arm64/sysreg: Allow a 'Mapping' descriptor for system registers

*EL02 and *_EL12 system registers are actually only accessors for
EL0 and EL1 registers accessed from EL2 when HCR_EL2.E2H==1. They
do not have fields of their own.

To that effect, introduce a 'Mapping' entry, describing which
system register an _EL12 register maps to.

Implementation wise, this is handled the same was as Fields,
which ls only a comment.

Acked-by: Mark Rutland <[email protected]>
Reviewed-by: Mark Brown <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

Author: Marc Zyngier

arch/arm64/tools/gen-sysreg.awk

@@ -206,7 +206,7 @@ END {
 
 # Currently this is effectivey a comment, in future we may want to emit
 # defines for the fields.
-/^Fields/ && block_current() == "Sysreg" {
+(/^Fields/ || /^Mapping/) && block_current() == "Sysreg" {
 	expect_fields(2)
 
 	if (next_bit != 63)

arch/arm64/tools/sysreg

@@ -24,8 +24,16 @@
 #	...
 # EndEnum
 
-# Alternatively if multiple registers share the same layout then
-# a SysregFields block can be used to describe the shared layout
+# For VHE aliases (*_EL12, *_EL02) of system registers, a Mapping
+# entry describes the register the alias actually accesses:
+
+# Sysreg 	<name_EL12>	<op0> 	<op1>	<crn>	<crm>	<op2>
+# Mapping	<name_EL1>
+# EndSysreg
+
+# Where multiple system regsiters are not VHE aliases but share a
+# common layout, a SysregFields block can be used to describe the
+# shared layout:
 
 # SysregFields	<fieldsname>
 # <field>