[PATCH v3 3/8] x86/iommu: snoop control is allowed only by Intel VT-d

[Xenia Ragiadakou <burzalodowa@xxxxxxxxx>]

The AMD-Vi driver forces coherent accesses by hardwiring the FC bit to 1.
Therefore, given that iommu_snoop is used only when the iommu is enabled,
when Xen is configured with only the AMD iommu enabled, iommu_snoop can be
reduced to a #define to true.

No functional change intended.

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

Changes in v3:
  - new patch
    This patch depends on Jan's patch "x86/shadow: sanitize iommu_snoop usage"
    to ensure that iommu_snoop is used only when the iommu is enabled

 xen/include/xen/iommu.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
index 4f22fc1bed..626731941b 100644
--- a/xen/include/xen/iommu.h
+++ b/xen/include/xen/iommu.h
@@ -74,7 +74,12 @@ extern enum __packed iommu_intremap {
    iommu_intremap_restricted,
    iommu_intremap_full,
 } iommu_intremap;
-extern bool iommu_igfx, iommu_qinval, iommu_snoop;
+extern bool iommu_igfx, iommu_qinval;
+#ifdef CONFIG_INTEL_IOMMU
+extern bool iommu_snoop;
+#else
+# define iommu_snoop true
+#endif /* CONFIG_INTEL_IOMMU */
 #else
 # define iommu_intremap false
 # define iommu_snoop false
-- 
2.37.2