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Re: UEFI Compatibility Issues in Fedora 10



jonathan barkelew wrote:
UEFI Compatibility Issues in Fedora 10


The second issue is far more pressing, and much more difficult to solve. The linux kernel will behave
incorrectly if more than 400k of runtime memory is declared by system firmware. The kernel attempts
to map all UEFI runtime memory into the kernel fixmap table, and any requests to map more than 400k
are silently ignored. If this memory is accessed later in the boot process (after transition to virtual
mode), the kernel will panic. It is my understanding that this mechanism was designed to enable kexec
functionality, but this mechanism is UEFI non-compliant. If Fedora is ever to be reliably booted on
UEFI systems, this issue must be addressed.

I had gotten this fixed upstream, committed in the 2.6.29-rc8 kernel. efi_ioremap was broken. This should also be in the latest rawhide kernel.
Perhaps you can verify the problem is resolved? If it is not resolved, please let me know.

I've briefly contacted the LKML, but after very little discussion the issue was forgotten. I personally
don't know how to solve the runtime boot problem while still enabling kexec, but it was my hope
that if the Fedora community were involved a solution might be found.

I had not tested the efi_ioremap fixes with kexec. I would appreciate testing feedback if you have any (test with kernel >= 2.6.29-rc8)

Brian


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