Re: [Xen-devel] [PATCH] xen: do not unmask disabled IRQ on eoi.

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 15 Oct 2010, Ian Campbell wrote:
> On Fri, 2010-10-15 at 17:32 +0100, Ian Campbell wrote:
> > On Fri, 2010-10-15 at 17:12 +0100, Stefano Stabellini wrote:
> > > Reading a little bit more about the fasteoi handler, it seems to me that
> > > a better solution would be not to mask_evtchn and clear_evtchn in
> > > __xen_evtchn_do_upcall, but just clear_evtchn in the eoi handler.
> > > This would also be much more similar to the way the fasteoi handler is
> > > used by the ioapic chip.
> > > The appended patch has been only smoked tested.
> > 
> > Fails to boot dom0 for me.
> >         
> >         irq 20: nobody cared (try booting with the "irqpoll" option)
> >         Pid: 0, comm: swapper Not tainted 
> > 2.6.32.24-x86_32p-xen0-01025-g5238c00-dirty #205
> >         Call Trace:
> >          [<c1377034>] ? printk+0x18/0x1c
> >          [<c106f5c7>] __report_bad_irq+0x27/0x90
> >          [<c106f78e>] note_interrupt+0x15e/0x1a0
> >          [<c1169669>] ? _raw_spin_unlock+0x89/0xa0
> >          [<c106febc>] handle_fasteoi_irq+0xac/0xd0
> >          [<c11a6a5f>] __xen_evtchn_do_upcall+0x1cf/0x1f0
> >          [<c11a6ab8>] xen_evtchn_do_upcall+0x28/0x40
> >          [<c100b767>] xen_do_upcall+0x7/0xc
> >          [<c10013a7>] ? hypercall_page+0x3a7/0x1010
> >          [<c1007472>] ? xen_safe_halt+0x12/0x30
> >          [<c100397f>] xen_idle+0x5f/0x80
> >          [<c1009c49>] cpu_idle+0x49/0xa0
> >          [<c1007c40>] ? xen_save_fl_direct+0x0/0xd
> >          [<c135d913>] rest_init+0x53/0x60
> >          [<c1543975>] start_kernel+0x382/0x39f
> >          [<c15433be>] ? unknown_bootoption+0x0/0x1e4
> >          [<c154308f>] i386_start_kernel+0x7e/0xa8
> >          [<c1546471>] xen_start_kernel+0x561/0x5d5
> >         handlers:
> >         [<c1223500>] (ata_sff_interrupt+0x0/0xd0)
> >         [<c128b2b0>] (usb_hcd_irq+0x0/0xe0)
> >         Disabling IRQ #20
> >         
> > I think because you missed the pirq case.
> 
> Mixed the patch up with some other patch. Lets try that again...

Yes I did.  I think this version is better because in case the pirq is
already masked in pirq_eoi it makes sure that it stays that way, thus
preventing cases like the one you described before from happening.

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 175e931..9fb6e0f 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -441,16 +441,23 @@ static void pirq_eoi(unsigned int irq)
        struct irq_info *info = info_for_irq(irq);
        struct physdev_eoi eoi = { .irq = info->u.pirq.gsi };
        bool need_eoi;
+       struct shared_info *s = HYPERVISOR_shared_info;
+       int need_mask = 0;
 
        need_eoi = pirq_needs_eoi(irq);
 
-       if (!need_eoi || !pirq_eoi_does_unmask)
-               unmask_evtchn(info->evtchn);
+       if (need_eoi && pirq_eoi_does_unmask)
+               need_mask = sync_test_and_set_bit(info->evtchn, s->evtchn_mask);
 
        if (need_eoi) {
                int rc = HYPERVISOR_physdev_op(PHYSDEVOP_eoi, &eoi);
                WARN_ON(rc);
+
+               if (need_mask)
+                       mask_evtchn(info->evtchn);
        }
+
+       clear_evtchn(info->evtchn);
 }
 
 static void pirq_query_unmask(int irq)
@@ -1074,9 +1081,6 @@ static void __xen_evtchn_do_upcall(struct pt_regs *regs)
                                int irq = evtchn_to_irq[port];
                                struct irq_desc *desc;
 
-                               mask_evtchn(port);
-                               clear_evtchn(port);
-
                                if (irq != -1) {
                                        desc = irq_to_desc(irq);
                                        if (desc)
@@ -1202,7 +1206,7 @@ static void ack_dynirq(unsigned int irq)
        move_masked_irq(irq);
 
        if (VALID_EVTCHN(evtchn))
-               unmask_evtchn(evtchn);
+               clear_evtchn(evtchn);
 }
 
 static int retrigger_irq(unsigned int irq)
@@ -1384,7 +1388,6 @@ void xen_irq_resume(void)
 static struct irq_chip xen_dynamic_chip __read_mostly = {
        .name           = "xen-dyn",
 
-       .disable        = mask_irq,
        .mask           = mask_irq,
        .unmask         = unmask_irq,
 
@@ -1412,7 +1415,6 @@ static struct irq_chip xen_pirq_chip __read_mostly = {
        .enable         = pirq_eoi,
        .unmask         = unmask_irq,
 
-       .disable        = mask_irq,
        .mask           = mask_irq,
 
        .eoi            = ack_pirq,

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