arm64: Make the PHYS_MASK_SHIFT dynamic

Make the PHYS_MASK_SHIFT dynamic for Realms. This is only is required
for masking the PFN from a pte entry. Elsewhere, we could still use the
PA bits configured by the kernel. So, this patch:

 -> renames PHYS_MASK_SHIFT -> MAX_PHYS_SHIFT as supported by the kernel
 -> Makes PHYS_MASK_SHIFT -> Dynamic value of the (I)PA bit width
 -> For a realm: reduces phys_mask_shift if the RMM reports a smaller
    configured size for the guest.

Co-developed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>

arch/arm64/include/asm/kvm_arm.h

@@ -346,7 +346,7 @@
  * bits in PAR are res0.
  */
 #define PAR_TO_HPFAR(par)		\
-	(((par) & GENMASK_ULL(52 - 1, 12)) >> 8)
+	(((par) & GENMASK_ULL(MAX_PHYS_MASK_SHIFT - 1, 12)) >> 8)
 
 #define ECN(x) { ESR_ELx_EC_##x, #x }
 

arch/arm64/include/asm/pgtable-hwdef.h

@@ -178,8 +178,8 @@
 /*
  * Highest possible physical address supported.
  */
-#define PHYS_MASK_SHIFT		(CONFIG_ARM64_PA_BITS)
-#define PHYS_MASK		((UL(1) << PHYS_MASK_SHIFT) - 1)
+#define MAX_PHYS_MASK_SHIFT	(CONFIG_ARM64_PA_BITS)
+#define MAX_PHYS_MASK		((UL(1) << PHYS_MASK_SHIFT) - 1)
 
 #define TTBR_CNP_BIT		(UL(1) << 0)
 

arch/arm64/include/asm/pgtable.h

@@ -35,6 +35,11 @@
 #include <linux/sched.h>
 #include <linux/page_table_check.h>
 
+extern unsigned int phys_mask_shift;
+
+#define PHYS_MASK_SHIFT		(phys_mask_shift)
+#define PHYS_MASK		((1UL << PHYS_MASK_SHIFT) - 1)
+
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 #define __HAVE_ARCH_FLUSH_PMD_TLB_RANGE
 

arch/arm64/kernel/head.S

@@ -371,7 +371,7 @@ SYM_FUNC_START_LOCAL(create_idmap)
 #error "Mismatch between VA_BITS and page size/number of translation levels"
 #endif
 #else
-#define IDMAP_PGD_ORDER	(PHYS_MASK_SHIFT - PGDIR_SHIFT)
+#define IDMAP_PGD_ORDER	(MAX_PHYS_MASK_SHIFT - PGDIR_SHIFT)
 #define EXTRA_SHIFT
 	/*
 	 * If VA_BITS == 48, we don't have to configure an additional

arch/arm64/kernel/rsi.c

@@ -12,6 +12,8 @@ struct realm_config __attribute((aligned(PAGE_SIZE))) config;
 unsigned long prot_ns_shared;
 EXPORT_SYMBOL(prot_ns_shared);
 
+unsigned int phys_mask_shift = CONFIG_ARM64_PA_BITS;
+
 DEFINE_STATIC_KEY_FALSE_RO(rsi_present);
 
 static bool rsi_version_matches(void)
@@ -54,5 +56,8 @@ void __init arm64_rsi_init(void)
 		return;
 	prot_ns_shared = BIT(config.ipa_bits - 1);
 
+	if (config.ipa_bits - 1 < phys_mask_shift)
+		phys_mask_shift = config.ipa_bits - 1;
+
 	static_branch_enable(&rsi_present);
 }