On Wed, Aug 18, 2021 at 03:01:23PM -0700, Peilin Ye wrote:
> 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>
Reviewed-by: Joerg Roedel <jroedel@xxxxxxx>
> ---
> 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
>
