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

[Simon Horman <horms@kernel.org>]

On Fri, Dec 01, 2023 at 10:54:49PM +0800, Huacai Chen wrote:
> Hi, Simon,
> 
> On Fri, Dec 1, 2023 at 10:06 PM Simon Horman <horms@kernel.org> wrote:
> >
> > On Wed, Nov 29, 2023 at 12:15:17PM +0800, Huacai Chen wrote:
> > > Hi, all,
> > >
> > > On Tue, Nov 28, 2023 at 2:27 PM WANG Rui <wangrui@loongson.cn> wrote:
> > > >
> > > > Hi,
> > > >
> > > > On Mon, Nov 27, 2023 at 10:36 AM RuiRui Yang <ruyang@redhat.com> wrote:
> > > > >
> > > > > On Mon, 27 Nov 2023 at 09:53, RuiRui Yang <ruyang@redhat.com> wrote:
> > > > > >
> > > > > > On Sat, 25 Nov 2023 at 14:54, WANG Rui <wangrui@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@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@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?
> > > >
> > > > I can confirm that the mapping of the 1st 2M in iomem on qemu causes
> > > > kexec to not work. The root cause is that LoongArch's vmlinux.efi can
> > > > only run on the link address, which is why I limit the allocation
> > > > location of the kernel segment through hole min/max, not the kernel's
> > > > iomem.
> > > >
> > > > Hucai, what do you think about the 1st 2M mapping type in the kernel?
> > > I agree with WANG Rui, this should be fixed in kexec-tools, and
> > > 'nomap' is not for such a usage.
> >
> > Can I confirm that you'd still like this patch applied?
> Yes, v1 breaks the real machine, while v2 works on both real machine and qemu.

Thanks, applied.

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