irq: inform device of IRQ mask & unmask via callback (#694)

Client masks or unmasks a device IRQ using the
VFIO_USER_DEVICE_SET_IRQS message. Inform the device of such changes to
the IRQ state.

Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
Reviewed-by: John Levon <john.levon@nutanix.com>

3 files changed, 44 insertions, 2 deletions

diff --git a/lib/irq.c b/lib/irq.c
index c7820aa..eadad7b 100644
--- a/lib/irq.c
+++ b/lib/irq.c
@@ -154,6 +154,32 @@ irqs_reset(vfu_ctx_t *vfu_ctx)
     }
 }
 
+static void
+irqs_set_state(vfu_ctx_t *vfu_ctx, struct vfio_irq_set *irq_set)
+{
+    vfu_dev_irq_state_cb_t *cb = NULL;
+    uint32_t irq_action;
+    bool mask = false;
+
+    assert(irq_set->index < VFU_DEV_NUM_IRQS);
+    cb = vfu_ctx->irq_state_cbs[irq_set->index];
+    if (cb == NULL) {
+        return;
+    }
+
+    assert((irq_set->start + irq_set->count) <=
+            vfu_ctx->irq_count[irq_set->index]);
+
+    irq_action = irq_set->flags & VFIO_IRQ_SET_ACTION_TYPE_MASK;
+
+    assert((irq_action & VFIO_IRQ_SET_ACTION_MASK) ||
+           (irq_action & VFIO_IRQ_SET_ACTION_UNMASK));
+
+    mask = (irq_action & VFIO_IRQ_SET_ACTION_MASK) ? true : false;
+
+    cb(vfu_ctx, irq_set->start, irq_set->count, mask);
+}
+
 static int
 irqs_set_data_none(vfu_ctx_t *vfu_ctx, struct vfio_irq_set *irq_set)
 {
@@ -345,8 +371,7 @@ handle_device_set_irqs(vfu_ctx_t *vfu_ctx, vfu_msg_t *msg)
     switch (irq_set->flags & VFIO_IRQ_SET_ACTION_TYPE_MASK) {
     case VFIO_IRQ_SET_ACTION_MASK:
     case VFIO_IRQ_SET_ACTION_UNMASK:
-        // We're always edge-triggered without un/mask support.
-        // FIXME: return an error? We don't report MASKABLE
+        irqs_set_state(vfu_ctx, irq_set);
         return 0;
     case VFIO_IRQ_SET_ACTION_TRIGGER:
         break;
diff --git a/lib/libvfio-user.c b/lib/libvfio-user.c
index 47e3572..c45ceeb 100644
--- a/lib/libvfio-user.c
+++ b/lib/libvfio-user.c
@@ -1968,6 +1968,22 @@ vfu_setup_device_nr_irqs(vfu_ctx_t *vfu_ctx, enum vfu_dev_irq_type type,
 }
 
 EXPORT int
+vfu_setup_irq_state_callback(vfu_ctx_t *vfu_ctx, enum vfu_dev_irq_type type,
+                             vfu_dev_irq_state_cb_t *cb)
+{
+    assert(vfu_ctx != NULL);
+
+    if (type >= VFU_DEV_NUM_IRQS) {
+        vfu_log(vfu_ctx, LOG_ERR, "Invalid IRQ type index %u", type);
+        return ERROR_INT(EINVAL);
+    }
+
+    vfu_ctx->irq_state_cbs[type] = cb;
+
+    return 0;
+}
+
+EXPORT int
 vfu_setup_device_migration_callbacks(vfu_ctx_t *vfu_ctx,
                                      const vfu_migration_callbacks_t *callbacks,
                                      uint64_t data_offset)
diff --git a/lib/private.h b/lib/private.h
index 4c483f2..7ffd6be 100644
--- a/lib/private.h
+++ b/lib/private.h
@@ -172,6 +172,7 @@ struct vfu_ctx {
     struct migration        *migration;
 
     uint32_t                irq_count[VFU_DEV_NUM_IRQS];
+    vfu_dev_irq_state_cb_t  *irq_state_cbs[VFU_DEV_NUM_IRQS];
     vfu_irqs_t              *irqs;
     bool                    realized;
     vfu_dev_type_t          dev_type;