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Aneesh Kumar K.V 47b8def935 powerpc/mm: Avoid calling arch_enter/leave_lazy_mmu() in set_ptes
With commit 9fee28baa6 ("powerpc: implement the new page table range
API") we added set_ptes to powerpc architecture. The implementation
included calling arch_enter/leave_lazy_mmu() calls.

The patch removes the usage of arch_enter/leave_lazy_mmu() because
set_pte is not supposed to be used when updating a pte entry. Powerpc
architecture uses this rule to skip the expensive tlb invalidate which
is not needed when you are setting up the pte for the first time. See
commit 56eecdb912 ("mm: Use ptep/pmdp_set_numa() for updating
_PAGE_NUMA bit") for more details

The patch also makes sure we are not using the interface to update a
valid/present pte entry by adding VM_WARN_ON check all the ptes we
are setting up. Furthermore, we add a comment to set_pte_filter to
clarify it can only update folio-related flags and cannot filter
pfn specific details in pte filtering.

Removal of arch_enter/leave_lazy_mmu() also will avoid nesting of
these functions that are not supported. For ex:

remap_pte_range()
  -> arch_enter_lazy_mmu()
  -> set_ptes()
      -> arch_enter_lazy_mmu()
      -> arch_leave_lazy_mmu()
  -> arch_leave_lazy_mmu()

Fixes: 9fee28baa6 ("powerpc: implement the new page table range API")
Signed-off-by: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231024143604.16749-1-aneesh.kumar@linux.ibm.com
2023-10-25 16:08:46 +11:00
arch powerpc/mm: Avoid calling arch_enter/leave_lazy_mmu() in set_ptes 2023-10-25 16:08:46 +11:00
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README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
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Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
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    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.