[PATCH] x86/vMsi-x: check whether the msixtbl_list has been initialized or not when accessing it

[Chao Gao <chao.gao@intel.com>]

MSI-x tables' initialization had been detered in the commit
74c6dc2d0ac4dcab0c6243cdf6ed550c1532b798. If an assigned device does not support
MSI-x, the msixtbl_list won't be initialized. Howerver, both of following paths
    XEN_DOMCTL_bind_pt_irq
        pt_irq_create_bind
            msixtbl_pt_register
and
    XEN_DOMCTL_unbind_pt_irq
        pt_irq_destroy_bind
            msixtbl_pt_unregister
do not check this case and will cause Xen panic consequently.

Signed-off-by: Chao Gao <chao.gao@intel.com>
---
 xen/arch/x86/hvm/vmsi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/hvm/vmsi.c b/xen/arch/x86/hvm/vmsi.c
index e418b98..e0d710b 100644
--- a/xen/arch/x86/hvm/vmsi.c
+++ b/xen/arch/x86/hvm/vmsi.c
@@ -449,7 +449,7 @@ int msixtbl_pt_register(struct domain *d, struct pirq *pirq, uint64_t gtable)
     ASSERT(pcidevs_locked());
     ASSERT(spin_is_locked(&d->event_lock));
 
-    if ( !has_vlapic(d) )
+    if ( !has_vlapic(d) || !d->arch.hvm_domain.msixtbl_list.next )
         return -ENODEV;
 
     /*
@@ -519,7 +519,7 @@ void msixtbl_pt_unregister(struct domain *d, struct pirq *pirq)
     ASSERT(pcidevs_locked());
     ASSERT(spin_is_locked(&d->event_lock));
 
-    if ( !has_vlapic(d) )
+    if ( !has_vlapic(d) || !d->arch.hvm_domain.msixtbl_list.next )
         return;
 
     irq_desc = pirq_spin_lock_irq_desc(pirq, NULL);
-- 
1.8.3.1


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