KVM: arm64: Work out supported block level at compile time

Work out the minimum page table level where KVM supports block mappings
at compile time. While at it, rewrite the comment around supported block
mappings to directly describe what KVM supports instead of phrasing in
terms of what it does not.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221007234151.461779-2-oliver.upton@linux.dev

Author: oupton

arch/arm64/include/asm/kvm_pgtable.h

@@ -13,6 +13,18 @@
 
 #define KVM_PGTABLE_MAX_LEVELS		4U
 
+/*
+ * The largest supported block sizes for KVM (no 52-bit PA support):
+ *  - 4K (level 1):	1GB
+ *  - 16K (level 2):	32MB
+ *  - 64K (level 2):	512MB
+ */
+#ifdef CONFIG_ARM64_4K_PAGES
+#define KVM_PGTABLE_MIN_BLOCK_LEVEL	1U
+#else
+#define KVM_PGTABLE_MIN_BLOCK_LEVEL	2U
+#endif
+
 static inline u64 kvm_get_parange(u64 mmfr0)
 {
 	u64 parange = cpuid_feature_extract_unsigned_field(mmfr0,
@@ -58,11 +70,7 @@ static inline u64 kvm_granule_size(u32 level)
 
 static inline bool kvm_level_supports_block_mapping(u32 level)
 {
-	/*
-	 * Reject invalid block mappings and don't bother with 4TB mappings for
-	 * 52-bit PAs.
-	 */
-	return !(level == 0 || (PAGE_SIZE != SZ_4K && level == 1));
+	return level >= KVM_PGTABLE_MIN_BLOCK_LEVEL;
 }
 
 /**