Re: [PATCH 11/13] pnv/xive: Update PIPR when updating CPPR

["Cédric Le Goater" <clg@kaod.org>]

On 8/1/24 22:30, Michael Kowal wrote:
> From: Glenn Miles <milesg@linux.vnet.ibm.com>
> 
> Current code was updating the PIPR inside the xive_tctx_accept() function
> instead of the xive_tctx_set_cppr function, which is where the HW would
> have it updated.
> 
> Moved the update to the xive_tctx_set_cppr function which required
> additional support for pool interrupts.
> 
> Signed-off-by: Glenn Miles <milesg@linux.vnet.ibm.com>
> Signed-off-by: Michael Kowal <kowal@linux.ibm.com>
> ---
>   hw/intc/xive.c | 34 ++++++++++++++++++++++++++++++++--
>   1 file changed, 32 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/intc/xive.c b/hw/intc/xive.c
> index 5c4ca7f6e0..d951aac3a0 100644
> --- a/hw/intc/xive.c
> +++ b/hw/intc/xive.c
> @@ -89,7 +89,6 @@ static uint64_t xive_tctx_accept(XiveTCTX *tctx, uint8_t ring)
>   
>           /* Reset the pending buffer bit */
>           aregs[TM_IPB] &= ~xive_priority_to_ipb(cppr);
> -        regs[TM_PIPR] = ipb_to_pipr(aregs[TM_IPB]);
>   
>           /* Drop Exception bit */
>           regs[TM_NSR] &= ~mask;
> @@ -143,6 +142,8 @@ void xive_tctx_reset_signal(XiveTCTX *tctx, uint8_t ring)
>   static void xive_tctx_set_cppr(XiveTCTX *tctx, uint8_t ring, uint8_t cppr)
>   {
>       uint8_t *regs = &tctx->regs[ring];
> +    uint8_t pipr_min;
> +    uint8_t ring_min;
>   
>       trace_xive_tctx_set_cppr(tctx->cs->cpu_index, ring,
>                                regs[TM_IPB], regs[TM_PIPR],
> @@ -154,8 +155,37 @@ static void xive_tctx_set_cppr(XiveTCTX *tctx, uint8_t ring, uint8_t cppr)
>   
>       tctx->regs[ring + TM_CPPR] = cppr;
>   
> +    /*
> +     * Recompute the PIPR based on local pending interrupts.  The PHYS
> +     * ring must take the minimum of both the PHYS and POOL PIPR values.
> +     */
> +    pipr_min = ipb_to_pipr(regs[TM_IPB]);
> +    ring_min = ring;
> +
> +    /* PHYS updates also depend on POOL values */
> +    if (ring == TM_QW3_HV_PHYS) {
> +        uint8_t *pregs = &tctx->regs[TM_QW2_HV_POOL];

'pool_regs' would be clearer

> +
> +        /* POOL values only matter if POOL ctx is valid */
> +        if (pregs[TM_WORD2] & 0x80) {
> +
> +            uint8_t pool_pipr = ipb_to_pipr(pregs[TM_IPB]);
> +
> +            /*
> +             * Determine highest priority interrupt and
> +             * remember which ring has it.
> +             */
> +            if (pool_pipr < pipr_min) {
> +                pipr_min = pool_pipr;
> +                ring_min = TM_QW2_HV_POOL;
> +            }
> +        }
> +    }
> +
> +    regs[TM_PIPR] = pipr_min;
> +
>       /* CPPR has changed, check if we need to raise a pending exception */
> -    xive_tctx_notify(tctx, ring);
> +    xive_tctx_notify(tctx, ring_min);
>   }
>   
>   void xive_tctx_ipb_update(XiveTCTX *tctx, uint8_t ring, uint8_t ipb)