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

From: Zhou Yanjie
Date: Thu Sep 17 2020 - 09:55:45 EST


在 2020/9/17 下午8:41, Jinyang He 写道:
Hi, Huacai,

On 09/16/2020 01:39 PM, Huacai Chen wrote:
Hi, Jinyang,

On Tue, Sep 15, 2020 at 10:17 PM Jinyang He <hejinyang@xxxxxxxxxxx> wrote:

On 09/16/2020 09:33 AM, Jiaxun Yang wrote:
于 2020年9月15日 GMT+08:00 下午9:07:43, Jinyang He <hejinyang@xxxxxxxxxxx> 写到:
Add loongson_kexec_prepare(), loongson_kexec_shutdown() and
loongson_kexec_crashdown() for passing the parameters of kexec_args.

To start loongson64, CPU0 needs 3 parameters:
fw_arg0: the number of cmd.
fw_arg1: cmd structure which seems strange, the cmd array[index]'s
          value is cmd string's address, index >= 1.
fw_arg2: environment.

Secondary CPUs do not need parameter at once. They query their
mailbox to get PC, SP and GP in a loop before CPU0 brings them up
and passes these parameters via mailbox.

loongson_kexec_prepare(): Alloc new memory to save cmd for kexec.
Combine the kexec append option string as cmd structure, and the cmd
struct will be parsed in fw_init_cmdline() of arch/mips/fw/lib/cmdline.c.
image->control_code_page need pointing to a safe memory page. In order to
maintain compatibility for the old firmware the low 2MB is reserverd
and safe for Loongson. So let it points here.

loongson_kexec_shutdown(): Wake up all present CPUs and let them go
to reboot_code_buffer. Pass the kexec parameters to kexec_args.

loongson_crash_shutdown(): Pass the kdump parameters to kexec_args.

The assembly part provide a way like BIOS doing to keep secondary
CPUs in a querying loop.

This patch referenced [1][2][3].

[1] arch/mips/cavium-octeon/setup.c

Co-developed-by: Youling Tang <tangyouling@xxxxxxxxxxx>
Signed-off-by: Youling Tang <tangyouling@xxxxxxxxxxx>
Signed-off-by: Jinyang He <hejinyang@xxxxxxxxxxx>
arch/mips/kernel/relocate_kernel.S | 19 ++++++++
arch/mips/loongson64/reset.c       | 88 ++++++++++++++++++++++++++++++++++++++
2 files changed, 107 insertions(+)

diff --git a/arch/mips/kernel/relocate_kernel.S b/arch/mips/kernel/relocate_kernel.S
index ac87089..061cbfb 100644
--- a/arch/mips/kernel/relocate_kernel.S
+++ b/arch/mips/kernel/relocate_kernel.S
@@ -133,6 +133,25 @@ LEAF(kexec_smp_wait)
+#define MAILBOX_BASE 0x900000003ff01000
Please avoid hardcoded SMP information. You're breaking Loongson 3B support.

Ok, I see. Since my machine is Loongson 3A. I'll send v2
after I test it in 3B.
1, My original version can work on both Loongson-3A and Loongson-3B,
why you modify my patch and hadn't discuss with me?

2, With this single patch both kexec and kdump cannot work reliably,
because kexec need this patch:

    and kdump need my first patch in my original version:

    You may argue that you have tested. Yes, I believe that, I'm not
saying that you haven't test, and I'm not saying that your patch
cannot work, I'm just saying that your patch is not robust.

3, I'm the original author and paying attention to kexec/kdump
continuosly, I will send a new version once the above two patches be
accepted. But you re-send my patch without any communication with me,
why you so impatient?


1, Your original version:

This patch can work on Loongson-3A, I tested it.

But it works wrong after the follow behaviors,
   kexec -l vmlinux --append=cmdline_kexec
   kexec -p vmlinux --append=cmdline_kdump
   kexec -e

What 's wrong with you Loongson guys? Why do you always send patches with the same functions as the original author withou any communication with the original author? Especially the original author of the patch is the maintainer of Loongson64 architecture.

In the past year, Loongson employees have been very active. This is a happy thing, but at the same time, it is confusing that, in addition to always sending patches that others have already sent, many patches send by Loongson employees often with only a few lines (less than 10 lines). I don't think this is a normal phenomenon, is this caused by any other factors? Such as KPIs? If the patches are submitted for this purpose, it is not advisable, this behavior will harm the entire Loongson.

It works but cmdline_kdump merged cmdline_kexec.

And this patch memcpy from fw_arg2 to kexec_envp and later memcpy from
kexec_envp to fw_arg2 when fw_arg2 was not changed, it's redundant.

However, I have not Loongson-3B now, and did not test it. For this patch,
does it work well on Loongson-3B3000/Loongson-3B4000?

2, I have known that problem before your patch:

I also did efforts although I had't committed my patch. It's due to the
hardware issues, and I removed pcie_port_device_remove(). Kexec works
normally on GUI. But it works terriblely on CLI. After this discuss:

What Lukas said helped me. I removed
   drivers/pci/pci-driver.c: pci_device_shutdown(): pci_clear_master...
Kexec works well on CLI also.

