Re: [Qemu-devel] [RFC PATCH 5/9] spapr: Only setup HTP if necessary.

[David Gibson]

On Tue, Feb 07, 2017 at 01:56:48PM +1100, Sam Bobroff wrote:
> Because KVM cannot support radix and hash modes concurrently, QEMU can
> avoid allocating a hash page table if KVM supports radix mode.
> 
> Signed-off-by: Sam Bobroff <address@hidden>

This isn't quite right, it's doing the HPT handling based on whether
or not we *can* do RPT rather than whether we *are* doing RPT.

It'll mostly work for now, while only radix-on-radix and hash-on-hash
are supported, but that won't be true forever.

It will already be wrong if, for example, you tried to run a POWER8
TCG guest on a host that happened to be a POWER9 in radix mode.

> ---
>  hw/ppc/spapr.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index d629e2630c..1411e470c0 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1150,15 +1150,17 @@ static void ppc_spapr_reset(void)
>      /* Check for unknown sysbus devices */
>      foreach_dynamic_sysbus_device(find_unknown_sysbus_device, NULL);
>  
> -    /* Allocate and/or reset the hash page table */
> -    spapr_reallocate_hpt(spapr,
> +    if (!kvmppc_has_cap_mmu_radix()) {
> +        /* 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);
> +        /* Update the RMA size if necessary */
> +        if (spapr->vrma_adjust) {
> +            spapr->rma_size = kvmppc_rma_size(spapr_node0_size(),
> +                                              spapr->htab_shift);
> +        }
>      }
>  
>      qemu_devices_reset();

-- 
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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