[PATCH] kvm tools: Fix MSI-X table size set up

[Asias He]

We at most have VIRTIO_PCI_MAX_VQ entries for virt queue,
VIRTIO_PCI_MAX_CONFIG entries for config.

To quoto the PCI spec:

    System software reads this field to determine the
    MSI-X Table Size N, which is encoded as N-1.
    For example, a returned value of "00000000011"
    indicates a table size of 4.

So, we should set table size to

    VIRTIO_PCI_MAX_VQ + VIRTIO_PCI_MAX_CONFIG - 1

not

    VIRTIO_PCI_MAX_VQ + VIRTIO_PCI_MAX_CONFIG

Signed-off-by: Asias He <asias.he...@gmail.com>
---
 tools/kvm/include/kvm/virtio-pci.h |    5 +++--
 tools/kvm/virtio/pci.c             |   13 ++++++++++++-
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/tools/kvm/include/kvm/virtio-pci.h 
b/tools/kvm/include/kvm/virtio-pci.h
index d6d98df..81196e5 100644
--- a/tools/kvm/include/kvm/virtio-pci.h
+++ b/tools/kvm/include/kvm/virtio-pci.h
@@ -5,7 +5,8 @@
 
 #include <linux/types.h>
 
-#define VIRTIO_PCI_MAX_VQ 3
+#define VIRTIO_PCI_MAX_VQ      3
+#define VIRTIO_PCI_MAX_CONFIG  1
 
 struct kvm;
 
@@ -44,7 +45,7 @@ struct virtio_pci {
        u32                     msix_io_block;
        u32                     msix_pba_block;
        u64                     msix_pba;
-       struct msix_table       msix_table[VIRTIO_PCI_MAX_VQ + 1];
+       struct msix_table       msix_table[VIRTIO_PCI_MAX_VQ + 
VIRTIO_PCI_MAX_CONFIG];
 
        /* virtio queue */
        u16                     queue_selector;
diff --git a/tools/kvm/virtio/pci.c b/tools/kvm/virtio/pci.c
index fe3f746..17e570c 100644
--- a/tools/kvm/virtio/pci.c
+++ b/tools/kvm/virtio/pci.c
@@ -287,7 +287,18 @@ int virtio_pci__init(struct kvm *kvm, struct virtio_pci 
*vpci, void *dev,
 
        vpci->pci_hdr.msix.cap = PCI_CAP_ID_MSIX;
        vpci->pci_hdr.msix.next = 0;
-       vpci->pci_hdr.msix.ctrl = (VIRTIO_PCI_MAX_VQ + 1);
+       /*
+        * We at most have VIRTIO_PCI_MAX_VQ entries for virt queue,
+        * VIRTIO_PCI_MAX_CONFIG entries for config.
+        *
+        * To quoto the PCI spec:
+        *
+        * System software reads this field to determine the
+        * MSI-X Table Size N, which is encoded as N-1.
+        * For example, a returned value of "00000000011"
+        * indicates a table size of 4.
+        */
+       vpci->pci_hdr.msix.ctrl = (VIRTIO_PCI_MAX_VQ + VIRTIO_PCI_MAX_CONFIG - 
1);
 
        /*
         * Both table and PBA could be mapped on the same BAR, but for now
-- 
1.7.7.1

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