Re: [Qemu-devel] [PATCH 2/3] spapr: fix CAS-generated reset

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

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On Fri, Sep 08, 2017 at 04:33:43PM +0200, Cédric Le Goater wrote:
> The OV5_MMU_RADIX_300 requires special handling in the CAS negotiation
> process. It is cleared from the option vector of the guest before
> evaluating the changes and re-added later. But, when testing for a
> possible CAS reset :
> 
>     spapr->cas_reboot = spapr_ovec_diff(ov5_updates,
>                                         ov5_cas_old, spapr->ov5_cas);
> 
> the bit OV5_MMU_RADIX_300 will each time be seen as removed from the
> previous OV5 set, hence generating a reset loop.
> 
> Fix this problem by also clearing the same bit in the ov5_cas_old set.
> 
> Signed-off-by: Cédric Le Goater <clg@kaod.org>

Kind of an ugly hack, but probably the easiest fix for now. Applied to ppc-for-2.11.

> ---
>  hw/ppc/spapr_hcall.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> index 07b3da8dc4cd..92f1e21358b8 100644
> --- a/hw/ppc/spapr_hcall.c
> +++ b/hw/ppc/spapr_hcall.c
> @@ -1575,6 +1575,13 @@ static target_ulong h_client_architecture_support(PowerPCCPU *cpu,
>       * to worry about this for now.
>       */
>      ov5_cas_old = spapr_ovec_clone(spapr->ov5_cas);
> +
> +    /* also clear the radix/hash bit from the current ov5_cas bits to
> +     * be in sync with the newly ov5 bits. Else the radix bit will be
> +     * seen as being removed and this will generate a reset loop
> +     */
> +    spapr_ovec_clear(ov5_cas_old, OV5_MMU_RADIX_300);
> +
>      /* full range of negotiated ov5 capabilities */
>      spapr_ovec_intersect(spapr->ov5_cas, spapr->ov5, ov5_guest);
>      spapr_ovec_cleanup(ov5_guest);

-- 
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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