[PATCH] arm: support fewer LRs register than virtual irqs

[Stefano Stabellini <stefano.stabellini@eu.citrix.com>]

If the vgic needs to inject a virtual irq into the guest, but no free
LR registers are available, add the irq to a list and return.
Whenever an LR register becomes available we add the queued irq to it
and remove it from the list.
We use the gic lock to protect the list and the bitmask.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
---
 xen/arch/arm/gic.c           |   46 +++++++++++++++++++++++++++++++++++++----
 xen/include/asm-arm/domain.h |    1 +
 2 files changed, 42 insertions(+), 5 deletions(-)

diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index adc10bb..97c223c 100644
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -25,6 +25,7 @@
 #include <xen/sched.h>
 #include <xen/errno.h>
 #include <xen/softirq.h>
+#include <xen/list.h>
 #include <asm/p2m.h>
 #include <asm/domain.h>
 
@@ -45,6 +46,8 @@ static struct {
     unsigned int lines;
     unsigned int cpus;
     spinlock_t lock;
+    uint64_t lr_mask;
+    struct list_head lr_pending;
 } gic;
 
 irq_desc_t irq_desc[NR_IRQS];
@@ -247,6 +250,8 @@ static void __cpuinit gic_hyp_init(void)
 
     GICH[GICH_HCR] = GICH_HCR_EN;
     GICH[GICH_MISR] = GICH_MISR_EOI;
+    gic.lr_mask = 0ULL;
+    INIT_LIST_HEAD(&gic.lr_pending);
 }
 
 /* Set up the GIC */
@@ -345,16 +350,35 @@ int __init setup_irq(unsigned int irq, struct irqaction *new)
     return rc;
 }
 
-void gic_set_guest_irq(unsigned int virtual_irq,
+static inline void gic_set_lr(int lr, unsigned int virtual_irq,
         unsigned int state, unsigned int priority)
 {
-    BUG_ON(virtual_irq > nr_lrs);
-    GICH[GICH_LR + virtual_irq] = state |
+    BUG_ON(lr > nr_lrs);
+    GICH[GICH_LR + lr] = state |
         GICH_LR_MAINTENANCE_IRQ |
         ((priority >> 3) << GICH_LR_PRIORITY_SHIFT) |
         ((virtual_irq & GICH_LR_VIRTUAL_MASK) << GICH_LR_VIRTUAL_SHIFT);
 }
 
+void gic_set_guest_irq(unsigned int virtual_irq,
+        unsigned int state, unsigned int priority)
+{
+    int i;
+
+    spin_lock(&gic.lock);
+    for (i = 0; i < nr_lrs; i++) {
+        if (!test_and_set_bit(i, &gic.lr_mask))
+        {
+            gic_set_lr(i, virtual_irq, state, priority);
+            spin_unlock(&gic.lock);
+            return;
+        }
+    }
+    list_add_tail(&irq_to_pending(current, virtual_irq)->lr_link, &gic.lr_pending);
+    spin_unlock(&gic.lock);
+    return;
+}
+
 void gic_inject_irq_start(void)
 {
     uint32_t hcr;
@@ -435,13 +459,26 @@ static void maintenance_interrupt(int irq, void *dev_id, struct cpu_user_regs *r
     uint32_t lr;
     uint64_t eisr = GICH[GICH_EISR0] | (((uint64_t) GICH[GICH_EISR1]) << 32);
 
-    for ( i = 0; i < 64; i++ ) {
+    for ( i = 0; i < nr_lrs; i++ ) {
         if ( eisr & ((uint64_t)1 << i) ) {
             struct pending_irq *p;
 
+            spin_lock(&gic.lock);
             lr = GICH[GICH_LR + i];
             virq = lr & GICH_LR_VIRTUAL_MASK;
             GICH[GICH_LR + i] = 0;
+            clear_bit(i, &gic.lr_mask);
+
+            if ( !list_empty(gic.lr_pending.next) ) {
+                p = list_entry(gic.lr_pending.next, typeof(*p), lr_link);
+                gic_set_lr(i, p->irq, GICH_LR_PENDING, p->priority);
+                list_del(&p->lr_link);
+                INIT_LIST_HEAD(&p->lr_link);
+                set_bit(i, &gic.lr_mask);
+            } else {
+                gic_inject_irq_stop();
+            }
+            spin_unlock(&gic.lock);
 
             spin_lock(&current->arch.vgic.lock);
             p = irq_to_pending(current, virq);
@@ -449,7 +486,6 @@ static void maintenance_interrupt(int irq, void *dev_id, struct cpu_user_regs *r
                 p->desc->status &= ~IRQ_INPROGRESS;
                 GICC[GICC_DIR] = virq;
             }
-            gic_inject_irq_stop();
             list_del(&p->link);
             INIT_LIST_HEAD(&p->link);
             cpu_raise_softirq(current->processor, VGIC_SOFTIRQ);
diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
index 3372d14..75095ff 100644
--- a/xen/include/asm-arm/domain.h
+++ b/xen/include/asm-arm/domain.h
@@ -21,6 +21,7 @@ struct pending_irq
     struct irq_desc *desc; /* only set it the irq corresponds to a physical irq */
     uint8_t priority;
     struct list_head link;
+    struct list_head lr_link;
 };
 
 struct arch_domain
-- 
1.7.8.3