x86: eliminate hard-coded NR_IRQS

... splitting it into global nr_irqs (determined at boot time) and
per- domain nr_pirqs (derived from nr_irqs and a possibly command line
specified value, which probably should later become a per-domain
config setting).

This has the (desirable imo) side effect of reducing the size of
struct hvm_irq_dpci from requiring an order-3 page to order-2 (on
x86-64), which nevertheless still is too large.

However, there is now a variable size bit array on the stack in
pt_irq_time_out() - while for the moment this probably is okay, it
certainly doesn't look nice. However, replacing this with a static
(pre-)allocation also seems less than ideal, because that would
require at least min(d->nr_pirqs, NR_VECTORS) bit arrays of
d->nr_pirqs bits, since this bit array is used outside of the
serialized code region in that function, and keeping the domain's
event lock acquired across pirq_guest_eoi() doesn't look like a good
idea either.

The IRQ- and vector-indexed arrays hanging off struct hvm_irq_dpci
could in fact be changed further to dynamically use the smaller of the
two ranges for indexing, since there are other assumptions about a
one-to-one relationship between IRQs and vectors here and elsewhere.

Additionally, it seems to me that struct hvm_mirq_dpci_mapping's
digl_list and gmsi fields could really be overlayed, which would yield
significant savings since this structure gets always instanciated in
form of d->nr_pirqs (as per the above could also be the smaller of
this and NR_VECTORS) dimensioned arrays.

Signed-off-by: Jan Beulich <jbeulich@novell.com>

3 files changed, 29 insertions, 6 deletions

diff --git a/xen/common/domain.c b/xen/common/domain.c
index 66694168a2..1d3b4d6b58 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -8,6 +8,7 @@
 #include <xen/compat.h>
 #include <xen/init.h>
 #include <xen/lib.h>
+#include <xen/ctype.h>
 #include <xen/errno.h>
 #include <xen/sched.h>
 #include <xen/domain.h>
@@ -198,6 +199,16 @@ struct vcpu *alloc_idle_vcpu(unsigned int cpu_id)
     return v;
 }
 
+static unsigned int extra_dom0_irqs, extra_domU_irqs = 8;
+static void __init parse_extra_guest_irqs(const char *s)
+{
+    if ( isdigit(*s) )
+        extra_domU_irqs = simple_strtoul(s, &s, 0);
+    if ( *s == ',' && isdigit(*++s) )
+        extra_dom0_irqs = simple_strtoul(s, &s, 0);
+}
+custom_param("extra_guest_irqs", parse_extra_guest_irqs);
+
 struct domain *domain_create(
     domid_t domid, unsigned int domcr_flags, ssidref_t ssidref)
 {
@@ -244,9 +255,19 @@ struct domain *domain_create(
         d->is_paused_by_controller = 1;
         atomic_inc(&d->pause_count);
 
+        d->nr_pirqs = nr_irqs +
+                      (domid ? extra_domU_irqs :
+                               extra_dom0_irqs ?: nr_irqs);
         if ( evtchn_init(d) != 0 )
             goto fail;
         init_status |= INIT_evtchn;
+        d->pirq_to_evtchn = xmalloc_array(u16, d->nr_pirqs);
+        d->pirq_mask = xmalloc_array(unsigned long,
+                                     BITS_TO_LONGS(d->nr_pirqs));
+        if ( !d->pirq_to_evtchn || !d->pirq_mask )
+            goto fail;
+        memset(d->pirq_to_evtchn, 0, d->nr_pirqs * sizeof(*d->pirq_to_evtchn));
+        bitmap_zero(d->pirq_mask, d->nr_pirqs);
 
         if ( grant_table_create(d) != 0 )
             goto fail;
@@ -289,7 +310,11 @@ struct domain *domain_create(
     if ( init_status & INIT_gnttab )
         grant_table_destroy(d);
     if ( init_status & INIT_evtchn )
+    {
+        xfree(d->pirq_mask);
+        xfree(d->pirq_to_evtchn);
         evtchn_destroy(d);
+    }
     if ( init_status & INIT_rangeset )
         rangeset_domain_destroy(d);
     if ( init_status & INIT_xsm )
diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index 4a8df90101..29e3885de2 100644
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -774,16 +774,14 @@ long do_domctl(XEN_GUEST_HANDLE(xen_domctl_t) u_domctl)
         struct domain *d;
         unsigned int pirq = op->u.irq_permission.pirq;
 
-        ret = -EINVAL;
-        if ( pirq >= NR_IRQS )
-            break;
-
         ret = -ESRCH;
         d = rcu_lock_domain_by_id(op->domain);
         if ( d == NULL )
             break;
 
-        if ( op->u.irq_permission.allow_access )
+        if ( pirq >= d->nr_pirqs )
+            ret = -EINVAL;
+        else if ( op->u.irq_permission.allow_access )
             ret = irq_permit_access(d, pirq);
         else
             ret = irq_deny_access(d, pirq);
diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
index 3f36d09e83..c51fd10031 100644
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -302,7 +302,7 @@ static long evtchn_bind_pirq(evtchn_bind_pirq_t *bind)
     int            port, pirq = bind->pirq;
     long           rc;
 
-    if ( (pirq < 0) || (pirq >= ARRAY_SIZE(d->pirq_to_evtchn)) )
+    if ( (pirq < 0) || (pirq >= d->nr_pirqs) )
         return -EINVAL;
 
     if ( !irq_access_permitted(d, pirq) )