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1f299fad1e
We carry a quirk in the x86 EFI code to switch back to an older method of mapping the EFI runtime services memory regions, because it was deemed risky at the time to implement a new method without providing a fallback to the old method in case problems arose. Such problems did arise, but they appear to be limited to SGI UV1 machines, and so these are the only ones for which the fallback gets enabled automatically (via a DMI quirk). The fallback can be enabled manually as well, by passing efi=old_map, but there is very little evidence that suggests that this is something that is being relied upon in the field. Given that UV1 support is not enabled by default by the distros (Ubuntu, Fedora), there is no point in carrying this fallback code all the time if there are no other users. So let's move it into the UV support code, and document that efi=old_map now requires this support code to be enabled. Note that efi=old_map has been used in the past on other SGI UV machines to work around kernel regressions in production, so we keep the option to enable it by hand, but only if the kernel was built with UV support. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20200113172245.27925-8-ardb@kernel.org |
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