KVM: Fix GSI number space limit

KVM tells us the number of GSIs it can handle inside the kernel. That value is
basically KVM_MAX_IRQ_ROUTES. However when we try to set the GSI mapping table,
it checks for

    r = -EINVAL;
    if (routing.nr >= KVM_MAX_IRQ_ROUTES)
        goto out;

erroring out even when we're only using all of the GSIs. To make sure we never
hit that limit, let's reduce the number of GSIs we get from KVM by one.

Cc: qemu-stable@nongnu.org
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 00008418aa22700f6c49e794e79f53aeb157d10f)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/kvm-all.c b/kvm-all.c
index 9f18ea38b9e15718ad27d87d44e44f92c01736a2..7e05f08c2e978c2c4488dff98160b9043c6f4a50 100644 (file)
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -965,7 +965,7 @@ void kvm_init_irq_routing(KVMState *s)
 {
     int gsi_count, i;
 
-    gsi_count = kvm_check_extension(s, KVM_CAP_IRQ_ROUTING);
+    gsi_count = kvm_check_extension(s, KVM_CAP_IRQ_ROUTING) - 1;
     if (gsi_count > 0) {
         unsigned int gsi_bits, i;