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Re: [PATCH] badram filtering

From: phcoder
Subject: Re: [PATCH] badram filtering
Date: Tue, 10 Mar 2009 13:56:51 +0100
User-agent: Thunderbird (X11/20090105)

Very interesting. I have following suggestions:
1) define platform independent way to enumerate memory map. This function wouldn't mark types with GRUB_MACHINE_* but with one of the following types: GRUB_MMAP_HOLE - means that at this position there is no RAM at all. Should this be iterated at all?
GRUB_MMAP_IO - usable only by I/O drivers
GRUB_MMAP_FREE - usable by ACPI and firmware-unaware OS. But may be unusable by grub itself. memory allocator should be used for requesting memory in grub
GRUB_MMAP_ACPI - usable by ACPI-aware OS after loading tables
GRUB_MMAP_PLATFORM_FIRST...GRUB_MMAP_PLATFORM_LAST - platform specific types which can't be used except by firmware-aware code and OS 2) when badram variable is set corresponding memory chunks should be removed from memory manager 3) add a method to specify badram in init.c so that grub2 itself has no risk of using any of this memory. I propose to embed initial environment in core.img. Then prefix and root can be changed to use this mechanism. It would also be able to override this initial environment through multiboot command line when grub2 is loaded by multiboot loader

Robert Millan wrote:

This patch implements badram filtering in GRUB.  It's the same idea as in but applied to GRUB.

The badram module sits between loaders (or other users like lsmmap) and
filters the mmap entries, but only when user previously set the "badram"
variable (whose syntax is the same as the one in badram patch for Linux).

NOTE this won't affect loadees that get the memory map from BIOS instead
of from GRUB.  This means it currently works for Multiboot and for the
new/experimental Linux loader.


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Vladimir 'phcoder' Serbinenko

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