armv8: Ensure EL1&0 VMSA is enabled

On Armv8-R, the EL1&0 memory system architecture is configurable as a
VMSA or PMSA, and resets to an "architecturally unknown" value.

Add code to armv8_switch_to_el1_m which detects whether the MSA at
EL1&0 is configurable using the id_aa64mmfr0_el1 register MSA fields.
If it is we must ensure the VMSA is enabled so that a rich OS can boot.

The MSA and MSA_FRAC fields are described in the Armv8-R architecture
profile supplement (section G1.3.7):
https://developer.arm.com/documentation/ddi0600/latest/Signed-off-by: NPeter Hoyes <Peter.Hoyes@arm.com>

arch/arm/include/asm/macro.h

@@ -316,6 +316,23 @@ lr	.req	x30
 	csel	\tmp, \tmp2, \tmp, eq
 	msr	hcr_el2, \tmp
 
+	/*
+	 * Detect whether the system has a configurable memory system
+	 * architecture at EL1&0
+	 */
+	mrs	\tmp, id_aa64mmfr0_el1
+	lsr	\tmp, \tmp, #48
+	and	\tmp, \tmp, #((ID_AA64MMFR0_EL1_MSA_MASK | \
+			ID_AA64MMFR0_EL1_MSA_FRAC_MASK) >> 48)
+	cmp	\tmp, #((ID_AA64MMFR0_EL1_MSA_USE_FRAC | \
+			ID_AA64MMFR0_EL1_MSA_FRAC_VMSA) >> 48)
+	bne	2f
+
+	/* Ensure the EL1&0 VMSA is enabled */
+	mov	\tmp, #(VTCR_EL2_MSA)
+	msr	vtcr_el2, \tmp
+2:
+
 	/* Return to the EL1_SP1 mode from EL2 */
 	ldr	\tmp, =(SPSR_EL_DEBUG_MASK | SPSR_EL_SERR_MASK |\
 			SPSR_EL_IRQ_MASK | SPSR_EL_FIQ_MASK |\

arch/arm/include/asm/system.h

@@ -83,6 +83,30 @@
 #define HCR_EL2_RW_AARCH32	(0 << 31) /* Lower levels are AArch32         */
 #define HCR_EL2_HCD_DIS		(1 << 29) /* Hypervisor Call disabled         */
 
+/*
+ * VTCR_EL2 bits definitions
+ */
+#define VTCR_EL2_MSA      	(1 << 31) /* EL1&0 memory architecture        */
+
+/*
+ * ID_AA64MMFR0_EL1 bits definitions
+ */
+#define ID_AA64MMFR0_EL1_MSA_FRAC_MASK		(0xFUL << 52) /* Memory system
+								 architecture
+								 frac         */
+#define ID_AA64MMFR0_EL1_MSA_FRAC_VMSA		(0x2UL << 52) /* EL1&0 supports
+								 VMSA         */
+#define ID_AA64MMFR0_EL1_MSA_FRAC_PMSA		(0x1UL << 52) /* EL1&0 only
+							         supports PMSA*/
+#define ID_AA64MMFR0_EL1_MSA_FRAC_NO_PMSA	(0x0UL << 52) /* No PMSA
+								 support      */
+#define ID_AA64MMFR0_EL1_MSA_MASK		(0xFUL << 48) /* Memory system
+								 architecture */
+#define ID_AA64MMFR0_EL1_MSA_USE_FRAC		(0xFUL << 48) /* Use MSA_FRAC */
+#define ID_AA64MMFR0_EL1_MSA_VMSA		(0x0UL << 48) /* Memory system
+								 architecture
+								 is VMSA      */
+
 /*
  * ID_AA64ISAR1_EL1 bits definitions
  */