KVM: arm64: Allow guests with >48-bit IPA size on FEAT_LPA2 systems

With all the page-table infrastructure in place, we can finally increase
the maximum permisable IPA size to 52-bits on 4KB and 16KB page systems
that have FEAT_LPA2.
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20231127111737.1897081-11-ryan.roberts@arm.com

arch/arm64/kvm/reset.c

@@ -280,12 +280,11 @@ int __init kvm_set_ipa_limit(void)
 	parange = cpuid_feature_extract_unsigned_field(mmfr0,
 				ID_AA64MMFR0_EL1_PARANGE_SHIFT);
 	/*
-	 * IPA size beyond 48 bits could not be supported
-	 * on either 4K or 16K page size. Hence let's cap
-	 * it to 48 bits, in case it's reported as larger
-	 * on the system.
+	 * IPA size beyond 48 bits for 4K and 16K page size is only supported
+	 * when LPA2 is available. So if we have LPA2, enable it, else cap to 48
+	 * bits, in case it's reported as larger on the system.
 	 */
-	if (PAGE_SIZE != SZ_64K)
+	if (!kvm_lpa2_is_enabled() && PAGE_SIZE != SZ_64K)
 		parange = min(parange, (unsigned int)ID_AA64MMFR0_EL1_PARANGE_48);
 
 	/*