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

[David Gibson]

On Mon, Nov 26, 2018 at 12:20:19PM +0100, Cédric Le Goater wrote:
> On 11/26/18 6:39 AM, David Gibson wrote:
> > 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.
> 
> It still can be through the ESB MMIOs, if the guest does a load on the 
> trigger page.

Oh, good point.  That makes me rethink all my comments on this matter.

In that case I think your original code was fine, except that I'd
prefer to see the setting of the ASSERTED bit inside the trigger
function, instead of in the set_irq() caller.


> 
> C.
> 
>  
> > 
> >> +        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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