powerpc/powernv: Remove real mode access limit for early allocations

This removes the RMA limit on powernv platform, which constrains
early allocations such as PACAs and stacks. There are still other
restrictions that must be followed, such as bolted SLB limits, but
real mode addressing has no constraints.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/hash_utils_64.c

@@ -1848,16 +1848,22 @@ void hash__setup_initial_memory_limit(phys_addr_t first_memblock_base,
 	 */
 	BUG_ON(first_memblock_base != 0);
 
-	/* On LPAR systems, the first entry is our RMA region,
-	 * non-LPAR 64-bit hash MMU systems don't have a limitation
-	 * on real mode access, but using the first entry works well
-	 * enough. We also clamp it to 1G to avoid some funky things
+	/*
+	 * On virtualized systems the first entry is our RMA region aka VRMA,
+	 * non-virtualized 64-bit hash MMU systems don't have a limitation
+	 * on real mode access.
+	 *
+	 * We also clamp it to 1G to avoid some funky things
 	 * such as RTAS bugs etc...
 	 */
-	ppc64_rma_size = min_t(u64, first_memblock_size, 0x40000000);
+	if (!early_cpu_has_feature(CPU_FTR_HVMODE)) {
+		ppc64_rma_size = min_t(u64, first_memblock_size, 0x40000000);
 
-	/* Finally limit subsequent allocations */
-	memblock_set_current_limit(ppc64_rma_size);
+		/* Finally limit subsequent allocations */
+		memblock_set_current_limit(ppc64_rma_size);
+	} else {
+		ppc64_rma_size = ULONG_MAX;
+	}
 }
 
 #ifdef CONFIG_DEBUG_FS

arch/powerpc/mm/pgtable-radix.c

@@ -628,22 +628,27 @@ void radix__setup_initial_memory_limit(phys_addr_t first_memblock_base,
 	 * physical on those processors
 	 */
 	BUG_ON(first_memblock_base != 0);
-	/*
-	 * We limit the allocation that depend on ppc64_rma_size
-	 * to first_memblock_size. We also clamp it to 1GB to
-	 * avoid some funky things such as RTAS bugs.
-	 *
-	 * On radix config we really don't have a limitation
-	 * on real mode access. But keeping it as above works
-	 * well enough.
-	 */
-	ppc64_rma_size = min_t(u64, first_memblock_size, 0x40000000);
-	/*
-	 * Finally limit subsequent allocations. We really don't want
-	 * to limit the memblock allocations to rma_size. FIXME!! should
-	 * we even limit at all ?
-	 */
-	memblock_set_current_limit(first_memblock_base + first_memblock_size);
+
+	if (!early_cpu_has_feature(CPU_FTR_HVMODE)) {
+		/*
+		 * We limit the allocation that depend on ppc64_rma_size
+		 * to first_memblock_size. We also clamp it to 1GB to
+		 * avoid some funky things such as RTAS bugs.
+		 *
+		 * On radix config we really don't have a limitation
+		 * on real mode access. But keeping it as above works
+		 * well enough.
+		 */
+		ppc64_rma_size = min_t(u64, first_memblock_size, 0x40000000);
+		/*
+		 * Finally limit subsequent allocations. We really don't want
+		 * to limit the memblock allocations to rma_size. FIXME!! should
+		 * we even limit at all ?
+		 */
+		memblock_set_current_limit(first_memblock_base + first_memblock_size);
+	} else {
+		ppc64_rma_size = ULONG_MAX;
+	}
 }
 
 #ifdef CONFIG_MEMORY_HOTPLUG