powerpc/mm: Enable radix GTSE only if supported.

Make GTSE an MMU feature and enable it by default for radix.
However for guest, conditionally enable it if hypervisor supports
it via OV5 vector. Let prom_init ask for radix GTSE only if the
support exists.

Having GTSE as an MMU feature will make it easy to enable radix
without GTSE. Currently radix assumes GTSE is enabled by default.
Signed-off-by: Bharata B Rao <bharata@linux.ibm.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200703053608.12884-2-bharata@linux.ibm.com

arch/powerpc/include/asm/mmu.h

@@ -28,6 +28,9 @@
  * Individual features below.
  */
 
+/* Guest Translation Shootdown Enable */
+#define MMU_FTR_GTSE			ASM_CONST(0x00001000)
+
 /*
  * Support for 68 bit VA space. We added that from ISA 2.05
  */
@@ -173,6 +176,7 @@ enum {
 #endif
 #ifdef CONFIG_PPC_RADIX_MMU
 		MMU_FTR_TYPE_RADIX |
+		MMU_FTR_GTSE |
 #ifdef CONFIG_PPC_KUAP
 		MMU_FTR_RADIX_KUAP |
 #endif /* CONFIG_PPC_KUAP */

arch/powerpc/kernel/dt_cpu_ftrs.c

@@ -336,6 +336,7 @@ static int __init feat_enable_mmu_radix(struct dt_cpu_feature *f)
 #ifdef CONFIG_PPC_RADIX_MMU
 	cur_cpu_spec->mmu_features |= MMU_FTR_TYPE_RADIX;
 	cur_cpu_spec->mmu_features |= MMU_FTRS_HASH_BASE;
+	cur_cpu_spec->mmu_features |= MMU_FTR_GTSE;
 	cur_cpu_spec->cpu_user_features |= PPC_FEATURE_HAS_MMU;
 
 	return 1;

arch/powerpc/kernel/prom_init.c

@@ -1336,12 +1336,15 @@ static void __init prom_check_platform_support(void)
 		}
 	}
 
-	if (supported.radix_mmu && supported.radix_gtse &&
-	    IS_ENABLED(CONFIG_PPC_RADIX_MMU)) {
-		/* Radix preferred - but we require GTSE for now */
-		prom_debug("Asking for radix with GTSE\n");
+	if (supported.radix_mmu && IS_ENABLED(CONFIG_PPC_RADIX_MMU)) {
+		/* Radix preferred - Check if GTSE is also supported */
+		prom_debug("Asking for radix\n");
 		ibm_architecture_vec.vec5.mmu = OV5_FEAT(OV5_MMU_RADIX);
-		ibm_architecture_vec.vec5.radix_ext = OV5_FEAT(OV5_RADIX_GTSE);
+		if (supported.radix_gtse)
+			ibm_architecture_vec.vec5.radix_ext =
+					OV5_FEAT(OV5_RADIX_GTSE);
+		else
+			prom_debug("Radix GTSE isn't supported\n");
 	} else if (supported.hash_mmu) {
 		/* Default to hash mmu (if we can) */
 		prom_debug("Asking for hash\n");

arch/powerpc/mm/init_64.c

@@ -407,12 +407,15 @@ static void __init early_check_vec5(void)
 		if (!(vec5[OV5_INDX(OV5_RADIX_GTSE)] &
 						OV5_FEAT(OV5_RADIX_GTSE))) {
 			pr_warn("WARNING: Hypervisor doesn't support RADIX with GTSE\n");
-		}
+			cur_cpu_spec->mmu_features &= ~MMU_FTR_GTSE;
+		} else
+			cur_cpu_spec->mmu_features |= MMU_FTR_GTSE;
 		/* Do radix anyway - the hypervisor said we had to */
 		cur_cpu_spec->mmu_features |= MMU_FTR_TYPE_RADIX;
 	} else if (mmu_supported == OV5_FEAT(OV5_MMU_HASH)) {
 		/* Hypervisor only supports hash - disable radix */
 		cur_cpu_spec->mmu_features &= ~MMU_FTR_TYPE_RADIX;
+		cur_cpu_spec->mmu_features &= ~MMU_FTR_GTSE;
 	}
 }