[Qemu-devel] [PATCH 17/38] ivshmem: Clean up MSI-X conditions

[Markus Armbruster <armbru@redhat.com>]

There are three predicates related to MSI-X:

* ivshmem_has_feature(s, IVSHMEM_MSI) is true unless the non-MSI-X
  variant of the device is selected with msi=off.

* msix_present() is true when the device has the PCI capability MSI-X.
  It's initially false, and becomes true during successful realize of
  the MSI-X variant of the device.  Thus, it's the same as
  ivshmem_has_feature(s, IVSHMEM_MSI) for realized devices.

* msix_enabled() is true when msix_present() is true and guest software
  has enabled MSI-X.

Code that differs between the non-MSI-X and the MSI-X variant of the
device needs to be guarded by ivshmem_has_feature(s, IVSHMEM_MSI) or
by msix_present(), except the latter works only for realized devices.

Code that depends on whether MSI-X is in use needs to be guarded with
msix_enabled().

Code review led me to two minor messes:

* ivshmem_vector_notify() calls msix_notify() even when
  !msix_enabled(), unlike most other MSI-X-capable devices.  As far as
  I can tell, msix_notify() does nothing when !msix_enabled().  Add
  the guard anyway.

* Most callers of ivshmem_use_msix() guard it with
  ivshmem_has_feature(s, IVSHMEM_MSI).  Not necessary, because
  ivshmem_use_msix() does nothing when !msix_present().  That's
  ivshmem's only use of msix_present(), though.  Rename
  ivshmem_use_msix() to ivshmem_vector_use(), replace msix_present()
  by ivshmem_has_feature() there, and drop the redundant guards.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 hw/misc/ivshmem.c | 22 +++++++++-------------
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
index 7191914..cfea151 100644
--- a/hw/misc/ivshmem.c
+++ b/hw/misc/ivshmem.c
@@ -274,7 +274,9 @@ static void ivshmem_vector_notify(void *opaque)
 
     IVSHMEM_DPRINTF("interrupt on vector %p %d\n", pdev, vector);
     if (ivshmem_has_feature(s, IVSHMEM_MSI)) {
-        msix_notify(pdev, vector);
+        if (msix_enabled(pdev)) {
+            msix_notify(pdev, vector);
+        }
     } else {
         ivshmem_IntrStatus_write(s, 1);
     }
@@ -712,13 +714,12 @@ static void ivshmem_check_version(void *opaque, const uint8_t * buf, int size)
 /* Select the MSI-X vectors used by device.
  * ivshmem maps events to vectors statically, so
  * we just enable all vectors on init and after reset. */
-static void ivshmem_use_msix(IVShmemState * s)
+static void ivshmem_vector_use(IVShmemState *s)
 {
     PCIDevice *d = PCI_DEVICE(s);
     int i;
 
-    IVSHMEM_DPRINTF("%s, msix present: %d\n", __func__, msix_present(d));
-    if (!msix_present(d)) {
+    if (!ivshmem_has_feature(s, IVSHMEM_MSI)) {
         return;
     }
 
@@ -733,7 +734,7 @@ static void ivshmem_reset(DeviceState *d)
 
     s->intrstatus = 0;
     s->intrmask = 0;
-    ivshmem_use_msix(s);
+    ivshmem_vector_use(s);
 }
 
 static int ivshmem_setup_interrupts(IVShmemState *s)
@@ -747,9 +748,9 @@ static int ivshmem_setup_interrupts(IVShmemState *s)
         }
 
         IVSHMEM_DPRINTF("msix initialized (%d vectors)\n", s->vectors);
-        ivshmem_use_msix(s);
     }
 
+    ivshmem_vector_use(s);
     return 0;
 }
 
@@ -1034,12 +1035,7 @@ static int ivshmem_pre_load(void *opaque)
 
 static int ivshmem_post_load(void *opaque, int version_id)
 {
-    IVShmemState *s = opaque;
-
-    if (ivshmem_has_feature(s, IVSHMEM_MSI)) {
-        ivshmem_use_msix(s);
-    }
-
+    ivshmem_vector_use(opaque);
     return 0;
 }
 
@@ -1067,11 +1063,11 @@ static int ivshmem_load_old(QEMUFile *f, void *opaque, int version_id)
 
     if (ivshmem_has_feature(s, IVSHMEM_MSI)) {
         msix_load(pdev, f);
-        ivshmem_use_msix(s);
     } else {
         s->intrstatus = qemu_get_be32(f);
         s->intrmask = qemu_get_be32(f);
     }
+    ivshmem_vector_use(s);
 
     return 0;
 }
-- 
2.4.3