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

[RuiRui Yang]

On Mon, 27 Nov 2023 at 09:53, RuiRui Yang <ruyang at redhat.com> wrote:
>
> 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

Correct about my English wording a bit, I meant about rusty knowledge
of kexec details and newbish loongarch knowledge,
BTW, the webmail often randomly choose the sender email, I usually use
another email for community, that is Dave Young <dyoung at redhat.com>,
same person ;)

Anyway, since this is loongarch specific, it would be better to leave
you guys the arch people to see how to fix it better.

> 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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> >