For another patch:

I have not 2way or 4way machine, and I did not test it.

3, I try to fix Loongson64 kexec function since I joined the community.
I fell sorry to not do enough research on Loongson64 kexec. My first patch:

It fixed problem about "Crash kernel" which can be traced back to linux-5.4.
At that time, I thought there is no developer work on Kexec. Thus, I did a
lot on Kexec. Are you really continuosly paying attention to kexec/kdump?
With the exploring and developing deep, I found your patch several days ago
after I did a draft patch witch referenced:

There is no doubt that your patch gives me confidence and suggestion while
it gives me worry. As a newcomer, I do not know if should communicate with
you since your patch was committed one year ago. And now it may be a good
chance to do some communication.


- Jinyang.

+    mfc0  t1, CP0_EBASE
+    andi  t1, MIPS_EBASE_CPUNUM
+    dli   t0, MAILBOX_BASE
+    andi  t3, t1, 0x3
+    sll   t3, 8
+    or    t0, t0, t3        /* insert core id */
+    andi  t2, t1, 0xc
+    dsll  t2, 42
+    or    t0, t0, t2        /* insert node id */
+1:  ld    s1, 0x20(t0)      /* get PC via mailbox0 */
+    beqz  s1, 1b
+    ld    sp, 0x28(t0)      /* get SP via mailbox1 */
+    ld    gp, 0x30(t0)      /* get GP via mailbox2 */
+    ld    a1, 0x38(t0)
+    jr    s1
      j               s1
diff --git a/arch/mips/loongson64/reset.c b/arch/mips/loongson64/reset.c
index 3bb8a1e..322c326 100644
--- a/arch/mips/loongson64/reset.c
+++ b/arch/mips/loongson64/reset.c
@@ -47,12 +47,100 @@ static void loongson_halt(void)

+#include <linux/cpu.h>
+#include <linux/kexec.h>
+#include <asm/bootinfo.h>
+#define CONTROL_CODE_PAGE    0xFFFFFFFF80000000UL
+static int kexec_argc;
+static int kdump_argc;
+static void *kexec_argv;
+static void *kdump_argv;
+static int loongson_kexec_prepare(struct kimage *image)
+    int i, offt, argc = 0;
+    int *argv;
+    char *str, *ptr, *bootloader = "kexec";
+    argv = kmalloc(COMMAND_LINE_SIZE, GFP_KERNEL);
+    if (!argv)
+            return -ENOMEM;
+    for (i = 0; i < image->nr_segments; i++) {
+            if (!strncmp(bootloader, (char *)image->segment[i].buf,
+                            strlen(bootloader))) {
+                    argv[argc++] = fw_arg1 + COMMAND_LINE_SIZE/2;
+                    str = (char *)argv + COMMAND_LINE_SIZE/2;
+                    memcpy(str, image->segment[i].buf, COMMAND_LINE_SIZE/2);
+                    ptr = strchr(str, ' ');
+                    while (ptr) {
+                            *ptr = '\0';
+                            if (ptr[1] != ' ') {
+                                    offt = (int)(ptr - str + 1);
+                                    argv[argc++] = fw_arg1 + COMMAND_LINE_SIZE/2 + offt;
+                            }
+                            ptr = strchr(ptr + 1, ' ');
+                    }
+                    break;
+            }
+    }
+    /* Kexec/kdump needs a safe page to save reboot_code_buffer. */
+    image->control_code_page = virt_to_page((void *)CONTROL_CODE_PAGE);
+    if (image->type == KEXEC_TYPE_CRASH) {
+            kfree(kdump_argv);
+            kdump_argc = argc;
+            kdump_argv = argv;
+    } else {
+            kfree(kexec_argv);
+            kexec_argc = argc;
+            kexec_argv = argv;
+    }
+    return 0;
+static void loongson_kexec_shutdown(void)
+#ifdef CONFIG_SMP
+    bringup_nonboot_cpus(loongson_sysconf.nr_cpus);
+    fw_arg0 = kexec_argc;
+    memcpy((void *)fw_arg1, kexec_argv, COMMAND_LINE_SIZE);
+    kexec_args[0] = fw_arg0;
+    kexec_args[1] = fw_arg1;
+    kexec_args[2] = fw_arg2;
+static void loongson_crash_shutdown(struct pt_regs *regs)
+    default_machine_crash_shutdown(regs);
+    fw_arg0 = kdump_argc;
+    memcpy((void *)fw_arg1, kdump_argv, COMMAND_LINE_SIZE);
+    kexec_args[0] = fw_arg0;
+    kexec_args[1] = fw_arg1;
+    kexec_args[2] = fw_arg2;
static int __init mips_reboot_setup(void)
      _machine_restart = loongson_restart;
      _machine_halt = loongson_halt;
      pm_power_off = loongson_poweroff;

+    _machine_kexec_prepare = loongson_kexec_prepare;
+    _machine_kexec_shutdown = loongson_kexec_shutdown;
+    _machine_crash_shutdown = loongson_crash_shutdown;
      return 0;