[RFC PATCH 08/24] ARM: GICv3: introduce separate pending_irq structs for LPIs

[Andre Przywara <andre.przywara@arm.com>]

For the same reason that allocating a struct irq_desc for each
possible LPI is not an option, having a struct pending_irq for each LPI
is also not feasible. However we actually only need those when an
interrupt is on a vCPU (or is about to be injected).
Maintain a list of those structs that we can use for the lifecycle of
a guest LPI. We allocate new entries if necessary, however reuse
pre-owned entries whenever possible.
Teach the existing VGIC functions to find the right pointer when being
given a virtual LPI number.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
---
 xen/arch/arm/gic.c            |  3 +++
 xen/arch/arm/vgic-v3.c        |  2 ++
 xen/arch/arm/vgic.c           | 56 ++++++++++++++++++++++++++++++++++++++++---
 xen/include/asm-arm/domain.h  |  1 +
 xen/include/asm-arm/gic-its.h | 10 ++++++++
 xen/include/asm-arm/vgic.h    |  9 +++++++
 6 files changed, 78 insertions(+), 3 deletions(-)

diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index 63c744a..ebe4035 100644
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -506,6 +506,9 @@ static void gic_update_one_lr(struct vcpu *v, int i)
                 struct vcpu *v_target = vgic_get_target_vcpu(v, irq);
                 irq_set_affinity(p->desc, cpumask_of(v_target->processor));
             }
+            /* If this was an LPI, mark this struct as available again. */
+            if ( p->irq >= 8192 )
+                p->irq = 0;
         }
     }
 }
diff --git a/xen/arch/arm/vgic-v3.c b/xen/arch/arm/vgic-v3.c
index ec038a3..e9b6490 100644
--- a/xen/arch/arm/vgic-v3.c
+++ b/xen/arch/arm/vgic-v3.c
@@ -1388,6 +1388,8 @@ static int vgic_v3_vcpu_init(struct vcpu *v)
     if ( v->vcpu_id == last_cpu || (v->vcpu_id == (d->max_vcpus - 1)) )
         v->arch.vgic.flags |= VGIC_V3_RDIST_LAST;
 
+    INIT_LIST_HEAD(&v->arch.vgic.pending_lpi_list);
+
     return 0;
 }
 
diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
index 0965119..b961551 100644
--- a/xen/arch/arm/vgic.c
+++ b/xen/arch/arm/vgic.c
@@ -31,6 +31,8 @@
 #include <asm/mmio.h>
 #include <asm/gic.h>
 #include <asm/vgic.h>
+#include <asm/gic_v3_defs.h>
+#include <asm/gic-its.h>
 
 static inline struct vgic_irq_rank *vgic_get_rank(struct vcpu *v, int rank)
 {
@@ -61,7 +63,7 @@ struct vgic_irq_rank *vgic_rank_irq(struct vcpu *v, unsigned int irq)
     return vgic_get_rank(v, rank);
 }
 
-static void vgic_init_pending_irq(struct pending_irq *p, unsigned int virq)
+void vgic_init_pending_irq(struct pending_irq *p, unsigned int virq)
 {
     INIT_LIST_HEAD(&p->inflight);
     INIT_LIST_HEAD(&p->lr_queue);
@@ -244,10 +246,14 @@ struct vcpu *vgic_get_target_vcpu(struct vcpu *v, unsigned int virq)
 
 static int vgic_get_virq_priority(struct vcpu *v, unsigned int virq)
 {
-    struct vgic_irq_rank *rank = vgic_rank_irq(v, virq);
+    struct vgic_irq_rank *rank;
     unsigned long flags;
     int priority;
 
+    if ( virq >= 8192 )
+        return gicv3_lpi_get_priority(v->domain, virq);
+
+    rank = vgic_rank_irq(v, virq);
     vgic_lock_rank(v, rank, flags);
     priority = rank->priority[virq & INTERRUPT_RANK_MASK];
     vgic_unlock_rank(v, rank, flags);
@@ -446,13 +452,55 @@ int vgic_to_sgi(struct vcpu *v, register_t sgir, enum gic_sgi_mode irqmode, int
     return 1;
 }
 
