From: Peilin Ye <peilin.ye@xxxxxxxxxxxxx>
x86_64 vmalloc() mappings are no longer "synchronized" among page tables
via faulting since commit 6eb82f994026 ("x86/mm: Pre-allocate P4D/PUD
pages for vmalloc area"), since the corresponding P4D or PUD pages are
now preallocated at boot, by preallocate_vmalloc_pages(). Drop the
"lazily synchronized" description for less confusion.
While this file is x86_64-specific, it is worth noting that things are
different for x86_32, where vmalloc()-related changes to `init_mm.pgd` are
synchronized to all page tables in the system during runtime, via
arch_sync_kernel_mappings(). Unfortunately, this synchronization is
subject to race condition, which is further handled via faulting, see
vmalloc_fault(). See commit 4819e15f740e ("x86/mm/32: Bring back vmalloc
faulting on x86_32") for more details.
Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Signed-off-by: Peilin Ye <peilin.ye@xxxxxxxxxxxxx>
---
Hi all,
Resending this with Muchun's Reviewed-by:.
Thanks,
Peilin Ye
Changes in v2:
- More information for x86_32 in commit message (Joerg Roedel
<jroedel@xxxxxxx>)
- Use my new email address for work
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
--
2.20.1
