x86_64 vmalloc() mappings are no longer "lazily synchronized" among page
tables via page fault handling since commit 7f0a002b5a21 ("x86/mm: remove
vmalloc faulting"). Subsequently, commit 6eb82f994026 ("x86/mm:
Pre-allocate P4D/PUD pages for vmalloc area") rendered it unnecessary to
synchronize, whether lazily or not, x86_64 vmalloc() mappings at runtime,
since the corresponding P4D or PUD pages are now preallocated during
system initialization by preallocate_vmalloc_pages(). Drop the "lazily
synchronized" description for less confusion.
It is worth noting, however, that there is still a slight complication for
x86_32; see commit 4819e15f740e ("x86/mm/32: Bring back vmalloc faulting
on x86_32") for details.
Signed-off-by: Peilin Ye <yepeilin.cs@xxxxxxxxx>
---
Hi all,
I was trying to understand vmalloc() when I saw this "lazily synchronized"
statement, which confused me for a while. Please correct me if my
understanding is wrong or out of date.
Thank you,
Peilin Ye
Documentation/x86/x86_64/mm.rst | 4 ----
1 file changed, 4 deletions(-)
diff --git a/Documentation/x86/x86_64/mm.rst b/Documentation/x86/x86_64/mm.rst
index ede1875719fb..9798676bb0bf 100644
--- a/Documentation/x86/x86_64/mm.rst
+++ b/Documentation/x86/x86_64/mm.rst
@@ -140,10 +140,6 @@ The direct mapping covers all memory in the system up to the highest
memory address (this means in some cases it can also include PCI memory
holes).
-vmalloc space is lazily synchronized into the different PML4/PML5 pages of
-the processes using the page fault handler, with init_top_pgt as
-reference.
-
We map EFI runtime services in the 'efi_pgd' PGD in a 64Gb large virtual
memory window (this size is arbitrary, it can be raised later if needed).
The mappings are not part of any other kernel PGD and are only available
--
2.25.1
