From: Peilin Ye Date: Wed, 18 Aug 2021 22:01:23 +0000 (-0700) Subject: docs: x86: Remove obsolete information about x86_64 vmalloc() faulting X-Git-Tag: v5.15~323^2~13 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=251a7b3edc197a3947b8cb56fffe61d811aba0a5;p=platform%2Fkernel%2Flinux-starfive.git 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 Signed-off-by: Peilin Ye Reviewed-by: Joerg Roedel Link: https://lore.kernel.org/r/20210818220123.2623-1-yepeilin.cs@gmail.com Signed-off-by: Jonathan Corbet --- diff --git a/Documentation/x86/x86_64/mm.rst b/Documentation/x86/x86_64/mm.rst index ede1875..9798676 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