This is a preparation for enabling THP migration.
As the commit b65399f6111b("arm64/mm: Change THP helpers
to comply with generic MM semantics") mentioned, pmd_present()
and pmd_trans_huge() are expected to behave in the following
manner:
-------------------------------------------------------------------------
| PMD states | pmd_present | pmd_trans_huge |
-------------------------------------------------------------------------
| Mapped | Yes | Yes |
-------------------------------------------------------------------------
| Splitting | Yes | Yes |
-------------------------------------------------------------------------
| Migration/Swap | No | No |
-------------------------------------------------------------------------
At present the PROT_NONE bit reuses the READ bit could not comply with
above semantics with two problems:
1. When splitting a PMD THP, PMD is first invalidated with
pmdp_invalidate()->pmd_mkinvalid(), which clears the PRESENT bit
and PROT_NONE bit/READ bit, if the PMD is read-only, then the PAGE_LEAF
property is also cleared, which results in pmd_present() return false.
2. When migrating, the swap entry only clear the PRESENT bit
and PROT_NONE bit/READ bit, the W/X bit may be set, so _PAGE_LEAF may be
true which results in pmd_present() return true.
Solution:
Adjust PROT_NONE bit from READ to GLOBAL bit can satisfy the above rules:
1. GLOBAL bit has no other meanings, not like the R/W/X bit, which is
also relative with _PAGE_LEAF property.
2. GLOBAL bit is at bit 5, making swap entry start from bit 6, bit 0-5
are zero, which means the PRESENT, PROT_NONE, and PAGE_LEAF are
all false, then the pmd_present() and pmd_trans_huge() return false when
in migration/swap.
Signed-off-by: Nanyong Sun <sunnanyong@huawei.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
In riscv, a page table entry is leaf when any bit of read, write,
or execute bit is set. So add a macro:_PAGE_LEAF instead of
(_PAGE_READ | _PAGE_WRITE | _PAGE_EXEC), which is frequently used
to determine if it is a leaf page. This make code easier to read,
without any functional change.
Signed-off-by: Nanyong Sun <sunnanyong@huawei.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
Based on 1 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation version 2 this program is distributed
in the hope that it will be useful but without any warranty without
even the implied warranty of merchantability or fitness for a
particular purpose see the gnu general public license for more
details
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-only
has been chosen to replace the boilerplate/reference in 97 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Alexios Zavras <alexios.zavras@intel.com>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190529141901.025053186@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Previously, invalid PTEs and swap PTEs had the same binary
representation, causing errors when attempting to unmap PROT_NONE
mappings, including implicit unmap on exit.
Typical error:
swap_info_get: Bad swap file entry 40000000007a9879
BUG: Bad page map in process a.out pte:3d4c3cc0 pmd:3e521401
Cc: stable@vger.kernel.org
Signed-off-by: Stefan O'Rear <sorear2@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
This patch contains code to manage the RISC-V MMU, including definitions
of the page tables and the page walking code.
Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
