Re: [Qemu-ppc] [PATCH v4 3/8] spapr: Only setup HPT if necessary

[David Gibson]

On Thu, Mar 16, 2017 at 05:08:15PM +1100, Sam Bobroff wrote:
> If QEMU is using KVM, and KVM is capable of running in radix mode,
> guests can be run in real-mode without allocating a HPT (because KVM
> will use a minimal RPT). So in this case, we avoid creating the HPT
> at reset time and later (during CAS) create it if it is necessary.
> 
> Signed-off-by: Sam Bobroff <address@hidden>

Reviewed-by: David Gibson <address@hidden>

> ---
> Changes in v4:
> * Fixed typo in title.
> * Reworked to track that no HPT has been allocated using the GR bit of PATB.
> 
>  hw/ppc/spapr.c         | 30 +++++++++++++++++++-----------
>  hw/ppc/spapr_hcall.c   |  7 +++++++
>  include/hw/ppc/spapr.h |  1 +
>  3 files changed, 27 insertions(+), 11 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index d96e5f60fe..f264773e11 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1239,6 +1239,17 @@ static void spapr_reallocate_hpt(sPAPRMachineState 
> *spapr, int shift,
>      }
>  }
>  
> +void spapr_setup_hpt_and_vrma(sPAPRMachineState *spapr)
> +{
> +    spapr_reallocate_hpt(spapr,
> +                     
> spapr_hpt_shift_for_ramsize(MACHINE(spapr)->maxram_size),
> +                     &error_fatal);
> +    if (spapr->vrma_adjust) {
> +        spapr->rma_size = kvmppc_rma_size(spapr_node0_size(),
> +                                          spapr->htab_shift);
> +    }
> +}
> +
>  static void find_unknown_sysbus_device(SysBusDevice *sbdev, void *opaque)
>  {
>      bool matched = false;
> @@ -1267,17 +1278,14 @@ static void ppc_spapr_reset(void)
>      /* Check for unknown sysbus devices */
>      foreach_dynamic_sysbus_device(find_unknown_sysbus_device, NULL);
>  
> -    spapr->patb_entry = 0;
> -
> -    /* Allocate and/or reset the hash page table */
> -    spapr_reallocate_hpt(spapr,
> -                         spapr_hpt_shift_for_ramsize(machine->maxram_size),
> -                         &error_fatal);
> -
> -    /* Update the RMA size if necessary */
> -    if (spapr->vrma_adjust) {
> -        spapr->rma_size = kvmppc_rma_size(spapr_node0_size(),
> -                                          spapr->htab_shift);
> +    if (kvm_enabled() && kvmppc_has_cap_mmu_radix()) {
> +        /* If using KVM with radix mode available, VCPUs can be started
> +         * without a HPT because KVM will start them in radix mode.
> +         * Set the GR bit in PATB so that we know there is no HPT. */
> +        spapr->patb_entry = PATBE1_GR;
> +    } else {
> +        spapr->patb_entry = 0;
> +        spapr_setup_hpt_and_vrma(spapr);
>      }
>  
>      qemu_devices_reset();
> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> index f05a90ed2c..1ce21af9f4 100644
> --- a/hw/ppc/spapr_hcall.c
> +++ b/hw/ppc/spapr_hcall.c
> @@ -999,6 +999,13 @@ static target_ulong 
> h_client_architecture_support(PowerPCCPU *cpu,
>      ov5_updates = spapr_ovec_new();
>      spapr->cas_reboot = spapr_ovec_diff(ov5_updates,
>                                          ov5_cas_old, spapr->ov5_cas);
> +    /* If the HPT hasn't yet been set up (see
> +     * ppc_spapr_reset()), but it's now needed, do it now: */
> +    if ((spapr->patb_entry & PATBE1_GR) &&
> +        !spapr_ovec_test(ov5_updates, OV5_MMU_RADIX)) {
> +        /* legacy hash or new hash: */
> +        spapr_setup_hpt_and_vrma(spapr);
> +    }
>  
>      if (!spapr->cas_reboot) {
>          spapr->cas_reboot =
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index ba9e689ee2..8aeb7f5758 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -605,6 +605,7 @@ void spapr_dt_events(sPAPRMachineState *sm, void *fdt);
>  int spapr_h_cas_compose_response(sPAPRMachineState *sm,
>                                   target_ulong addr, target_ulong size,
>                                   sPAPROptionVector *ov5_updates);
> +void spapr_setup_hpt_and_vrma(sPAPRMachineState *spapr);
>  sPAPRTCETable *spapr_tce_new_table(DeviceState *owner, uint32_t liobn);
>  void spapr_tce_table_enable(sPAPRTCETable *tcet,
>                              uint32_t page_shift, uint64_t bus_offset,

-- 
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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