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a3c6018e56
Debugging and original patch from Nick Piggin <npiggin@suse.de> The early fixmap pmd entry inserted at the very top of the KVA is causing the subsequent fixmap mapping code to not provide physically linear pte pages over the kmap atomic portion of the fixmap (which relies on said property to calculate pte addresses). This has caused weird boot failures in kmap_atomic much later in the boot process (initial userspace faults) on a 32-bit PAE system with a larger number of CPUs (smaller CPU counts tend not to run over into the next page so don't show up the problem). Solve this by attempting to clear out the page table, and copy any of its entries to the new one. Also, add a bug if a nonlinear condition is encountered and can't be resolved, which might save some hours of debugging if this fragile scheme ever breaks again... Once we have such logic, we can also use it to eliminate the early ioremap trickery around the page table setup for the fixmap area. This also fixes potential issues with FIX_* entries sharing the leaf page table with the early ioremap ones getting discarded by early_ioremap_clear() and not restored by early_ioremap_reset(). It at once eliminates the temporary (and configuration, namely NR_CPUS, dependent) unavailability of early fixed mappings during the time the fixmap area page tables get constructed. Finally, also replace the hard coded calculation of the initial table space needed for the fixmap area with a proper one, allowing kernels configured for large CPU counts to actually boot. Based-on: Nick Piggin <npiggin@suse.de> Signed-off-by: Jan Beulich <jbeulich@novell.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> |
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