VT-d: use qword MMIO access for MSI address writes

Also make dmar_{read,write}q() actually do what their names suggest (we
don#t need to be concerned of 32-bit restrictions anymore).

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -1054,8 +1054,7 @@ static void dma_msi_set_affinity(struct 
 
     spin_lock_irqsave(&iommu->register_lock, flags);
     dmar_writel(iommu->reg, DMAR_FEDATA_REG, msg.data);
-    dmar_writel(iommu->reg, DMAR_FEADDR_REG, msg.address_lo);
-    dmar_writel(iommu->reg, DMAR_FEUADDR_REG, msg.address_hi);
+    dmar_writeq(iommu->reg, DMAR_FEADDR_REG, msg.address);
     spin_unlock_irqrestore(&iommu->register_lock, flags);
 }
 
--- a/xen/drivers/passthrough/vtd/iommu.h
+++ b/xen/drivers/passthrough/vtd/iommu.h
@@ -51,17 +51,10 @@
 #define    DMAR_IRTA_REG   0xB8    /* intr remap */
 
 #define OFFSET_STRIDE        (9)
-#define dmar_readl(dmar, reg) readl(dmar + reg)
-#define dmar_writel(dmar, reg, val) writel(val, dmar + reg)
-#define dmar_readq(dmar, reg) ({ \
-        u32 lo, hi; \
-        lo = dmar_readl(dmar, reg); \
-        hi = dmar_readl(dmar, reg + 4); \
-        (((u64) hi) << 32) + lo; })
-#define dmar_writeq(dmar, reg, val) do {\
-        dmar_writel(dmar, reg, (u32)val); \
-        dmar_writel(dmar, reg + 4, (u32)((u64) val >> 32)); \
-    } while (0)
+#define dmar_readl(dmar, reg) readl((dmar) + (reg))
+#define dmar_readq(dmar, reg) readq((dmar) + (reg))
+#define dmar_writel(dmar, reg, val) writel(val, (dmar) + (reg))
+#define dmar_writeq(dmar, reg, val) writeq(val, (dmar) + (reg))
 
 #define VER_MAJOR(v)        (((v) & 0xf0) >> 4)
 #define VER_MINOR(v)        ((v) & 0x0f)