[PATCH v4 4/6] MIPS: kexec: Do not flush system wide caches in machine_kexec()

[Dengcheng Zhu <dzhu@wavecomp.com>]

Instead of __flush_cache_all(), simply flush local icache range. In systems
without IOCU, flushing system wide caches require sending IPIs. But other
CPUs have disabled local IRQs waiting for the reboot signal. It will then
cause system hang.

This patch fixes this problem.

Tested-by: Rachel Mozes <rachel.mozes@intel.com>
Reported-by: Rachel Mozes <rachel.mozes@intel.com>
Signed-off-by: Dengcheng Zhu <dzhu@wavecomp.com>
---
 arch/mips/kernel/machine_kexec.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/mips/kernel/machine_kexec.c b/arch/mips/kernel/machine_kexec.c
index baffc7113204..c2119e448490 100644
--- a/arch/mips/kernel/machine_kexec.c
+++ b/arch/mips/kernel/machine_kexec.c
@@ -139,7 +139,16 @@ machine_kexec(struct kimage *image)
 
 	printk("Will call new kernel at %08lx\n", image->start);
 	printk("Bye ...\n");
-	__flush_cache_all();
+	/*
+	 * __flush_cache_all() is expensive but unnecessary. More
+	 * importantly, it could freeze the system as it may need to send
+	 * IPIs, whereas other CPUs have been waiting for the reboot signal
+	 * (kexec_ready_to_reboot) with local irqs disabled, because
+	 * machine_crash_shutdown() has been called prior to entering
+	 * this function - machine_kexec().
+	 */
+	local_flush_icache_range(reboot_code_buffer,
+				 reboot_code_buffer + relocate_new_kernel_size);
 #ifdef CONFIG_SMP
 	atomic_set(&kexec_ready_to_reboot, 1);
 
-- 
2.17.1