[XenPPC] [PATCH] Make Linux bail out of IPI vector reset

[Amos Waterland <apw@xxxxxxxxxx>]

Xen/PPC currently shares the mpic with dom0 Linux.  In order for
interprocessor interrupts to work, we cannot allow Linux to reset the
mpic (a patch for the latter was already merged) nor to reset the IPI
vectors and change their priority.

This patch introduces a feature flag, rather than trying to code a new
function called xen_mpic_init and duplicating all the associated
machinery it pulls in.  I tried the first approach, and it results in a
lot of code duplication, which is a worse maintenence burden than this,
I believe.  Jimi may not like this approach, but I believe it is the
best solution until we completely virtualize the PIC at some point in
the future.

Signed-off-by: Amos Waterland <apw@xxxxxxxxxx>

---

 arch/powerpc/platforms/xen/evtchn.c |    1 +
 arch/powerpc/sysdev/mpic.c          |    4 ++++
 include/asm-powerpc/mpic.h          |    2 ++
 3 files changed, 7 insertions(+)

diff -r 4e5b95219939 arch/powerpc/platforms/xen/evtchn.c
--- a/arch/powerpc/platforms/xen/evtchn.c       Mon Nov 20 12:35:47 2006 -0500
+++ b/arch/powerpc/platforms/xen/evtchn.c       Tue Nov 21 20:53:20 2006 -0500
@@ -101,6 +101,7 @@ static __init struct mpic *xen_share_map
 
        mpic = mpic_alloc(opic_addr,
                          MPIC_PRIMARY | MPIC_BIG_ENDIAN |
+                         MPIC_SKIP_IPI_INIT |
                          MPIC_BROKEN_U3 /* | MPIC_WANTS_RESET */,
                          0, 0, 128, 128, senses, 128, "Xen-U3-MPIC");
        BUG_ON(mpic == NULL);
diff -r 4e5b95219939 arch/powerpc/sysdev/mpic.c
--- a/arch/powerpc/sysdev/mpic.c        Mon Nov 20 12:35:47 2006 -0500
+++ b/arch/powerpc/sysdev/mpic.c        Tue Nov 21 21:08:32 2006 -0500
@@ -741,6 +741,9 @@ void __init mpic_init(struct mpic *mpic)
                           (MPIC_VEC_TIMER_0 + i));
        }
 
+        if (mpic->flags & MPIC_SKIP_IPI_INIT)
+                goto ipi_bailout;
+
        /* Initialize IPIs to our reserved vectors and mark them disabled for 
now */
        mpic_test_broken_ipi(mpic);
        for (i = 0; i < 4; i++) {
@@ -756,6 +759,7 @@ void __init mpic_init(struct mpic *mpic)
 #endif /* CONFIG_SMP */
        }
 
+ ipi_bailout:
        /* Initialize interrupt sources */
        if (mpic->irq_count == 0)
                mpic->irq_count = mpic->num_sources;
diff -r 4e5b95219939 include/asm-powerpc/mpic.h
--- a/include/asm-powerpc/mpic.h        Mon Nov 20 12:35:47 2006 -0500
+++ b/include/asm-powerpc/mpic.h        Tue Nov 21 20:53:20 2006 -0500
@@ -190,6 +190,8 @@ struct mpic
 #define MPIC_BROKEN_IPI                        0x00000008
 /* MPIC wants a reset */
 #define MPIC_WANTS_RESET               0x00000010
+/* Skip reset of IPI vectors during init */
+#define MPIC_SKIP_IPI_INIT             0x00000020
 
 /* Allocate the controller structure and setup the linux irq descs
  * for the range if interrupts passed in. No HW initialization is

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