Re: [Qemu-devel] [PATCH v5 02/36] ppc/xive: add support for the LSI interrupt sources

[David Gibson]

On Fri, Nov 23, 2018 at 02:28:35PM +0100, Cédric Le Goater wrote:
> 
> >>>> +/*
> >>>> + * Returns whether the event notification should be forwarded.
> >>>> + */
> >>>> +static bool xive_source_lsi_trigger(XiveSource *xsrc, uint32_t
> >>>> srcno)
> >>>
> >>> What exactly "trigger" means isn't entirely obvious for an LSI.  Might
> >>> be clearer to have "lsi_assert" and "lsi_deassert" helpers instead.
> >>
> >> This is called only when the interrupt is asserted. So it is a 
> >> simplified LSI trigger depending only on the 'P' bit.
> > 
> > Yes, I see that.  But the result is that while the MSI logic is
> > encapsulated in the MSI trigger function, this leaves the LSI logic
> > split across the trigger function and set_irq() itself. I think it 
> > would be better to have assert and deassert helpers instead, which
> > handle both the trigger/notification and also the updating of the
> > ASSERTED bit.
> 
> Something like the xive_source_set_irq_lsi() below ?

Uh.. not exactly what I had in mind, but close enough.

[snip]
+/*
> + * Returns whether the event notification should be forwarded.
> + */
>  static bool xive_source_esb_trigger(XiveSource *xsrc, uint32_t srcno)
>  {
> +    bool notify;
> +
>      assert(srcno < xsrc->nr_irqs);
>  
> -    return xive_esb_trigger(&xsrc->status[srcno]);
> +    notify = xive_esb_trigger(&xsrc->status[srcno]);
> +
> +    if (xive_source_irq_is_lsi(xsrc, srcno) &&

Except that this block can go, since this function is no longer called
for LSIs.

> +        xive_source_esb_get(xsrc, srcno) == XIVE_ESB_QUEUED) {
> +        qemu_log_mask(LOG_GUEST_ERROR,
> +                      "XIVE: queued an event on LSI IRQ %d\n", srcno);
> +    }
> +
> +    return notify;
>  }
>  
>  /*
> @@ -103,9 +127,22 @@ static bool xive_source_esb_trigger(Xive
>   */
>  static bool xive_source_esb_eoi(XiveSource *xsrc, uint32_t srcno)
>  {
> +    bool notify;
> +
>      assert(srcno < xsrc->nr_irqs);
>  
> -    return xive_esb_eoi(&xsrc->status[srcno]);
> +    notify = xive_esb_eoi(&xsrc->status[srcno]);
> +
> +    /* LSI sources do not set the Q bit but they can still be
> +     * asserted, in which case we should forward a new event
> +     * notification
> +     */
> +    if (xive_source_irq_is_lsi(xsrc, srcno)) {
> +        bool level = xsrc->status[srcno] & XIVE_STATUS_ASSERTED;
> +        notify = xive_source_set_irq_lsi(xsrc, srcno, level);
> +    }
> +
> +    return notify;
>  }
>  
>  /*
> @@ -268,8 +305,12 @@ static void xive_source_set_irq(void *op
>      XiveSource *xsrc = XIVE_SOURCE(opaque);
>      bool notify = false;
>  
> -    if (val) {
> -        notify = xive_source_esb_trigger(xsrc, srcno);
> +    if (xive_source_irq_is_lsi(xsrc, srcno)) {
> +        notify = xive_source_set_irq_lsi(xsrc, srcno, val);
> +    } else {
> +        if (val) {
> +            notify = xive_source_esb_trigger(xsrc, srcno);
> +        }
>      }
>  
>      /* Forward the source event notification for routing */
> @@ -289,9 +330,11 @@ void xive_source_pic_print_info(XiveSour
>              continue;
>          }
>  
> -        monitor_printf(mon, "  %08x %c%c\n", i + offset,
> +        monitor_printf(mon, "  %08x %s %c%c%c\n", i + offset,
> +                       xive_source_irq_is_lsi(xsrc, i) ? "LSI" : "MSI",
>                         pq & XIVE_ESB_VAL_P ? 'P' : '-',
> -                       pq & XIVE_ESB_VAL_Q ? 'Q' : '-');
> +                       pq & XIVE_ESB_VAL_Q ? 'Q' : '-',
> +                       xsrc->status[i] & XIVE_STATUS_ASSERTED ? 'A' : ' ');
>      }
>  }
>  
> @@ -299,6 +342,8 @@ static void xive_source_reset(DeviceStat
>  {
>      XiveSource *xsrc = XIVE_SOURCE(dev);
>  
> +    /* Do not clear the LSI bitmap */
> +
>      /* PQs are initialized to 0b01 which corresponds to "ints off" */
>      memset(xsrc->status, 0x1, xsrc->nr_irqs);
>  }
> @@ -324,6 +369,7 @@ static void xive_source_realize(DeviceSt
>                                       xsrc->nr_irqs);
>  
>      xsrc->status = g_malloc0(xsrc->nr_irqs);
> +    xsrc->lsi_map = bitmap_new(xsrc->nr_irqs);
>  
>      memory_region_init_io(&xsrc->esb_mmio, OBJECT(xsrc),
>                            &xive_source_esb_ops, xsrc, "xive.esb",
> 

-- 
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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