[PATCH v3] arm: Fix PT_PT table descriptor value and comment

[Gabriel Quintáns Souto <gabi.qs.mail@xxxxxxxxx>]

Per ARMv7-A/ARMv8-A ARM, bits [11:2] of table descriptors are
ignored by hardware. The original comment incorrectly described
block/page descriptor fields which are not present in table
descriptors.

Use the minimal valid encoding for table descriptors by setting
PT_PT to 0x3.

This updates both arm32 and arm64 for consistency.

Signed-off-by: Gabriel Quintáns Souto <gabi.qs.mail@xxxxxxxxx>
---
Changes in v3:
- Use 0x3 instead of 0x403

Changes in v2:
- Apply fix to both arm32 and arm64
- Use 0x403 instead of 0x743
---
 xen/arch/arm/arm32/mmu/head.S | 2 +-
 xen/arch/arm/arm64/mmu/head.S | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/arm32/mmu/head.S b/xen/arch/arm/arm32/mmu/head.S
index cab7be0621..3731322f7e 100644
--- a/xen/arch/arm/arm32/mmu/head.S
+++ b/xen/arch/arm/arm32/mmu/head.S
@@ -8,7 +8,7 @@
 #include <asm/page.h>
 #include <asm/early_printk.h>
 
-#define PT_PT     0x403 /* AF=1 T=1 P=1 (bits [11:2] ignored in table 
descriptors) */
+#define PT_PT     0x3   /* T=1 P=1 */
 #define PT_MEM    0xf7d /* nG=1 AF=1 SH=11 AP=01 NS=1 ATTR=111 T=0 P=1 */
 #define PT_MEM_L3 0xf7f /* nG=1 AF=1 SH=11 AP=01 NS=1 ATTR=111 T=1 P=1 */
 #define PT_DEV    0xe71 /* nG=1 AF=1 SH=10 AP=01 NS=1 ATTR=100 T=0 P=1 */
diff --git a/xen/arch/arm/arm64/mmu/head.S b/xen/arch/arm/arm64/mmu/head.S
index 375d703d9b..8e514d2114 100644
--- a/xen/arch/arm/arm64/mmu/head.S
+++ b/xen/arch/arm/arm64/mmu/head.S
@@ -8,7 +8,7 @@
 #include <asm/page.h>
 #include <asm/early_printk.h>
 
-#define PT_PT     0x403 /* AF=1 T=1 P=1 (bits [11:2] ignored in table 
descriptors) */
+#define PT_PT     0x3   /* T=1 P=1 */
 #define PT_MEM    0xf7d /* nG=1 AF=1 SH=11 AP=01 NS=1 ATTR=111 T=0 P=1 */
 #define PT_MEM_L3 0xf7f /* nG=1 AF=1 SH=11 AP=01 NS=1 ATTR=111 T=1 P=1 */
 #define PT_DEV    0xe71 /* nG=1 AF=1 SH=10 AP=01 NS=1 ATTR=100 T=0 P=1 */
-- 
2.54.0