arm64: setup: name 'tcr2' register

TCR2_EL1 introduced some additional controls besides TCR_EL1. Currently
only PIE is supported and enabled by writing TCR2_EL1 directly if PIE
detected.

Introduce a named register 'tcr2' just like 'tcr' we've already had.
It'll be initialized to 0 and updated if certain feature detected and
needs to be enabled. Touch the TCR2_EL1 registers at last with the
updated 'tcr2' value if FEAT_TCR2 supported by checking
ID_AA64MMFR3_EL1.TCRX. Then we can extend the support of other features
controlled by TCR2_EL1.

Reviewed-by: Catalin Marinas <[email protected]>
Signed-off-by: Yicong Yang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Catalin Marinas <[email protected]>

Author: Yicong Yang

arch/arm64/mm/proc.S

@@ -465,10 +465,12 @@ SYM_FUNC_START(__cpu_setup)
 	 */
 	mair	.req	x17
 	tcr	.req	x16
+	tcr2	.req	x15
 	mov_q	mair, MAIR_EL1_SET
 	mov_q	tcr, TCR_T0SZ(IDMAP_VA_BITS) | TCR_T1SZ(VA_BITS_MIN) | TCR_CACHE_FLAGS | \
 		     TCR_SHARED | TCR_TG_FLAGS | TCR_KASLR_FLAGS | TCR_ASID16 | \
 		     TCR_TBI0 | TCR_A1 | TCR_KASAN_SW_FLAGS | TCR_MTE_FLAGS
+	mov	tcr2, xzr
 
 	tcr_clear_errata_bits tcr, x9, x5
 
@@ -525,11 +527,16 @@ alternative_else_nop_endif
 #undef PTE_MAYBE_NG
 #undef PTE_MAYBE_SHARED
 
-	mov	x0, TCR2_EL1x_PIE
-	msr	REG_TCR2_EL1, x0
+	orr	tcr2, tcr2, TCR2_EL1x_PIE
 
 .Lskip_indirection:
 
+	mrs_s	x1, SYS_ID_AA64MMFR3_EL1
+	ubfx	x1, x1, #ID_AA64MMFR3_EL1_TCRX_SHIFT, #4
+	cbz	x1, 1f
+	msr	REG_TCR2_EL1, tcr2
+1:
+
 	/*
 	 * Prepare SCTLR
 	 */
@@ -538,4 +545,5 @@ alternative_else_nop_endif
 
 	.unreq	mair
 	.unreq	tcr
+	.unreq	tcr2
 SYM_FUNC_END(__cpu_setup)