powerpc/mm/hash: Compute the segment size correctly for ISA 3.0

PowerISA 3.0 encodes the segment size in the second half of hash page
table entry. Update hpte_decode() accordingly.

Fixes: 50de596de8be ("powerpc/mm/hash: Add support for Power9 Hash")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/hash_native_64.c

@@ -550,7 +550,11 @@ static void hpte_decode(struct hash_pte *hpte, unsigned long slot,
 		}
 	}
 	/* This works for all page sizes, and for 256M and 1T segments */
-	*ssize = hpte_v >> HPTE_V_SSIZE_SHIFT;
+	if (cpu_has_feature(CPU_FTR_ARCH_300))
+		*ssize = hpte_r >> HPTE_R_3_0_SSIZE_SHIFT;
+	else
+		*ssize = hpte_v >> HPTE_V_SSIZE_SHIFT;
+
 	shift = mmu_psize_defs[size].shift;
 
 	avpn = (HPTE_V_AVPN_VAL(hpte_v) & ~mmu_psize_defs[size].avpnm);