+/*
+ * Holding struct pending_irq's for each possible virtual LPI in each domain
+ * requires too much Xen memory, also a malicious guest could potentially
+ * spam Xen with LPI map requests. We cannot cover those with (guest allocated)
+ * ITS memory, so we use a dynamic scheme of allocating struct pending_irq's
+ * on demand.
+ */
+struct pending_irq *lpi_to_pending(struct vcpu *v, unsigned int lpi,
+                                   bool allocate)
+{
+    struct lpi_pending_irq *lpi_irq, *empty = NULL;
+
+    /* TODO: locking! */
+    list_for_each_entry(lpi_irq, &v->arch.vgic.pending_lpi_list, entry)
+    {
+        if ( lpi_irq->pirq.irq == lpi )
+            return &lpi_irq->pirq;
+
+        if ( lpi_irq->pirq.irq == 0 && !empty )
+            empty = lpi_irq;
+    }
+
+    if ( !allocate )
+        return NULL;
+
+    if ( !empty )
+    {
+        empty = xzalloc(struct lpi_pending_irq);
+        vgic_init_pending_irq(&empty->pirq, lpi);
+        list_add_tail(&empty->entry, &v->arch.vgic.pending_lpi_list);
+    } else
+    {
+        empty->pirq.status = 0;
+        empty->pirq.irq = lpi;
+    }
+
+    return &empty->pirq;
+}
+
 struct pending_irq *irq_to_pending(struct vcpu *v, unsigned int irq)
 {
     struct pending_irq *n;
+
     /* Pending irqs allocation strategy: the first vgic.nr_spis irqs
      * are used for SPIs; the rests are used for per cpu irqs */
     if ( irq < 32 )
         n = &v->arch.vgic.pending_irqs[irq];
+    else if ( irq >= 8192 )
+        n = lpi_to_pending(v, irq, true);
     else
         n = &v->domain->arch.vgic.pending_irqs[irq - 32];
     return n;
@@ -480,7 +528,7 @@ void vgic_clear_pending_irqs(struct vcpu *v)
 void vgic_vcpu_inject_irq(struct vcpu *v, unsigned int virq)
 {
     uint8_t priority;
-    struct pending_irq *iter, *n = irq_to_pending(v, virq);
+    struct pending_irq *iter, *n;
     unsigned long flags;
     bool_t running;
 
@@ -488,6 +536,8 @@ void vgic_vcpu_inject_irq(struct vcpu *v, unsigned int virq)
 
     spin_lock_irqsave(&v->arch.vgic.lock, flags);
 
+    n = irq_to_pending(v, virq);
+
     /* vcpu offline */
     if ( test_bit(_VPF_down, &v->pause_flags) )
     {
diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
index 9452fcd..ae8a9de 100644
--- a/xen/include/asm-arm/domain.h
+++ b/xen/include/asm-arm/domain.h
@@ -249,6 +249,7 @@ struct arch_vcpu
         paddr_t rdist_base;
 #define VGIC_V3_RDIST_LAST  (1 << 0)        /* last vCPU of the rdist */
         uint8_t flags;
+        struct list_head pending_lpi_list;
     } vgic;
 
     /* Timer registers  */
diff --git a/xen/include/asm-arm/gic-its.h b/xen/include/asm-arm/gic-its.h
index 4e9841a..1f881c0 100644
--- a/xen/include/asm-arm/gic-its.h
+++ b/xen/include/asm-arm/gic-its.h
@@ -136,6 +136,12 @@ int gicv3_lpi_allocate_host_lpi(struct host_its *its,
 int gicv3_lpi_drop_host_lpi(struct host_its *its,
                             uint32_t devid, uint32_t eventid,
                             uint32_t host_lpi);
+
+static inline int gicv3_lpi_get_priority(struct domain *d, uint32_t lpi)
+{
+    return GIC_PRI_IRQ;
+}
+
 #else
 
 static inline void gicv3_its_dt_init(const struct dt_device_node *node)
@@ -175,6 +181,10 @@ static inline int gicv3_lpi_drop_host_lpi(struct host_its *its,
 {
     return 0;
 }
+static inline int gicv3_lpi_get_priority(struct domain *d, uint32_t lpi)
+{
+    return GIC_PRI_IRQ;
+}
 
 #endif /* CONFIG_HAS_ITS */
 
diff --git a/xen/include/asm-arm/vgic.h b/xen/include/asm-arm/vgic.h
index 300f461..4e29ba6 100644
--- a/xen/include/asm-arm/vgic.h
+++ b/xen/include/asm-arm/vgic.h
@@ -83,6 +83,12 @@ struct pending_irq
     struct list_head lr_queue;
 };
 
+struct lpi_pending_irq
+{
+    struct list_head entry;
+    struct pending_irq pirq;
+};
+
 #define NR_INTERRUPT_PER_RANK   32
 #define INTERRUPT_RANK_MASK (NR_INTERRUPT_PER_RANK - 1)
 
@@ -296,8 +302,11 @@ extern struct vcpu *vgic_get_target_vcpu(struct vcpu *v, unsigned int virq);
 extern void vgic_vcpu_inject_irq(struct vcpu *v, unsigned int virq);
 extern void vgic_vcpu_inject_spi(struct domain *d, unsigned int virq);
 extern void vgic_clear_pending_irqs(struct vcpu *v);
+extern void vgic_init_pending_irq(struct pending_irq *p, unsigned int virq);
 extern struct pending_irq *irq_to_pending(struct vcpu *v, unsigned int irq);
 extern struct pending_irq *spi_to_pending(struct domain *d, unsigned int irq);
+extern struct pending_irq *lpi_to_pending(struct vcpu *v, unsigned int irq,
+                                          bool allocate);
 extern struct vgic_irq_rank *vgic_rank_offset(struct vcpu *v, int b, int n, int s);
 extern struct vgic_irq_rank *vgic_rank_irq(struct vcpu *v, unsigned int irq);
 extern int vgic_emulate(struct cpu_user_regs *regs, union hsr hsr);
-- 
2.9.0


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