Re: [Qemu-devel] [RFC PATCH v2 14/21] ppc/xive: add support for the SET_OS_PENDING command

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

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On Mon, Sep 11, 2017 at 07:12:28PM +0200, Cédric Le Goater wrote:
> Adjusting the Interrupt Pending Buffer for the O/S would allow a CPU
> to process event queues of other priorities during one physical
> interrupt cycle. This is not currently used by the XIVE support for
> sPAPR in Linux but it is by the hypervisor.
> 
> Signed-off-by: Cédric Le Goater <clg@kaod.org>
> ---
>  hw/intc/spapr_xive.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/intc/spapr_xive.c b/hw/intc/spapr_xive.c
> index ad3ff91b13ea..ad3f03e37401 100644
> --- a/hw/intc/spapr_xive.c
> +++ b/hw/intc/spapr_xive.c
> @@ -162,7 +162,14 @@ static bool spapr_xive_tm_is_readonly(uint8_t index)
>  static void spapr_xive_tm_write_special(ICPState *icp, hwaddr offset,
>                                    uint64_t value, unsigned size)
>  {
> -    /* TODO: support TM_SPC_SET_OS_PENDING */
> +    if (offset == TM_SPC_SET_OS_PENDING && size == 1) {
> +        icp->tima_os[TM_IPB] |= priority_to_ipb(value & 0xff);
> +        icp->tima_os[TM_PIPR] = ipb_to_pipr(icp->tima_os[TM_IPB]);

This only lets the cpu raise bits in the IPB, never clear them.  Is
that right?  I don't see how you'd implement the handling of multiple
priorities without being able to clear bits here.

> +        spapr_xive_icp_notify(icp);
> +    } else {
> +        qemu_log_mask(LOG_GUEST_ERROR, "XIVE: invalid TIMA write @%"
> +                      HWADDR_PRIx" size %d\n", offset, size);
> +    }
>  
>      /* TODO: support TM_SPC_ACK_OS_EL */
>  }

-- 
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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