intc/arm_gic: Add virtualization extensions helper macros and functions

Add some helper macros and functions related to the virtualization
extensions to gic_internal.h.

The GICH_LR_* macros help extracting specific fields of a list register
value. The only tricky one is the priority field as only the MSB are
stored. The value must be shifted accordingly to obtain the correct
priority value.

gic_is_vcpu() and gic_get_vcpu_real_id() help with (v)CPU id manipulation
to abstract the fact that vCPU id are in the range
[ GIC_NCPU; (GIC_NCPU + num_cpu) [.

gic_lr_* and gic_virq_is_valid() help with the list registers.
gic_get_lr_entry() returns the LR entry for a given (vCPU, irq) pair. It
is meant to be used in contexts where we know for sure that the entry
exists, so we assert that entry is actually found, and the caller can
avoid the NULL check on the returned pointer.

Signed-off-by: Luc Michel <luc.michel@greensocs.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20180727095421.386-8-luc.michel@greensocs.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/intc/arm_gic.c

@@ -61,6 +61,11 @@ static inline int gic_get_current_cpu(GICState *s)
     return 0;
 }
 
+static inline int gic_get_current_vcpu(GICState *s)
+{
+    return gic_get_current_cpu(s) + GIC_NCPU;
+}
+
 /* Return true if this GIC config has interrupt groups, which is
  * true if we're a GICv2, or a GICv1 with the security extensions.
  */

hw/intc/gic_internal.h

@@ -129,6 +129,20 @@ REG32(GICH_LR63, 0x1fc)
      R_GICH_LR0_Priority_MASK | R_GICH_LR0_State_MASK | \
      R_GICH_LR0_Grp1_MASK | R_GICH_LR0_HW_MASK)
 
+#define GICH_LR_STATE_INVALID         0
+#define GICH_LR_STATE_PENDING         1
+#define GICH_LR_STATE_ACTIVE          2
+#define GICH_LR_STATE_ACTIVE_PENDING  3
+
+#define GICH_LR_VIRT_ID(entry) (FIELD_EX32(entry, GICH_LR0, VirtualID))
+#define GICH_LR_PHYS_ID(entry) (FIELD_EX32(entry, GICH_LR0, PhysicalID))
+#define GICH_LR_CPUID(entry) (FIELD_EX32(entry, GICH_LR0, CPUID))
+#define GICH_LR_EOI(entry) (FIELD_EX32(entry, GICH_LR0, EOI))
+#define GICH_LR_PRIORITY(entry) (FIELD_EX32(entry, GICH_LR0, Priority) << 3)
+#define GICH_LR_STATE(entry) (FIELD_EX32(entry, GICH_LR0, State))
+#define GICH_LR_GROUP(entry) (FIELD_EX32(entry, GICH_LR0, Grp1))
+#define GICH_LR_HW(entry) (FIELD_EX32(entry, GICH_LR0, HW))
+
 /* Valid bits for GICC_CTLR for GICv1, v1 with security extensions,
  * GICv2 and GICv2 with security extensions:
  */
@@ -164,4 +178,64 @@ static inline bool gic_is_vcpu(int cpu)
     return cpu >= GIC_NCPU;
 }
 
+static inline int gic_get_vcpu_real_id(int cpu)
+{
+    return (cpu >= GIC_NCPU) ? (cpu - GIC_NCPU) : cpu;
+}
+
+/* Return true if the given vIRQ state exists in a LR and is either active or
+ * pending and active.
+ *
+ * This function is used to check that a guest's `end of interrupt' or
+ * `interrupts deactivation' request is valid, and matches with a LR of an
+ * already acknowledged vIRQ (i.e. has the active bit set in its state).
+ */
+static inline bool gic_virq_is_valid(GICState *s, int irq, int vcpu)
+{
+    int cpu = gic_get_vcpu_real_id(vcpu);
+    int lr_idx;
+
+    for (lr_idx = 0; lr_idx < s->num_lrs; lr_idx++) {
+        uint32_t *entry = &s->h_lr[lr_idx][cpu];
+
+        if ((GICH_LR_VIRT_ID(*entry) == irq) &&
+            (GICH_LR_STATE(*entry) & GICH_LR_STATE_ACTIVE)) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+/* Return a pointer on the LR entry matching the given vIRQ.
+ *
+ * This function is used to retrieve an LR for which we know for sure that the
+ * corresponding vIRQ exists in the current context (i.e. its current state is
+ * not `invalid'):
+ *   - Either the corresponding vIRQ has been validated with gic_virq_is_valid()
+ *     so it is `active' or `active and pending',
+ *   - Or it was pending and has been selected by gic_get_best_virq(). It is now
+ *     `pending', `active' or `active and pending', depending on what the guest
+ *     already did with this vIRQ.
+ *
+ * Having multiple LRs with the same VirtualID leads to UNPREDICTABLE
+ * behaviour in the GIC. We choose to return the first one that matches.
+ */
+static inline uint32_t *gic_get_lr_entry(GICState *s, int irq, int vcpu)
+{
+    int cpu = gic_get_vcpu_real_id(vcpu);
+    int lr_idx;
+
+    for (lr_idx = 0; lr_idx < s->num_lrs; lr_idx++) {
+        uint32_t *entry = &s->h_lr[lr_idx][cpu];
+
+        if ((GICH_LR_VIRT_ID(*entry) == irq) &&
+            (GICH_LR_STATE(*entry) != GICH_LR_STATE_INVALID)) {
+            return entry;
+        }
+    }
+
+    g_assert_not_reached();
+}
+
 #endif /* QEMU_ARM_GIC_INTERNAL_H */