Re: [Qemu-ppc] [RFC PATCH 16/26] ppc/xive: notify CPU when interrupt priority is more privileged

[Cédric Le Goater]

On 09/09/2017 09:39 AM, Benjamin Herrenschmidt wrote:
> On Wed, 2017-07-05 at 19:13 +0200, Cédric Le Goater wrote:
>> Signed-off-by: Cédric Le Goater <address@hidden>
>> ---
>>  hw/intc/xive.c | 21 +++++++++++++++++++++
>>  1 file changed, 21 insertions(+)
>>
>> diff --git a/hw/intc/xive.c b/hw/intc/xive.c
>> index c3c1e9c9db2d..cda1fa18e44d 100644
>> --- a/hw/intc/xive.c
>> +++ b/hw/intc/xive.c
>> @@ -53,6 +53,21 @@ static uint64_t xive_icp_accept(XiveICPState *xicp)
>>      return (nsr << 8) | xicp->tima_os[TM_CPPR];
>>  }
>>  
>> +static uint8_t ipb_to_pipr(uint8_t ibp)
>> +{
>> +    return ibp ? clz32((uint32_t)ibp << 24) : 0xff;
>> +}
> 
> The PIPR needs to be updated also on accept etc... anything that change
> IPBs or CPPR really.

I did forget the update in accept ... thanks. 

> Also I just learned something from the designers: The IPIR is clamped
> to CPPR.
> 
> So basically the value in the PIPR is:
> 
>       v = leftmost_bit_of(ipb) (or 0xff);
>       pipr = v < cppr ? v : cppr;
> 
> which means it's never actually 0xff ... surprise !

ah. that is not what the specs say but it shouldn't be a problem.
I will change the code to reflect that.

C.

> That also means I need to fix my implementation of H_IPOLL in KVM.
> 
>> +static void xive_icp_notify(XiveICPState *xicp)
>> +{
>> +    xicp->tima_os[TM_PIPR] = ipb_to_pipr(xicp->tima_os[TM_IPB]);
>> +
>> +    if (xicp->tima_os[TM_PIPR] < xicp->tima_os[TM_CPPR]) {
>> +        xicp->tima_os[TM_NSR] |= TM_QW1_NSR_EO;
>> +        qemu_irq_raise(ICP(xicp)->output);
>> +    }
>> +}
>> +
>>  static void xive_icp_set_cppr(XiveICPState *xicp, uint8_t cppr)
>>  {
>>      if (cppr > XIVE_PRIORITY_MAX) {
>> @@ -60,6 +75,10 @@ static void xive_icp_set_cppr(XiveICPState *xicp, uint8_t 
>> cppr)
>>      }
>>  
>>      xicp->tima_os[TM_CPPR] = cppr;
>> +
>> +    /* CPPR has changed, inform the ICP which might raise an
>> +     * exception */
>> +    xive_icp_notify(xicp);
>>  }
>>  
>>  /*
>> @@ -339,6 +358,8 @@ static void xive_icp_irq(XiveICSState *xs, int lisn)
>>      } else {
>>          qemu_log_mask(LOG_UNIMP, "XIVE: w7 format1 not implemented\n");
>>      }
>> +
>> +    xive_icp_notify(xicp);
>>  }
>>  
>>  /*