[PATCH v3 1/6] arm64: head.S: Initialise MPAM EL2 registers and disable traps

[James Morse]

Add code to head.S's el2_setup to detect MPAM and disable any EL2 traps.
This register resets to an unknown value, setting it to the default
parititons/pmg before we enable the MMU is the best thing to do.

Kexec/kdump will depend on this if the previous kernel left the CPU
configured with a restrictive configuration.

If linux is booted at the highest implemented exception level el2_setup
will clear the enable bit, disabling MPAM.

This code can't be enabled until a subsequent patch adds the Kconfig
and cpufeature boiler plate.

Signed-off-by: James Morse <james.morse at arm.com>
---
 arch/arm64/include/asm/el2_setup.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h
index b7afaa026842..1e2181820a0a 100644
--- a/arch/arm64/include/asm/el2_setup.h
+++ b/arch/arm64/include/asm/el2_setup.h
@@ -208,6 +208,21 @@
 	msr	spsr_el2, x0
 .endm
 
+.macro __init_el2_mpam
+#ifdef CONFIG_ARM64_MPAM
+	/* Memory Partioning And Monitoring: disable EL2 traps */
+	mrs	x1, id_aa64pfr0_el1
+	ubfx	x0, x1, #ID_AA64PFR0_EL1_MPAM_SHIFT, #4
+	cbz	x0, .Lskip_mpam_\@		// skip if no MPAM
+	msr_s	SYS_MPAM2_EL2, xzr		// use the default partition
+						// and disable lower traps
+	mrs_s	x0, SYS_MPAMIDR_EL1
+	tbz	x0, #17, .Lskip_mpam_\@		// skip if no MPAMHCR reg
+	msr_s	SYS_MPAMHCR_EL2, xzr		// clear TRAP_MPAMIDR_EL1 -> EL2
+.Lskip_mpam_\@:
+#endif /* CONFIG_ARM64_MPAM */
+.endm
+
 /**
  * Initialize EL2 registers to sane values. This should be called early on all
  * cores that were booted in EL2. Note that everything gets initialised as
@@ -225,6 +240,7 @@
 	__init_el2_stage2
 	__init_el2_gicv3
 	__init_el2_hstr
+	__init_el2_mpam
 	__init_el2_nvhe_idregs
 	__init_el2_cptr
 	__init_el2_fgt
-- 
2.39.2