Fix PMM handling of 4K frames #335
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Signed-off-by: Pawel Wieczorkiewicz <[email protected]>
Using public API (get_free_frame() and get_free_page()) in the very internal new_frames_array() is a bad idea. The new frames array allocation can be triggered from within the public API functions, while the PMM lock is already taken. This obviously leads to a deadlock. Signed-off-by: Pawel Wieczorkiewicz <[email protected]>
If there is not enough early frames (or for whatever reason the frame physical address is big enough), it might be the case that such frame mapping does not fit into the relatively small KERNEL_BASE area. It is better to always map in the large enough KERNEL_MAP area. The early frames arrays (before the final page tables are created) have to be mapped into the KERNEL_BASE area as this is the only space covered by boot time page tables (see EARLY_VIRT_MEM settings). Signed-off-by: Pawel Wieczorkiewicz <[email protected]>
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Nov 24, 2023
If we run out of 4k frames it becomes impossible to perform a higher order frames splitting, since new frames creation may need new frames array, which is 4k as well. To prevent these kind of situations, always keep at least two free 4k frames available.
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