From dcab90d90935f990407c86b671a7f1ac285d106c Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Tue, 31 Jul 2018 12:09:03 +0100 Subject: [PATCH] arm64: kexec: Add comment to explain use of __flush_icache_range() Now that we understand the deadlock arising from flush_icache_range() on the kexec crash kernel path, add a comment to justify the use of __flush_icache_range() here. Reported-by: Dave Kleikamp Signed-off-by: Will Deacon --- arch/arm64/kernel/machine_kexec.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c index 4c0eb30bfede..f6a5c6bc1434 100644 --- a/arch/arm64/kernel/machine_kexec.c +++ b/arch/arm64/kernel/machine_kexec.c @@ -184,8 +184,15 @@ void machine_kexec(struct kimage *kimage) /* Flush the reboot_code_buffer in preparation for its execution. */ __flush_dcache_area(reboot_code_buffer, arm64_relocate_new_kernel_size); + + /* + * Although we've killed off the secondary CPUs, we don't update + * the online mask if we're handling a crash kernel and consequently + * need to avoid flush_icache_range(), which will attempt to IPI + * the offline CPUs. Therefore, we must use the __* variant here. + */ __flush_icache_range((uintptr_t)reboot_code_buffer, - arm64_relocate_new_kernel_size); + arm64_relocate_new_kernel_size); /* Flush the kimage list and its buffers. */ kexec_list_flush(kimage);