Blob Blame Raw
From fdad8c197b91f1010e4f61147f27513a4f061e40 Mon Sep 17 00:00:00 2001
From: Alex Williamson <alex.williamson@redhat.com>
Date: Mon, 12 Jan 2015 04:52:17 +0100
Subject: [PATCH 1/3] vfio-pci: Fix interrupt disabling

Message-id: <20150112045144.9215.59820.stgit@gimli.home>
Patchwork-id: 63242
O-Subject: [RHEL7.1 qemu-kvm PATCH] vfio-pci: Fix interrupt disabling
Bugzilla: 1180942
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
RH-Acked-by: Bandan Das <bsd@redhat.com>
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>

Upstream: b3e27c3aee8f5a96debfe0346e9c0e3a641a8516

When disabling MSI/X interrupts the disable functions will leave the
device in INTx mode (when available).  This matches how hardware
operates, INTx is enabled unless MSI/X is enabled (DisINTx is handled
separately).  Therefore when we really want to disable all interrupts,
such as when removing the device, and we start with the device in
MSI/X mode, we need to pass through INTx on our way to being
completely quiesced.

In well behaved situations, the guest driver will have shutdown the
device and it will start vfio_exitfn() in INTx mode, producing the
desired result.  If hot-unplug causes the guest to crash, we may get
the device in MSI/X state, which will leave QEMU with a bogus handler
installed.

Fix this by re-ordering our disable routine so that it should always
finish in VFIO_INT_NONE state, which is what all callers expect.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 hw/misc/vfio.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/hw/misc/vfio.c b/hw/misc/vfio.c
index abaa4c1..40b0923 100644
--- a/hw/misc/vfio.c
+++ b/hw/misc/vfio.c
@@ -2353,16 +2353,19 @@ static void vfio_listener_release(VFIOContainer *container)
  */
 static void vfio_disable_interrupts(VFIODevice *vdev)
 {
-    switch (vdev->interrupt) {
-    case VFIO_INT_INTx:
-        vfio_disable_intx(vdev);
-        break;
-    case VFIO_INT_MSI:
-        vfio_disable_msi(vdev);
-        break;
-    case VFIO_INT_MSIX:
+    /*
+     * More complicated than it looks.  Disabling MSI/X transitions the
+     * device to INTx mode (if supported).  Therefore we need to first
+     * disable MSI/X and then cleanup by disabling INTx.
+     */
+    if (vdev->interrupt == VFIO_INT_MSIX) {
         vfio_disable_msix(vdev);
-        break;
+    } else if (vdev->interrupt == VFIO_INT_MSI) {
+        vfio_disable_msi(vdev);
+    }
+
+    if (vdev->interrupt == VFIO_INT_INTx) {
+        vfio_disable_intx(vdev);
     }
 }
 
-- 
1.8.3.1