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

[Cédric Le Goater]

On 09/10/2017 05:17 AM, David Gibson wrote:
> 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 <address@hidden>
> 
> Kind of an ugly hack,  

yes. I lack context to fully understand why the guest radix option is
handled that way. 

> but probably the easiest fix for now. Applied to ppc-for-2.11.

Thanks,

C.

> 
>> ---
>>  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);
>