Re: [Qemu-devel] [PATCH 2/4] spapr: introduce a helper to compute the address of the HPT

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

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On Mon, Sep 04, 2017 at 11:47:05PM +0200, Greg Kurz wrote:
> The formula used to compute the address of the HPT allocated by QEMU is
> open-coded in several places. This patch moves the magic to a dedicated
> helper. While here, we also patch the callers to only pass the address
> to KVM if we indeed have a userland HPT (ie, KVM PR).

The helper function seems reasonable, though I'm not sure about the
name (a. it's not just a pointer, since it includes the encoded size
and b. the name doesn't indicate this is basically KVM PR specific).

THe "only pass the address to KVM if we indeed have a userland HPT
(ie, KVM PR)" bit doesn't really work.  You're doing it by testing for
(sdr1 != 0), but that can only be true if the HPT is minimum size,
which doesn't have much to do with anything meaningful.

> Signed-off-by: Greg Kurz <groug@kaod.org>
> ---
>  hw/ppc/spapr.c          |    9 +++++++++
>  hw/ppc/spapr_cpu_core.c |   12 +++++++-----
>  hw/ppc/spapr_hcall.c    |   14 ++++++++------
>  include/hw/ppc/spapr.h  |    1 +
>  4 files changed, 25 insertions(+), 11 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index caffa1276328..bf24c26b756d 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1290,6 +1290,15 @@ static void spapr_store_hpte(PPCVirtualHypervisor *vhyp, hwaddr ptex,
>      }
>  }
>  
> +target_ulong spapr_get_hpt_pointer(sPAPRMachineState *spapr)
> +{
> +    if (!spapr->htab) {
> +        return 0;
> +    }
> +
> +    return (target_ulong)(uintptr_t)spapr->htab | (spapr->htab_shift - 18);
> +}
> +
>  int spapr_hpt_shift_for_ramsize(uint64_t ramsize)
>  {
>      int shift;
> diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
> index 85037ef71e27..581eb4d92de9 100644
> --- a/hw/ppc/spapr_cpu_core.c
> +++ b/hw/ppc/spapr_cpu_core.c
> @@ -93,11 +93,13 @@ static void spapr_cpu_reset(void *opaque)
>       * HPT
>       */
>      if (kvm_enabled()) {
> -        env->spr[SPR_SDR1] = (target_ulong)(uintptr_t)spapr->htab
> -            | (spapr->htab_shift - 18);
> -        if (kvmppc_put_books_sregs(cpu) < 0) {
> -            error_report("Unable to update SDR1 in KVM");
> -            exit(1);
> +        target_ulong sdr1 = spapr_get_hpt_pointer(spapr);
> +        if (sdr1) {
> +            env->spr[SPR_SDR1] = sdr1;
> +            if (kvmppc_put_books_sregs(cpu) < 0) {
> +                error_report("Unable to update SDR1 in KVM");
> +                exit(1);
> +            }
>          }
>      }
>  }
> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> index 6ab8c188f381..06059b44ab40 100644
> --- a/hw/ppc/spapr_hcall.c
> +++ b/hw/ppc/spapr_hcall.c
> @@ -735,9 +735,10 @@ static target_ulong h_resize_hpt_commit(PowerPCCPU *cpu,
>  
>          if (kvm_enabled()) {
>              /* For KVM PR, update the HPT pointer */
> -            target_ulong sdr1 = (target_ulong)(uintptr_t)spapr->htab
> -                | (spapr->htab_shift - 18);
> -            kvmppc_update_sdr1(sdr1);
> +            target_ulong sdr1 = spapr_get_hpt_pointer(spapr);
> +            if (sdr1) {
> +                kvmppc_update_sdr1(sdr1);
> +            }
>          }
>  
>          pending->hpt = NULL; /* so it's not free()d */
> @@ -1566,9 +1567,10 @@ static target_ulong h_client_architecture_support(PowerPCCPU *cpu,
>              spapr_reallocate_hpt(spapr, maxshift, &error_fatal);
>              if (kvm_enabled()) {
>                  /* For KVM PR, update the HPT pointer */
> -                target_ulong sdr1 = (target_ulong)(uintptr_t)spapr->htab
> -                    | (spapr->htab_shift - 18);
> -                kvmppc_update_sdr1(sdr1);
> +                target_ulong sdr1 = spapr_get_hpt_pointer(spapr);
> +                if (sdr1) {
> +                    kvmppc_update_sdr1(sdr1);
> +                }
>              }
>          }
>      }
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index c1b365f56431..a1f5edc15018 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -709,4 +709,5 @@ void spapr_do_system_reset_on_cpu(CPUState *cs, run_on_cpu_data arg);
>  int spapr_vcpu_id(PowerPCCPU *cpu);
>  PowerPCCPU *spapr_find_cpu(int vcpu_id);
>  
> +target_ulong spapr_get_hpt_pointer(sPAPRMachineState *spapr);
>  #endif /* HW_SPAPR_H */
> 

-- 
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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