start-cpu call.
>       * For the same reason, set PSSCR_EC.
>       */
> -    lpcr &= ~(LPCR_VPM0 | LPCR_VPM1 | LPCR_ISL | LPCR_KBV | pcc->lpcr_pm);
> +    lpcr &= ~(LPCR_VPM1 | LPCR_ISL | LPCR_KBV | pcc->lpcr_pm);
>      lpcr |= LPCR_LPES0 | LPCR_LPES1;
>      env->spr[SPR_PSSCR] |= PSSCR_EC;
>  
> -    /* Set RMLS to the max (ie, 16G) */
> -    lpcr &= ~LPCR_RMLS;
> -    lpcr |= 1ull << LPCR_RMLS_SHIFT;
> -
>      ppc_store_lpcr(cpu, lpcr);
>  
>      /* Set a full AMOR so guest can use the AMR as it sees fit */
> diff --git a/target/ppc/mmu-hash64.c b/target/ppc/mmu-hash64.c
> index e372c42add..caf47ad6fc 100644
> --- a/target/ppc/mmu-hash64.c
> +++ b/target/ppc/mmu-hash64.c
> @@ -1126,14 +1126,6 @@ void ppc_store_lpcr(PowerPCCPU *cpu, target_ulong val)
>                        (LPCR_PECE_L_MASK & (LPCR_PDEE | LPCR_HDEE | LPCR_EEE |
>                        LPCR_DEE | LPCR_OEE)) | LPCR_MER | LPCR_GTSE | LPCR_TC 
> |
>                        LPCR_HEIC | LPCR_LPES0 | LPCR_HVICE | LPCR_HDICE);
> -        /*
> -         * If we have a virtual hypervisor, we need to bring back RMLS. It
> -         * doesn't exist on an actual P9 but that's all we know how to
> -         * configure with softmmu at the moment
> -         */
> -        if (cpu->vhyp) {
> -            lpcr |= (val & LPCR_RMLS);
> -        }
>          break;
>      default:
>          g_assert_not_reached();




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