[PATCH v2] 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 (nG, SH, AP, NS, ATTR) which do not exist in the table descriptor format.

Set PT_PT to 0x403:
 - Bit 0 (P): Valid bit (required)
 - Bit 1 (T): Table descriptor type (required)
 - Bit 10 (AF): Access flag (future-proof for FEAT_HAFT)

Hardware ignores bits [11:2] but setting AF prepares for ARMv9's FEAT_HAFT. 
Using 0x403 rather than minimal 0x3 provides forward compatibility while 
avoiding unnecessary reserved bits.

This updates both arm32 and arm64 for consistency.

Signed-off-by: Gabriel Quintáns Souto <gabi.qs.mail@xxxxxxxxx>

---
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 5032e6c075..cab7be0621 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     0xf7f /* nG=1 AF=1 SH=11 AP=01 NS=1 ATTR=111 T=1 P=1 */
+#define PT_PT     0x403 /* AF=1 T=1 P=1 (bits [11:2] ignored in table 
descriptors) */
 #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 c3cb262e88..375d703d9b 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     0x743 /* AF=1 RES=11 SKL=1 IGN=0000 T=1 P=1 */
+#define PT_PT     0x403 /* AF=1 T=1 P=1 (bits [11:2] ignored in table 
descriptors) */
 #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