MIPS: traps: Make sure secondary cores have a sane ebase register

We shouldn't trust that the secondary cores will have a sane ebase register
(either from the bootloader or during the hardware design phase) so use the
ebase address as calculated by the boot CPU.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Cc: Maciej W. Rozycki <macro@linux-mips.org>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Petri Gynther <pgynther@google.com>
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12328/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/traps.c

@@ -2116,6 +2116,13 @@ void per_cpu_trap_init(bool is_boot_cpu)
 	 *  o read IntCtl.IPFDC to determine the fast debug channel interrupt
 	 */
 	if (cpu_has_mips_r2_r6) {
+		/*
+		 * We shouldn't trust a secondary core has a sane EBASE register
+		 * so use the one calculated by the boot CPU.
+		 */
+		if (!is_boot_cpu)
+			write_c0_ebase(ebase);
+
 		cp0_compare_irq_shift = CAUSEB_TI - CAUSEB_IP;
 		cp0_compare_irq = (read_c0_intctl() >> INTCTLB_IPTI) & 7;
 		cp0_perfcount_irq = (read_c0_intctl() >> INTCTLB_IPPCI) & 7;