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RE: [PATCH] multiboot2: enable quirk-modules-after-kernel

From: Chen, Zide
Subject: RE: [PATCH] multiboot2: enable quirk-modules-after-kernel
Date: Fri, 3 Apr 2020 06:38:51 +0000

Hi Paul,

Thank you very much for your reply!

We are using Grub to boot ACRN hypervisor. It could run into problem to launch 
large guest Linux kernel.

For example: 
        multiboot2 /boot/acrn.bin
        module2 /boot/bzImage 

In this case, ACRN image is loaded to address 256M according to ACRN's 
multiboot2 address tag, and the guest VM's bzImage is loaded to address 1M 
because Grub allocates memory for multiboot2 module from the lowest address 0. 
When ACRN is launching the guest Linux, it prefers to relocate guest bzImage to 
address 16M and it could have problem if the original bzImage is larger than 
15MB which overlaps with address 16M. 

ACRN has various choices to resolve this problem. Our first choice is to ask 
boot loader to load the modules after the ACRN image since ACRN is a 
lightweight hypervisor and it's always better to have simpler logic and smaller 

BTW, I will update the patch with more descriptions as well.

Best Regards,

> -----Original Message-----
> From: Paul Menzel <address@hidden>
> Sent: Thursday, April 2, 2020 4:40 AM
> To: Chen, Zide <address@hidden>
> Cc: The development of GNU GRUB <address@hidden>
> Subject: Re: [PATCH] multiboot2: enable quirk-modules-after-kernel
> Dear Zide,
> Thank you very much for your patch.
> Am 26.03.20 um 23:46 schrieb Zide Chen:
> > In multiboot2, currently there is no way to control where to load the
> > modules. In case of user wants to reserve low address for specific
> > usage, this quirk is useful.
> It’d be great if you elaborated, where the quirk comes from, and how the
> the change can be tested to reproduce your issue.
> Lastly, it’d be great to also describe your implementation in the commit
> message, so reviewers can verify that too.
> […]
> Kind regards,
> Paul

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