linux-kernel - Re: [PATCH 3/6] LoongArch/kexec

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Message-ID: <CAAhV-H4_9r=dG=mDU-s2thbv8agoso51U0kHXtx15gxt_wZwVw@mail.gmail.com>
Date: Tue, 12 Aug 2025 11:03:56 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Youling Tang <youling.tang@...ux.dev>
Cc: WANG Xuerui <kernel@...0n.name>, Baoquan He <bhe@...hat.com>, kexec@...ts.infradead.org, 
	loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	Youling Tang <tangyouling@...inos.cn>
Subject: Re: [PATCH 3/6] LoongArch/kexec_file: Add initrd loading

On Tue, Aug 12, 2025 at 10:38 AM Youling Tang <youling.tang@...ux.dev> wrote:
>
> Hi, Huacai
> On 2025/8/11 22:12, Huacai Chen wrote:
> > Hi, Youling,
> >
> > On Mon, Aug 11, 2025 at 5:28 PM Youling Tang <youling.tang@...ux.dev> wrote:
> >> From: Youling Tang <tangyouling@...inos.cn>
> >>
> >> Add inird loading support and pass it to the second kernel via the
> >> cmdline 'initrd=start,size'.
> > I think Patch-3 and Patch-5 should be merged into Patch-2.
> Not all cases require loading initrd, so Patch-2 is a runnable basic patch.
> Separating it into different patches makes it easier to understand and
> review the code.
Unnecessary, without separating the code is clear enough.

>
> Patch-5 coming out separately can better illustrate the role of "mem"
> parameters in capturing the kernel.
Emm, Patch-5 should be squashed to Patch-4, not Patch-2.

Huacai

>
> Youling.
> >
> > Huacai
> >
> >> Signed-off-by: Youling Tang <tangyouling@...inos.cn>
> >> ---
> >>   arch/loongarch/kernel/machine_kexec_file.c | 71 ++++++++++++++++++++++
> >>   1 file changed, 71 insertions(+)
> >>
> >> diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c
> >> index bc91ae0afa4c..e1240644f529 100644
> >> --- a/arch/loongarch/kernel/machine_kexec_file.c
> >> +++ b/arch/loongarch/kernel/machine_kexec_file.c
> >> @@ -34,13 +34,84 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
> >>          return kexec_image_post_load_cleanup_default(image);
> >>   }
> >>
> >> +/* Adds the "initrd=start,size" command line parameter to command line. */
> >> +static void cmdline_add_initrd(struct kimage *image, unsigned long *cmdline_tmplen,
> >> +                               char *modified_cmdline, unsigned long initrd)
> >> +{
> >> +       int initrd_strlen;
> >> +
> >> +       initrd_strlen = sprintf(modified_cmdline + (*cmdline_tmplen), "initrd=0x%lx,0x%lx ",
> >> +               initrd, image->initrd_buf_len);
> >> +       *cmdline_tmplen += initrd_strlen;
> >> +}
> >> +
> >> +/*
> >> + * Tries to add the initrd to the image. If it is not possible to find
> >> + * valid locations, this function will undo changes to the image and return non
> >> + * zero.
> >> + */
> >>   int load_other_segments(struct kimage *image,
> >>                          unsigned long kernel_load_addr,
> >>                          unsigned long kernel_size,
> >>                          char *initrd, unsigned long initrd_len,
> >>                          char *cmdline, unsigned long cmdline_len)
> >>   {
> >> +       struct kexec_buf kbuf;
> >> +       unsigned long orig_segments = image->nr_segments;
> >> +       char *modified_cmdline = NULL;
> >> +       unsigned long cmdline_tmplen = 0;
> >> +       unsigned long initrd_load_addr = 0;
> >> +       int ret = 0;
> >> +
> >> +
> >> +       kbuf.image = image;
> >> +       /* not allocate anything below the kernel */
> >> +       kbuf.buf_min = kernel_load_addr + kernel_size;
> >> +
> >> +       modified_cmdline = kzalloc(COMMAND_LINE_SIZE, GFP_KERNEL);
> >> +       if (!modified_cmdline)
> >> +               return -EINVAL;
> >> +
> >> +       /* Ensure it's nul terminated */
> >> +       modified_cmdline[COMMAND_LINE_SIZE - 1] = '\0';
> >> +
> >> +       /* load initrd */
> >> +       if (initrd) {
> >> +               kbuf.buffer = initrd;
> >> +               kbuf.bufsz = initrd_len;
> >> +               kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
> >> +               kbuf.memsz = initrd_len;
> >> +               kbuf.buf_align = 0;
> >> +               /* within 1GB-aligned window of up to 32GB in size */
> >> +               kbuf.buf_max = round_down(kernel_load_addr, SZ_1G)
> >> +                                               + (unsigned long)SZ_1G * 32;
> >> +               kbuf.top_down = false;
> >> +
> >> +               ret = kexec_add_buffer(&kbuf);
> >> +               if (ret)
> >> +                       goto out_err;
> >> +               initrd_load_addr = kbuf.mem;
> >> +
> >> +               kexec_dprintk("Loaded initrd at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
> >> +                             initrd_load_addr, kbuf.bufsz, kbuf.memsz);
> >> +
> >> +               /* Add the initrd=start,size parameter to the command line */
> >> +               cmdline_add_initrd(image, &cmdline_tmplen, modified_cmdline, initrd_load_addr);
> >> +       }
> >> +
> >> +       if (cmdline_len + cmdline_tmplen > COMMAND_LINE_SIZE) {
> >> +               pr_err("Appending kdump cmdline exceeds cmdline size\n");
> >> +               ret = -EINVAL;
> >> +               goto out_err;
> >> +       }
> >> +       memcpy(modified_cmdline + cmdline_tmplen, cmdline, cmdline_len);
> >> +       cmdline = modified_cmdline;
> >>          image->arch.cmdline_ptr = (unsigned long)cmdline;
> >>
> >>          return 0;
> >> +
> >> +out_err:
> >> +       image->nr_segments = orig_segments;
> >> +       kfree(modified_cmdline);
> >> +       return ret;
> >>   }
> >> --
> >> 2.34.1
> >>