Re: [PATCH V3] MIPS: Loongson64: Add kexec/kdump support

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



在 2021/1/8 下午6:07, Jinyang He 写道:
Hi, Thomas,

On 01/08/2021 01:26 AM, Thomas Bogendoerfer wrote:
--- a/arch/mips/kernel/relocate_kernel.S
+++ b/arch/mips/kernel/relocate_kernel.S
@@ -6,6 +6,7 @@

   #include <asm/asm.h>
   #include <asm/asmmacro.h>
+#include <asm/cpu.h>
   #include <asm/regdef.h>
   #include <asm/mipsregs.h>
   #include <asm/stackframe.h>
@@ -133,6 +134,33 @@ LEAF(kexec_smp_wait)
   #else
       sync
   #endif
+
+#ifdef CONFIG_CPU_LOONGSON64
Is there a reason why you can't use the already existing infrastructure
the way cavium-octeon is doing it ? If you can't please explain why
so we can find a way to extend it. But having some sort of poking
loongson registers in generic MIPS code is a non starter.

Thomas.


Unlike the cavium-octeon platform, the Loongson64 platform needs some changes. Before the kernel starts, (before entering the kernel_entry), each CPU has its own state (the SMP system). For Loongson64, only the boot CPU will enter the kernel_entry, and other CPUs will query their mailbox value in a loop. This is what the BIOS does for the CPU. Here is different from cavium-octeon. All CPUs will enter the kernel_entry on cavium-octeon platform. Then the kernel_entry_setup, the co-CPUs will enter the query loop. I saw the kernel_entry_setup of other platforms, such as ip27, malta, and generic. They are not like cavium-octeon and the co-CPUs entering the loop may be earlier than entering kernel_entry. So I have reason to guess that most SMP system platform CPUs are similar to Loongson64.

Hi Jingyang,

As I commented before you may reuse play_dead logic in Loongson's smp.c.


relocate_kernel.S is like BIOS doing s omething for the CPU. It allows the boot CPU to start from the new kernel_entry and makes the co-CPUs enter a loop. The already existing infrastructure may be more suitable for non-smp platforms. Although we can do something with plat_smp_ops.kexec_nonboot_cpu, more new problems will arise in that case. The kexec process actually runs on a copy of relocate_kernel.S, which will bring a lot of problems...

It won't be a problem as you can keep all data on-stack without external reference.

Thanks.

- Jiaxun


Above all just my personal thoughts.

Thanks,
Jinyang



_______________________________________________
kexec mailing list
kexec@xxxxxxxxxxxxxxxxxxx
http://lists.infradead.org/mailman/listinfo/kexec




[Index of Archives]     [LM Sensors]     [Linux Sound]     [ALSA Users]     [ALSA Devel]     [Linux Audio Users]     [Linux Media]     [Kernel]     [Gimp]     [Yosemite News]     [Linux Media]

  Powered by Linux