[PATCH v2] LoongArch: Load vmlinux.efi to the link address

[RuiRui Yang]

On Sat, 25 Nov 2023 at 14:54, WANG Rui <wangrui at loongson.cn> wrote:
>
> Currently, kexec loads vmlinux.efi to address 0 instead of the link
> address. This causes kexec to fail to boot the new vmlinux.efi on qemu.
>
>   pei_loongarch_load: kernel_segment: 0000000000000000
>   pei_loongarch_load: kernel_entry:   00000000013f1000
>   pei_loongarch_load: image_size:     0000000001ca0000
>   pei_loongarch_load: text_offset:    0000000000200000
>   pei_loongarch_load: phys_offset:    0000000000000000
>   pei_loongarch_load: PE format:      yes
>   loongarch_load_other_segments:333: command_line: kexec console=ttyS0,115200
>   kexec_load: entry = 0x13f1000 flags = 0x1020000
>   nr_segments = 2
>   segment[0].buf   = 0x7fffeea38010
>   segment[0].bufsz = 0x1b55200
>   segment[0].mem   = (nil)
>   segment[0].memsz = 0x1ca0000
>   segment[1].buf   = 0x5555570940b0
>   segment[1].bufsz = 0x200
>   segment[1].mem   = 0x1ca0000
>   segment[1].memsz = 0x4000
>
> This patch constrains the range of the kernel segment by `hole_min`
> and `hole_max` to place vmlinux.efi exactly at the link address.
>
>   pei_loongarch_load: kernel_segment: 0000000000200000
>   pei_loongarch_load: kernel_entry:   00000000013f1000
>   pei_loongarch_load: image_size:     0000000001ca0000
>   pei_loongarch_load: text_offset:    0000000000200000
>   pei_loongarch_load: phys_offset:    0000000000000000
>   pei_loongarch_load: PE format:      yes
>   loongarch_load_other_segments:339: command_line: kexec console=ttyS0,115200
>   kexec_load: entry = 0x13f1000 flags = 0x1020000
>   nr_segments = 2
>   segment[0].buf   = 0x7ffff2028010
>   segment[0].bufsz = 0x1b55200
>   segment[0].mem   = 0x200000
>   segment[0].memsz = 0x1ca0000
>   segment[1].buf   = 0x555557498098
>   segment[1].bufsz = 0x200
>   segment[1].mem   = 0x1ea0000
>   segment[1].memsz = 0x4000
>
> Signed-off-by: WANG Rui <wangrui at loongson.cn>
> ---
>
> v1->v2:
>  * Fix the issue preventing it from working on the physical machine.
>
>  kexec/arch/loongarch/kexec-loongarch.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/kexec/arch/loongarch/kexec-loongarch.c b/kexec/arch/loongarch/kexec-loongarch.c
> index 62ff8fd..32a42d2 100644
> --- a/kexec/arch/loongarch/kexec-loongarch.c
> +++ b/kexec/arch/loongarch/kexec-loongarch.c
> @@ -265,9 +265,13 @@ unsigned long loongarch_locate_kernel_segment(struct kexec_info *info)
>                         hole = ULONG_MAX;
>                 }
>         } else {
> -               hole = locate_hole(info,
> -                       loongarch_mem.text_offset + loongarch_mem.image_size,
> -                       MiB(1), 0, ULONG_MAX, 1);
> +               unsigned long hole_min;
> +               unsigned long hole_max;
> +
> +               hole_min = loongarch_mem.text_offset;
> +               hole_max = hole_min + loongarch_mem.image_size;
> +               hole = locate_hole(info, loongarch_mem.image_size,
> +                       MiB(1), hole_min, hole_max, 1);
>
>                 if (hole == ULONG_MAX)
>                         dbgprintf("%s: locate_hole failed\n", __func__);

Hi,

Previously when I played with the zboot kernel on a kvm guest I
noticed this issue, but I found that the 1st 2M memory is memblock
reserved but it is not shown in /proc/iomem as reserved, I suspect the
1st 2M is not usable for some arch specific reason but I was not sure.
  Below patch can fix it but due to my rusty knowledge of loongarch I
did not send it out. I suspect even if the locate_hole avoids the
wrong memory, in the 2nd kernel it could still access it.  Correct?

Index: linux/arch/loongarch/kernel/mem.c
===================================================================
--- linux.orig/arch/loongarch/kernel/mem.c      2023-06-02
10:24:09.633593320 +0800
+++ linux/arch/loongarch/kernel/mem.c   2023-10-05 15:27:05.609455460 +0800
@@ -52,8 +52,8 @@
        memblock_set_current_limit(PFN_PHYS(max_low_pfn));
        memblock_set_node(0, PHYS_ADDR_MAX, &memblock.memory, 0);

-       /* Reserve the first 2MB */
-       memblock_reserve(PHYS_OFFSET, 0x200000);
+       /* Mark the first 2MB as nomap */
+       memblock_mark_nomap(PHYS_OFFSET, 0x200000);

        /* Reserve the kernel text/data/bss */
        memblock_reserve(__pa_symbol(&_text),


> --
> 2.42.0
>
>
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