Re: [Qemu-devel] [PATCH 1/1] target/ppc: correct htab shift for hash on radix

[David Gibson]

On Mon, Nov 06, 2017 at 02:14:35PM +1100, Sam Bobroff wrote:
> KVM HV will soon support running a guest in hash mode on a POWER9 host
> running in radix mode (see [1]), however the guest currently fails to
> boot.
> 
> This is because the "htab_shift" value (the size of the MMU's hash
> table) is added to the device tree before KVM has had a chance to
> change it. If the host is in hash mode, KVM does not need to change it
> and so the problem is not seen, but when the host is in radix mode a
> change is required and we see a problem.
> 
> To fix this, move the call spapr_setup_hpt_and_vrma() (where
> htab_shift could be changed) up a little so that it's called before
> spapr_h_cas_compose_response() (where htab_shift is added to the
> device tree).
> 
> Signed-off-by: Sam Bobroff <address@hidden>

Applied to ppc-for-2.11.

> 
> [1] See http://www.spinics.net/lists/kvm-ppc/msg13057.html
> ---
> I tested this patch using a kernel based on Paul's kvm-ppc-next branch from 
> his
> powerpc tree:
> https://git.kernel.org/pub/scm/linux/kernel/git/paulus/powerpc.git/
> 
>  hw/ppc/spapr_hcall.c | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> index 0d59d1534d..be22a6b289 100644
> --- a/hw/ppc/spapr_hcall.c
> +++ b/hw/ppc/spapr_hcall.c
> @@ -1636,6 +1636,12 @@ static target_ulong 
> h_client_architecture_support(PowerPCCPU *cpu,
>      spapr->cas_legacy_guest_workaround = !spapr_ovec_test(ov1_guest,
>                                                            OV1_PPC_3_00);
>      if (!spapr->cas_reboot) {
> +        /* If ppc_spapr_reset() did not set up a HPT but one is necessary
> +         * (because the guest isn't going to use radix) then set it up here. 
> */
> +        if ((spapr->patb_entry & PATBE1_GR) && !guest_radix) {
> +            /* legacy hash or new hash: */
> +            spapr_setup_hpt_and_vrma(spapr);
> +        }
>          spapr->cas_reboot =
>              (spapr_h_cas_compose_response(spapr, args[1], args[2],
>                                            ov5_updates) != 0);
> @@ -1644,13 +1650,6 @@ static target_ulong 
> h_client_architecture_support(PowerPCCPU *cpu,
>  
>      if (spapr->cas_reboot) {
>          qemu_system_reset_request(SHUTDOWN_CAUSE_GUEST_RESET);
> -    } else {
> -        /* If ppc_spapr_reset() did not set up a HPT but one is necessary
> -         * (because the guest isn't going to use radix) then set it up here. 
> */
> -        if ((spapr->patb_entry & PATBE1_GR) && !guest_radix) {
> -            /* legacy hash or new hash: */
> -            spapr_setup_hpt_and_vrma(spapr);
> -        }
>      }
>  
>      return H_SUCCESS;

-- 
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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