[Qemu-devel] [PATCH 04/11] vfio-pci: Rework MSIX setup/teardown

[Alex Williamson <alex.williamson@redhat.com>]

We try to do lazy initialization of MSIX since we don't actually need
to setup anything until MSIX vectors start getting used.  This leads
to problems if MSIX is enabled, but never used (we can end up trying
to re-enable INTx while it's still enabled).  We also run into
problems trying to expand our reset function to tear down interrupts
as we can then get vector release notifications after we've released
data structures.  By making explicit initialization and teardown we
can avoid both of these problems and behave more similar to bare
metal.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---

 hw/vfio_pci.c |  108 +++++++++++++++++++++++++++++----------------------------
 1 file changed, 55 insertions(+), 53 deletions(-)

diff --git a/hw/vfio_pci.c b/hw/vfio_pci.c
index 7413f2d..89e00ba 100644
--- a/hw/vfio_pci.c
+++ b/hw/vfio_pci.c
@@ -72,8 +72,6 @@ static void vfio_disable_irqindex(VFIODevice *vdev, int index)
     };
 
     ioctl(vdev->fd, VFIO_DEVICE_SET_IRQS, &irq_set);
-
-    vdev->interrupt = VFIO_INT_NONE;
 }
 
 /*
@@ -278,10 +276,6 @@ static int vfio_enable_vectors(VFIODevice *vdev, bool msix)
 
     g_free(irq_set);
 
-    if (!ret) {
-        vdev->interrupt = msix ? VFIO_INT_MSIX : VFIO_INT_MSI;
-    }
-
     return ret;
 }
 
@@ -296,15 +290,6 @@ static int vfio_msix_vector_use(PCIDevice *pdev,
             vdev->host.domain, vdev->host.bus, vdev->host.slot,
             vdev->host.function, nr);
 
-    if (vdev->interrupt != VFIO_INT_MSIX) {
-        vfio_disable_interrupts(vdev);
-    }
-
-    if (!vdev->msi_vectors) {
-        vdev->msi_vectors = g_malloc0(vdev->msix->entries *
-                                      sizeof(VFIOMSIVector));
-    }
-
     vector = &vdev->msi_vectors[nr];
     vector->vdev = vdev;
     vector->use = true;
@@ -457,6 +442,23 @@ static void msi_set_qsize(PCIDevice *pdev, uint8_t size)
     pci_set_word(config + PCI_MSI_FLAGS, flags);
 }
 
+static void vfio_enable_msix(VFIODevice *vdev)
+{
+    vfio_disable_interrupts(vdev);
+
+    vdev->msi_vectors = g_malloc0(vdev->msix->entries * sizeof(VFIOMSIVector));
+
+    vdev->interrupt = VFIO_INT_MSIX;
+
+    if (msix_set_vector_notifiers(&vdev->pdev, vfio_msix_vector_use,
+                                  vfio_msix_vector_release)) {
+        error_report("vfio: msix_set_vector_notifiers failed\n");
+    }
+
+    DPRINTF("%s(%04x:%02x:%02x.%x)\n", __func__, vdev->host.domain,
+            vdev->host.bus, vdev->host.slot, vdev->host.function);
+}
+
 static void vfio_enable_msi(VFIODevice *vdev)
 {
     int ret, i;
@@ -529,17 +531,43 @@ retry:
 
     msi_set_qsize(&vdev->pdev, vdev->nr_vectors);
 
+    vdev->interrupt = VFIO_INT_MSI;
+
     DPRINTF("%s(%04x:%02x:%02x.%x) Enabled %d MSI vectors\n", __func__,
             vdev->host.domain, vdev->host.bus, vdev->host.slot,
             vdev->host.function, vdev->nr_vectors);
 }
 
-static void vfio_disable_msi_x(VFIODevice *vdev, bool msix)
+static void vfio_disable_msi_common(VFIODevice *vdev)
+{
+    g_free(vdev->msi_vectors);
+    vdev->msi_vectors = NULL;
+    vdev->nr_vectors = 0;
+    vdev->interrupt = VFIO_INT_NONE;
+
+    vfio_enable_intx(vdev);
+}
+
+static void vfio_disable_msix(VFIODevice *vdev)
+{
+    msix_unset_vector_notifiers(&vdev->pdev);
+
+    if (vdev->nr_vectors) {
+        vfio_disable_irqindex(vdev, VFIO_PCI_MSIX_IRQ_INDEX);
+    }
+
+    vfio_disable_msi_common(vdev);
+
+    DPRINTF("%s(%04x:%02x:%02x.%x, msi%s)\n", __func__,
+            vdev->host.domain, vdev->host.bus, vdev->host.slot,
+            vdev->host.function, msix ? "x" : "");
+}
+
+static void vfio_disable_msi(VFIODevice *vdev)
 {
     int i;
 
