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| author | Peilin Ye <peilin.ye@bytedance.com> | 2021-08-18 15:01:23 -0700 |
|---|---|---|
| committer | Jonathan Corbet <corbet@lwn.net> | 2021-08-20 11:14:11 -0600 |
| commit | 251a7b3edc197a3947b8cb56fffe61d811aba0a5 (patch) | |
| tree | d20bd8c38816a94ba09eb887fdeda95c239b8934 /Documentation/x86 | |
| parent | d44f571ff5ce51298df520cc46c3a9f5b983fc0a (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.rst | 4 |
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 |