x86/mm/64: Update comment in preallocate_vmalloc_pages() (7a27ef5e) · Commits · 戴 / test

The comment explaining why 4-level systems only need to allocate on the P4D level caused some confustion. Update it to better explain why on 4-level systems the allocation on PUD level is necessary. Signed-off-by:

Joerg Roedel <jroedel@suse.de> Signed-off-by:

Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20200814151947.26229-3-joro@8bytes.org

arch/x86/mm/init_64.c

+10 −5

Original line number	Diff line number	Diff line
		@@ -1252,14 +1252,19 @@ static void __init preallocate_vmalloc_pages(void)
		if (!p4d)
		goto failed;

		/*
		* With 5-level paging the P4D level is not folded. So the PGDs
		* are now populated and there is no need to walk down to the
		* PUD level.
		*/
		if (pgtable_l5_enabled())
		continue;

		/*
		* The goal here is to allocate all possibly required
		* hardware page tables pointed to by the top hardware
		* level.
		*
		* On 4-level systems, the P4D layer is folded away and
		* the above code does no preallocation. Below, go down
		* to the pud _software_ level to ensure the second
		* hardware level is allocated on 4-level systems too.
		*/
		lvl = "pud";
		pud = pud_alloc(&init_mm, p4d, addr);
		if (!pud)

Admin message