Re: [edk2-devel] EFI table being corrupted during Kexec

[Breno Leitao <leitao@debian.org>]

Hello Eric,

On Tue, Sep 10, 2024 at 09:26:00AM -0500, Eric W. Biederman wrote:
> > I am wondering if that memory region/range should be part of e820 table that is
> > passed by EFI firmware to kernel, and if it is not passed (as it is not being
> > passed today), then the kernel doesn't need to respect it, and it is free to
> > overwrite (as it does today). In other words, this is a firmware bug and not a
> > kernel bug.
> >
> > Am I missing something?
> 
> I agree that this appears to be a firmware bug.  This memory is reserved
> in one location and not in another location.

That was is our current understanding also, but, having the same issue
in EDK2 and on a real machine firmware was surprising.

Anyway, I've CCed the EDK2 mailing list in this thread as well, let's
see if someone has any comment.

> As I recall the memblock allocator is the bootstrap memory allocator
> used when bringing up the kernel.  So I don't see reserving something
> in the memblock allocator as being authoritative as to how the firmware
> has setup memory.
> 
> I would suggest writing a patch to update whatever is calling
> memblock_reserve to also, or perhaps in preference to update the e820
> map.  If the code is not x86 specific I would suggest using ACPI's
> arch_reserve_mem_area call.

Should all memblock_reserve() memory ranges be mapped to e820 table, or,
just specific cases where we see problems?

Thanks


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