arm: Modify type of actlr to register_t

AArch64 registers are 64bit whereas AArch32 registers
are 32bit or 64bit. MSR/MRS are expecting 64bit values thus
we should get rid of helpers READ/WRITE_SYSREG32
in favour of using READ/WRITE_SYSREG.
We should also use register_t type when reading sysregs
which can correspond to uint64_t or uint32_t.
Even though many AArch64 registers have upper 32bit reserved
it does not mean that they can't be widen in the future.

ACTLR_EL1 system register bits are implementation defined
which means it is possibly a latent bug on current HW as the CPU
implementer may already have decided to use the top 32bit.

Signed-off-by: Michal Orzel <michal.orzel@arm.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>

xen/arch/arm/domain.c

@@ -330,7 +330,7 @@ static void schedule_tail(struct vcpu *prev)
 
 static void continue_new_vcpu(struct vcpu *prev)
 {
-    current->arch.actlr = READ_SYSREG32(ACTLR_EL1);
+    current->arch.actlr = READ_SYSREG(ACTLR_EL1);
     processor_vcpu_initialise(current);
 
     schedule_tail(prev);

xen/include/asm-arm/domain.h

@@ -156,7 +156,7 @@ struct arch_vcpu
 
     /* Control Registers */
     register_t sctlr;
-    uint32_t actlr;
+    register_t actlr;
     uint32_t cpacr;
 
     uint32_t contextidr;