-    vfio_disable_irqindex(vdev, msix ? VFIO_PCI_MSIX_IRQ_INDEX :
-                                       VFIO_PCI_MSI_IRQ_INDEX);
+    vfio_disable_irqindex(vdev, VFIO_PCI_MSI_IRQ_INDEX);
 
     for (i = 0; i < vdev->nr_vectors; i++) {
         VFIOMSIVector *vector = &vdev->msi_vectors[i];
@@ -558,26 +586,15 @@ static void vfio_disable_msi_x(VFIODevice *vdev, bool msix)
                                 NULL, NULL, NULL);
         }
 
-        if (msix) {
-            msix_vector_unuse(&vdev->pdev, i);
-        }
-
         event_notifier_cleanup(&vector->interrupt);
     }
 
-    g_free(vdev->msi_vectors);
-    vdev->msi_vectors = NULL;
-    vdev->nr_vectors = 0;
-
-    if (!msix) {
-        msi_set_qsize(&vdev->pdev, 0); /* Actually still means 1 vector */
-    }
+    vfio_disable_msi_common(vdev);
 
-    DPRINTF("%s(%04x:%02x:%02x.%x, msi%s)\n", __func__,
-            vdev->host.domain, vdev->host.bus, vdev->host.slot,
-            vdev->host.function, msix ? "x" : "");
+    msi_set_qsize(&vdev->pdev, 0); /* Actually still means 1 vector */
 
-    vfio_enable_intx(vdev);
+    DPRINTF("%s(%04x:%02x:%02x.%x)\n", __func__, vdev->host.domain,
+            vdev->host.bus, vdev->host.slot, vdev->host.function);
 }
 
 /*
@@ -763,7 +780,7 @@ static void vfio_pci_write_config(PCIDevice *pdev, uint32_t addr,
         if (!was_enabled && is_enabled) {
             vfio_enable_msi(vdev);
         } else if (was_enabled && !is_enabled) {
-            vfio_disable_msi_x(vdev, false);
+            vfio_disable_msi(vdev);
         }
     }
 
@@ -776,9 +793,9 @@ static void vfio_pci_write_config(PCIDevice *pdev, uint32_t addr,
         is_enabled = msix_enabled(pdev);
 
         if (!was_enabled && is_enabled) {
-            /* vfio_msix_vector_use handles this automatically */
+            vfio_enable_msix(vdev);
         } else if (was_enabled && !is_enabled) {
-            vfio_disable_msi_x(vdev, true);
+            vfio_disable_msix(vdev);
         }
     }
 }
@@ -973,10 +990,10 @@ static void vfio_disable_interrupts(VFIODevice *vdev)
         vfio_disable_intx(vdev);
         break;
     case VFIO_INT_MSI:
-        vfio_disable_msi_x(vdev, false);
+        vfio_disable_msi(vdev);
         break;
     case VFIO_INT_MSIX:
-        vfio_disable_msi_x(vdev, true);
+        vfio_disable_msix(vdev);
         break;
     }
 }
@@ -1094,15 +1111,6 @@ static int vfio_setup_msix(VFIODevice *vdev, int pos)
         return ret;
     }
 
-    ret = msix_set_vector_notifiers(&vdev->pdev, vfio_msix_vector_use,
-                                    vfio_msix_vector_release);
-    if (ret) {
-        error_report("vfio: msix_set_vector_notifiers failed %d\n", ret);
-        msix_uninit(&vdev->pdev, &vdev->bars[vdev->msix->table_bar].mem,
-                    &vdev->bars[vdev->msix->pba_bar].mem);
-        return ret;
-    }
-
     return 0;
 }
 
@@ -1111,12 +1119,6 @@ static void vfio_teardown_msi(VFIODevice *vdev)
     msi_uninit(&vdev->pdev);
 
     if (vdev->msix) {
-        /* FIXME: Why can't unset just silently do nothing?? */
-        if (vdev->pdev.msix_vector_use_notifier &&
-            vdev->pdev.msix_vector_release_notifier) {
-            msix_unset_vector_notifiers(&vdev->pdev);
-        }
-
         msix_uninit(&vdev->pdev, &vdev->bars[vdev->msix->table_bar].mem,
                     &vdev->bars[vdev->msix->pba_bar].mem);
     }