[xen staging] xen/arm: mpu: Enable MPU

[patchbot@xxxxxxx]

commit 5423a08eae391e781a457fa2b819431ab36f85bd
Author:     Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>
AuthorDate: Mon Nov 18 12:12:49 2024 +0000
Commit:     Julien Grall <jgrall@xxxxxxxxxx>
CommitDate: Mon Dec 2 18:28:54 2024 +0000

    xen/arm: mpu: Enable MPU
    
    After the regions have been created, now we enable the MPU. For this we 
disable
    the background region so that the new memory map created for the regions 
take
    effect. Also, we treat all RW regions as non executable and the data cache 
is
    enabled.
    
    Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>
    Reviewed-by: Luca Fancellu <luca.fancellu@xxxxxxx>
    Acked-by: Julien Grall <jgrall@xxxxxxxxxx>
---
 xen/arch/arm/arm64/mpu/head.S | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/xen/arch/arm/arm64/mpu/head.S b/xen/arch/arm/arm64/mpu/head.S
index a06589566f..bacf8315f9 100644
--- a/xen/arch/arm/arm64/mpu/head.S
+++ b/xen/arch/arm/arm64/mpu/head.S
@@ -5,6 +5,9 @@
 
 #include <asm/arm64/mpu.h>
 
+/* Backgroud region enable/disable */
+#define SCTLR_ELx_BR    BIT(17, UL)
+
 #define REGION_TEXT_PRBAR       0x38    /* SH=11 AP=10 XN=00 */
 #define REGION_RO_PRBAR         0x3A    /* SH=11 AP=10 XN=10 */
 #define REGION_DATA_PRBAR       0x32    /* SH=11 AP=00 XN=10 */
@@ -75,6 +78,29 @@ FUNC_LOCAL(fail_insufficient_regions)
     b   1b
 END(fail_insufficient_regions)
 
+/*
+ * Enable EL2 MPU and data cache
+ * If the Background region is enabled, then the MPU uses the default memory
+ * map as the Background region for generating the memory
+ * attributes when MPU is disabled.
+ * Since the default memory map of the Armv8-R AArch64 architecture is
+ * IMPLEMENTATION DEFINED, we intend to turn off the Background region here.
+ *
+ * Clobbers x0
+ *
+ */
+FUNC_LOCAL(enable_mpu)
+    mrs   x0, SCTLR_EL2
+    bic   x0, x0, #SCTLR_ELx_BR       /* Disable Background region */
+    orr   x0, x0, #SCTLR_Axx_ELx_M    /* Enable MPU */
+    orr   x0, x0, #SCTLR_Axx_ELx_C    /* Enable D-cache */
+    orr   x0, x0, #SCTLR_Axx_ELx_WXN  /* Enable WXN */
+    msr   SCTLR_EL2, x0
+    isb
+
+    ret
+END(enable_mpu)
+
 /*
  * Maps the various sections of Xen (described in xen.lds.S) as different MPU
  * regions.
@@ -114,6 +140,7 @@ FUNC(enable_boot_cpu_mm)
     ldr   x2, =__bss_end
     prepare_xen_region x0, x1, x2, x3, x4, x5
 
+    b    enable_mpu
     ret
 END(enable_boot_cpu_mm)
 
--
generated by git-patchbot for /home/xen/git/xen.git#staging