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x86/boot/32: Temporarily map initrd for microcode loading
Early microcode loading on 32-bit runs in physical address mode because the initrd is not covered by the initial page tables. That results in a horrible mess all over the microcode loader code. Provide a temporary mapping for the initrd in the initial page tables by appending it to the actual initial mapping starting with a new PGD or PMD depending on the configured page table levels ([non-]PAE). The page table entries are located after _brk_end so they are not permanently using memory space. The mapping is invalidated right away in i386_start_kernel() after the early microcode loader has run. This prepares for removing the physical address mode oddities from all over the microcode loader code, which in turn allows further cleanups. Provide the map and unmap code and document the place where the microcode loader needs to be invoked with a comment. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/20231017211722.292291436@linutronix.de
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Thomas Gleixner
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Borislav Petkov (AMD)
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Oct 18, 2023
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