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authorJoerg Roedel <jroedel@suse.de>2020-08-14 17:19:47 +0200
committerIngo Molnar <mingo@kernel.org>2020-08-15 13:56:16 +0200
commit7a27ef5e83089090f3a4073a9157c862ef00acfc (patch)
tree42c076fe753ccd98691928377b000ac5e980b4b7 /arch/x86/mm
parent58a18fe95e83b8396605154db04d73b08063f31b (diff)
x86/mm/64: Update comment in preallocate_vmalloc_pages()
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
Diffstat (limited to 'arch/x86/mm')
-rw-r--r--arch/x86/mm/init_64.c15
1 files changed, 10 insertions, 5 deletions
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 777d83546764..b5a3fa4033d3 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -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)