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authorPeilin Ye <peilin.ye@bytedance.com>2021-08-18 15:01:23 -0700
committerJonathan Corbet <corbet@lwn.net>2021-08-20 11:14:11 -0600
commit251a7b3edc197a3947b8cb56fffe61d811aba0a5 (patch)
treed20bd8c38816a94ba09eb887fdeda95c239b8934 /Documentation/x86
parentd44f571ff5ce51298df520cc46c3a9f5b983fc0a (diff)
docs: x86: Remove obsolete information about x86_64 vmalloc() faulting
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@bytedance.com> Signed-off-by: Peilin Ye <peilin.ye@bytedance.com> Reviewed-by: Joerg Roedel <jroedel@suse.de> Link: https://lore.kernel.org/r/20210818220123.2623-1-yepeilin.cs@gmail.com Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/x86')
-rw-r--r--Documentation/x86/x86_64/mm.rst4
1 files changed, 0 insertions, 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