1 files changed, 9 insertions, 0 deletions

diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c
index 9a5963e07a82..b8ad14bb1170 100644
--- a/arch/powerpc/mm/book3s64/hash_utils.c
+++ b/arch/powerpc/mm/book3s64/hash_utils.c
@@ -1899,11 +1899,20 @@ void hash__setup_initial_memory_limit(phys_addr_t first_memblock_base,
          *
          * For guests on platforms before POWER9, we clamp the it limit to 1G
          * to avoid some funky things such as RTAS bugs etc...
+         *
+         * On POWER9 we limit to 1TB in case the host erroneously told us that
+         * the RMA was >1TB. Effective address bits 0:23 are treated as zero
+         * (meaning the access is aliased to zero i.e. addr = addr % 1TB)
+         * for virtual real mode addressing and so it doesn't make sense to
+         * have an area larger than 1TB as it can't be addressed.
          */
         if (!early_cpu_has_feature(CPU_FTR_HVMODE)) {
                 ppc64_rma_size = first_memblock_size;
                 if (!early_cpu_has_feature(CPU_FTR_ARCH_300))
                         ppc64_rma_size = min_t(u64, ppc64_rma_size, 0x40000000);
+                else
+                        ppc64_rma_size = min_t(u64, ppc64_rma_size,
+                                               1UL << SID_SHIFT_1T);
 
                 /* Finally limit subsequent allocations */
                 memblock_set_current_limit(ppc64_rma_size);