[bug#69899] [PATCH 0/7] support to use `guix system vm' with riscv64.

[Zheng Junjie]

Ludovic Courtès <ludo@gnu.org> writes:

> Hi,
>
> Zheng Junjie <zhengjunjie@iscas.ac.cn> skribis:
>
>> Leo Famulari <leo@famulari.name> writes:
>>
>>> Hi, thanks for these patches!
>>>
>>> On Tue, Mar 19, 2024 at 11:15:53PM +0800, Zheng Junjie wrote:
>>>> hello!. this patchset make `guix system vm --target=riscv64-linux-gnu' 
>>>> work.
>>>> and `guix system vm --system=riscv64-linux` also work, But there is a 
>>>> problem
>>>> that the qemu running with --system=riscv64-linux is also riscv 
>>>> architecture,
>>>> now you have to manually modify to use native qemu or the guix of 
>>>> qemu-system
>>>> on qemu-user is too slow. and must enable qemu-binfmt.
>>>
>>> So, what should we do about the problem? What's the ideal solution for
>>> Guix? I don't have any experience with this subject matter.
>>
>> I've come up with two ideas:
>>
>> 1. Force the current system's qemu to be used, on x86_64 and -s
>> riscv64-linux, use x86_64's qemu.
>> 2. add an environment variable, GUIX_QEMU, to allow the internal qemu
>> execution to be replaced
>>
>> There may be other solutions, but I can't think of them yet.
>
> Thing is, ‘--system=X’ is supposed to be giving the exact same result as
> if you were building natively on X.  Thus, it’s not surprising that
> ‘guix system vm --system=X’ gives on a QEMU binary built for X.
>
> Now, it’s admittedly not very useful in this case.  I believe the
> attached patch implements #1 (I wasn’t able to test it yet because too
> many things had to be built).  How does it sound?

it works, and the following patch is required.

0001-vm-Don-t-add-enable-kvm-when-SYSTEM-and-system-are-n.patch
Description: Text Data

And maybe shebang interpreter also need override %CURRENT-SYSTEM?[1]
Even though when the Shebang interpreter cannot execute, the file will
be interpreted and executed by the current shell.

>
> diff --git a/gnu/system/vm.scm b/gnu/system/vm.scm
> index 7d9d07ebb7..a2743453e7 100644
> --- a/gnu/system/vm.scm
> +++ b/gnu/system/vm.scm
> @@ -287,8 +287,11 @@ (define* (system-qemu-image/shared-store-script os
>        #~(format #f "/tmp/guix-image-~a" (basename #$base-image)))
>  
>      (define qemu-exec
> -      #~(list #+(file-append qemu "/bin/"
> -                             (qemu-command (or target system)))
> +      #~(list #+(with-parameters ((%current-system %system)
> +                                  (%current-target-system #f))
> +                  ;; Override %CURRENT-SYSTEM to always use a native 
> emulator.
> +                  (file-append qemu "/bin/"
> +                               (qemu-command (or target system))))
>                ;; Tells qemu to use the terminal it was started in for IO.
>                #$@(if graphic? '() #~("-nographic"))
>                #$@(if full-boot?
>
>
> Thanks,
> Ludo’.

[1] 
https://git.savannah.gnu.org/cgit/guix.git/tree/gnu/system/vm.scm?h=9e9ec741d0dc5ce58f8d21d31800ff2cafce128f#n328

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