linux-kernel - Re: [PATCH] x86/efi: update e820 about reserved EFI boot services data to fix kexec breakage

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Date:   Thu, 5 Dec 2019 22:15:32 +0100
From:   Michael Weiser <michael@...ser.dinsnail.net>
To:     Dave Young <dyoung@...hat.com>
Cc:     Ingo Molnar <mingo@...nel.org>, linux-efi@...r.kernel.org,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        kexec@...ts.infradead.org, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86/efi: update e820 about reserved EFI boot services
 data to fix kexec breakage

On Thu, Dec 05, 2019 at 06:55:45PM +0800, Dave Young wrote:

> >    esrt: Unsupported ESRT version 2904149718861218184.
> > 
> >  The ESRT memory stays in EFI boot services data, and it was reserved
> >  in kernel via efi_mem_reserve().  The initial purpose of the reservation
> >  is to reuse the EFI boot services data across kexec reboot. For example
> >  the BGRT image data and some ESRT memory like Michael reported.
> > 
> >  But although the memory is reserved it is not updated in the X86 E820 table,
> >  and kexec_file_load() iterates system RAM in the IO resource list to find places
> >  for kernel, initramfs and other stuff. In Michael's case the kexec loaded
> >  initramfs overwrote the ESRT memory and then the failure happened.
> > 
> >  Since kexec_file_load() depends on the E820 table being updated, just fix this
> >  by updating the reserved EFI boot services memory as reserved type in E820.
> Thanks for the amending, also thank all for the review and test.

Same from me, particularly everyone's patience with my haphazard
guesswork around an area I clearly know nothing about. :)
-- 
Thanks,
Michael