diff --git a/docs/porting-guide.md b/docs/porting-guide.md
index 8a024d8..e967b0e 100644
--- a/docs/porting-guide.md
+++ b/docs/porting-guide.md
@@ -631,8 +631,10 @@
 the `bl31_args` structure pointed to by `bl2_to_bl31_args`.
 
 Platform security components are configured if required. For the Base FVP the
-TZC-400 TrustZone controller is configured to grant secure and non-secure access
-to DRAM.
+TZC-400 TrustZone controller is configured to only grant non-secure access
+to DRAM. This avoids aliasing between secure and non-secure accesses in the
+TLB and cache - secure execution states can use the NS attributes in the
+MMU translation tables to access the DRAM.
 
 This function is also responsible for initializing the storage abstraction layer
 which is used to load further bootloader images.
diff --git a/plat/fvp/plat_security.c b/plat/fvp/plat_security.c
index 32306cd..c39907a 100644
--- a/plat/fvp/plat_security.c
+++ b/plat/fvp/plat_security.c
@@ -88,36 +88,33 @@
 	tzc_disable_filters(&controller);
 
 	/*
-	 * Allow full access to all DRAM to supported devices for the
-	 * moment. Give access to the CPUs and Virtio. Some devices
+	 * Allow only non-secure access to all DRAM to supported devices.
+	 * Give access to the CPUs and Virtio. Some devices
 	 * would normally use the default ID so allow that too. We use
-	 * three different regions to cover the three separate blocks of
-	 * memory in the FVPs. We allow secure access to DRAM to load NS
-	 * software.
-	 * FIXME: In current models Virtio uses a reserved ID. This is
-	 * not correct and will be fixed.
+	 * two regions to cover the blocks of physical memory in the FVPs.
+	 *
+	 * Software executing in the secure state, such as a secure
+	 * boot-loader, can access the DRAM by using the NS attributes in
+	 * the MMU translation tables and descriptors.
 	 */
 
-	/* Set to cover 2GB block of DRAM */
+	/* Set to cover the first block of DRAM */
 	tzc_configure_region(&controller, FILTER_SHIFT(0), 1,
-			DRAM_BASE, 0xFFFFFFFF, TZC_REGION_S_RDWR,
-			TZC_REGION_ACCESS_RDWR(FVP_NSAID_AP) |
+			DRAM_BASE, 0xFFFFFFFF, TZC_REGION_S_NONE,
 			TZC_REGION_ACCESS_RDWR(FVP_NSAID_DEFAULT) |
-			TZC_REGION_ACCESS_RDWR(FVP_NSAID_RES5));
+			TZC_REGION_ACCESS_RDWR(FVP_NSAID_PCI) |
+			TZC_REGION_ACCESS_RDWR(FVP_NSAID_AP) |
+			TZC_REGION_ACCESS_RDWR(FVP_NSAID_VIRTIO) |
+			TZC_REGION_ACCESS_RDWR(FVP_NSAID_VIRTIO_OLD));
 
-	/* Set to cover the 30GB block */
+	/* Set to cover the second block of DRAM */
 	tzc_configure_region(&controller, FILTER_SHIFT(0), 2,
-			0x880000000, 0xFFFFFFFFF, TZC_REGION_S_RDWR,
-			TZC_REGION_ACCESS_RDWR(FVP_NSAID_AP) |
+			0x880000000, 0xFFFFFFFFF, TZC_REGION_S_NONE,
 			TZC_REGION_ACCESS_RDWR(FVP_NSAID_DEFAULT) |
-			TZC_REGION_ACCESS_RDWR(FVP_NSAID_RES5));
-
-	/* Set to cover 480GB block */
-	tzc_configure_region(&controller, FILTER_SHIFT(0), 3,
-			0x8800000000, 0xFFFFFFFFFF, TZC_REGION_S_RDWR,
+			TZC_REGION_ACCESS_RDWR(FVP_NSAID_PCI) |
 			TZC_REGION_ACCESS_RDWR(FVP_NSAID_AP) |
-			TZC_REGION_ACCESS_RDWR(FVP_NSAID_DEFAULT) |
-			TZC_REGION_ACCESS_RDWR(FVP_NSAID_RES5));
+			TZC_REGION_ACCESS_RDWR(FVP_NSAID_VIRTIO) |
+			TZC_REGION_ACCESS_RDWR(FVP_NSAID_VIRTIO_OLD));
 
 	/*
 	 * TODO: Interrupts are not currently supported. The only
diff --git a/plat/fvp/platform.h b/plat/fvp/platform.h
index 3fe892e..6c28a14 100644
--- a/plat/fvp/platform.h
+++ b/plat/fvp/platform.h
@@ -307,18 +307,21 @@
 
 /*
  * The NSAIDs for this platform as used to program the TZC400.
- * TODO:
- * This list and the numbers in it is still changing on the Base FVP.
- * For now only specify the NSAIDs we actually use.
  */
 
 /* The FVP has 4 bits of NSAIDs. Used with TZC FAIL_ID (ACE Lite ID width) */
 #define FVP_AID_WIDTH			4
+
+/* NSAIDs used by devices in TZC filter 0 on FVP */
 #define FVP_NSAID_DEFAULT		0
+#define FVP_NSAID_PCI			1
+#define FVP_NSAID_VIRTIO		8  /* from FVP v5.6 onwards */
 #define FVP_NSAID_AP			9  /* Application Processors */
+#define FVP_NSAID_VIRTIO_OLD		15 /* until FVP v5.5 */
 
-/* FIXME: Currently incorrectly used by Virtio */
-#define FVP_NSAID_RES5			15
+/* NSAIDs used by devices in TZC filter 2 on FVP */
+#define FVP_NSAID_HDLCD0		2
+#define FVP_NSAID_CLCD			7
 
 
 /*******************************************************************************