[PATCH v3 5/8] x86/iommu: make code addressing CVE-2011-1898 no VT-d specific

[Xenia Ragiadakou <burzalodowa@xxxxxxxxx>]

The variable untrusted_msi indicates whether the system is vulnerable to
CVE-2011-1898 due to the absence of interrupt remapping  support.
AMD iommus with interrupt remapping disabled are also exposed.
Therefore move the definition of the variable to the common x86 iommu code.

Also, since the current implementation assumes that only PV guests are prone
to this attack, take the opportunity to define untrusted_msi only when PV is
enabled.

No functional change intended.

Signed-off-by: Xenia Ragiadakou <burzalodowa@xxxxxxxxx>
---

Changes in v3:
  - change untrusted_msi from being VT-d specific to PV specific and
    update commit log accordingly
  - remove unnecessary #ifdef guard from its declaration

 xen/drivers/passthrough/vtd/iommu.c | 3 ---
 xen/drivers/passthrough/x86/iommu.c | 5 +++++
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/xen/drivers/passthrough/vtd/iommu.c 
b/xen/drivers/passthrough/vtd/iommu.c
index 62e143125d..dae2426cb9 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -54,9 +54,6 @@
                                  ? dom_iommu(d)->arch.vtd.pgd_maddr \
                                  : (pdev)->arch.vtd.pgd_maddr)
 
-/* Possible unfiltered LAPIC/MSI messages from untrusted sources? */
-bool __read_mostly untrusted_msi;
-
 bool __read_mostly iommu_igfx = true;
 bool __read_mostly iommu_qinval = true;
 #ifndef iommu_snoop
diff --git a/xen/drivers/passthrough/x86/iommu.c 
b/xen/drivers/passthrough/x86/iommu.c
index f671b0f2bb..c5021ea023 100644
--- a/xen/drivers/passthrough/x86/iommu.c
+++ b/xen/drivers/passthrough/x86/iommu.c
@@ -36,6 +36,11 @@ bool __initdata iommu_superpages = true;
 
 enum iommu_intremap __read_mostly iommu_intremap = iommu_intremap_full;
 
+#ifdef CONFIG_PV
+/* Possible unfiltered LAPIC/MSI messages from untrusted sources? */
+bool __read_mostly untrusted_msi;
+#endif
+
 #ifndef iommu_intpost
 /*
  * In the current implementation of VT-d posted interrupts, in some extreme
-- 
2.37.2