FROMGIT: arm64: head.S: Initialise MPAM EL2 registers and disable traps

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.

Signed-off-by: James Morse <james.morse@arm.com>

Bug: 221768437
(cherry picked from commit fa0ff38f06b397d8a92d88eb8083c2c5a20ac87f
 git://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git mpam/snapshot/v5.16)
Change-Id: I2758f7f7b236d09a207e13d1165efb6887e8611a
Signed-off-by: Valentin Schneider <Valentin.Schneider@arm.com>
[bm: amended commit msg, dropped config option and switched to named labels]
Signed-off-by: Beata Michalska <beata.michalska@arm.com>

arch/arm64/include/asm/el2_setup.h

@@ -149,6 +149,20 @@
 	msr	spsr_el2, x0
 .endm
 
+.macro __init_el2_mpam
+	/* Memory Partioning And Monitoring: disable EL2 traps */
+	mrs	x1, id_aa64pfr0_el1
+	ubfx	x0, x1, #ID_AA64PFR0_MPAM_SHIFT, #4
+	cbz	x0, .Lskip_mpam_\@		// skip if no MPAM
+	msr_s	SYS_MPAM0_EL1, xzr		// use the default partition..
+	msr_s	SYS_MPAM2_EL2, xzr		// ..and disable lower traps
+	msr_s	SYS_MPAM1_EL1, xzr
+	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_\@:
+.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
@@ -165,6 +179,7 @@
 	__init_el2_stage2
 	__init_el2_gicv3
 	__init_el2_hstr
+	__init_el2_mpam
 	__init_el2_nvhe_idregs
 	__init_el2_nvhe_cptr
 	__init_el2_nvhe_sve