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The idea comes from a discussion between Linus and Andrea [1].
Before this patch we only allow a page fault to retry once. We achieved
this by clearing the FAULT_FLAG_ALLOW_RETRY flag when doing
handle_mm_fault() the second time. This was majorly used to avoid
unexpected starvation of the system by looping over forever to handle the
page fault on a single page. However that should hardly happen, and after
all for each code path to return a VM_FAULT_RETRY we'll first wait for a
condition (during which time we should possibly yield the cpu) to happen
before VM_FAULT_RETRY is really returned.
This patch removes the restriction by keeping the FAULT_FLAG_ALLOW_RETRY
flag when we receive VM_FAULT_RETRY. It means that the page fault handler
now can retry the page fault for multiple times if necessary without the
need to generate another page fault event. Meanwhile we still keep the
FAULT_FLAG_TRIED flag so page fault handler can still identify whether a
page fault is the first attempt or not.
Then we'll have these combinations of fault flags (only considering
ALLOW_RETRY flag and TRIED flag):
- ALLOW_RETRY and !TRIED: this means the page fault allows to
retry, and this is the first try
- ALLOW_RETRY and TRIED: this means the page fault allows to
retry, and this is not the first try
- !ALLOW_RETRY and !TRIED: this means the page fault does not allow
to retry at all
- !ALLOW_RETRY and TRIED: this is forbidden and should never be used
In existing code we have multiple places that has taken special care of
the first condition above by checking against (fault_flags &
FAULT_FLAG_ALLOW_RETRY). This patch introduces a simple helper to detect
the first retry of a page fault by checking against both (fault_flags &
FAULT_FLAG_ALLOW_RETRY) and !(fault_flag & FAULT_FLAG_TRIED) because now
even the 2nd try will have the ALLOW_RETRY set, then use that helper in
all existing special paths. One example is in __lock_page_or_retry(), now
we'll drop the mmap_sem only in the first attempt of page fault and we'll
keep it in follow up retries, so old locking behavior will be retained.
This will be a nice enhancement for current code [2] at the same time a
supporting material for the future userfaultfd-writeprotect work, since in
that work there will always be an explicit userfault writeprotect retry
for protected pages, and if that cannot resolve the page fault (e.g., when
userfaultfd-writeprotect is used in conjunction with swapped pages) then
we'll possibly need a 3rd retry of the page fault. It might also benefit
other potential users who will have similar requirement like userfault
write-protection.
GUP code is not touched yet and will be covered in follow up patch.
Please read the thread below for more information.
[1] https://lore.kernel.org/lkml/20171102193644.GB22686@redhat.com/
[2] https://lore.kernel.org/lkml/20181230154648.GB9832@redhat.com/
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Suggested-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Brian Geffon <bgeffon@google.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Link: http://lkml.kernel.org/r/20200220160246.9790-1-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Many of the privileged CSRs exist in a supervisor and machine version
that are used very similarly. Provide versions of the CSR names and
fields that map to either the S-mode or M-mode variant depending on
a new CONFIG_RISCV_M_MODE kconfig symbol.
Contains contributions from Damien Le Moal <Damien.LeMoal@wdc.com>
and Paul Walmsley <paul.walmsley@sifive.com>.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de> # for drivers/clocksource, drivers/irqchip
[paul.walmsley@sifive.com: updated to apply]
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
Add prototypes for assembly language functions defined in head.S,
and include these prototypes into C source files that call those
functions.
This patch resolves the following warnings from sparse:
arch/riscv/kernel/setup.c:39:10: warning: symbol 'hart_lottery' was not declared. Should it be static?
arch/riscv/kernel/setup.c:42:13: warning: symbol 'parse_dtb' was not declared. Should it be static?
arch/riscv/kernel/smpboot.c:33:6: warning: symbol '__cpu_up_stack_pointer' was not declared. Should it be static?
arch/riscv/kernel/smpboot.c:34:6: warning: symbol '__cpu_up_task_pointer' was not declared. Should it be static?
arch/riscv/mm/fault.c:25:17: warning: symbol 'do_page_fault' was not declared. Should it be static?
This change should have no functional impact.
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
Pull force_sig() argument change from Eric Biederman:
"A source of error over the years has been that force_sig has taken a
task parameter when it is only safe to use force_sig with the current
task.
The force_sig function is built for delivering synchronous signals
such as SIGSEGV where the userspace application caused a synchronous
fault (such as a page fault) and the kernel responded with a signal.
Because the name force_sig does not make this clear, and because the
force_sig takes a task parameter the function force_sig has been
abused for sending other kinds of signals over the years. Slowly those
have been fixed when the oopses have been tracked down.
This set of changes fixes the remaining abusers of force_sig and
carefully rips out the task parameter from force_sig and friends
making this kind of error almost impossible in the future"
* 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (27 commits)
signal/x86: Move tsk inside of CONFIG_MEMORY_FAILURE in do_sigbus
signal: Remove the signal number and task parameters from force_sig_info
signal: Factor force_sig_info_to_task out of force_sig_info
signal: Generate the siginfo in force_sig
signal: Move the computation of force into send_signal and correct it.
signal: Properly set TRACE_SIGNAL_LOSE_INFO in __send_signal
signal: Remove the task parameter from force_sig_fault
signal: Use force_sig_fault_to_task for the two calls that don't deliver to current
signal: Explicitly call force_sig_fault on current
signal/unicore32: Remove tsk parameter from __do_user_fault
signal/arm: Remove tsk parameter from __do_user_fault
signal/arm: Remove tsk parameter from ptrace_break
signal/nds32: Remove tsk parameter from send_sigtrap
signal/riscv: Remove tsk parameter from do_trap
signal/sh: Remove tsk parameter from force_sig_info_fault
signal/um: Remove task parameter from send_sigtrap
signal/x86: Remove task parameter from send_sigtrap
signal: Remove task parameter from force_sig_mceerr
signal: Remove task parameter from force_sig
signal: Remove task parameter from force_sigsegv
...
Pull RISC-V fixes from Paul Walmsley:
"This contains fixes, defconfig, and DT data changes for the v5.2-rc
series.
The fixes are relatively straightforward:
- Addition of a TLB fence in the vmalloc_fault path, so the CPU
doesn't enter an infinite page fault loop
- Readdition of the pm_power_off export, so device drivers that
reassign it can now be built as modules
- A udelay() fix for RV32, fixing a miscomputation of the delay time
- Removal of deprecated smp_mb__*() barriers
This also adds initial DT data infrastructure for arch/riscv, along
with initial data for the SiFive FU540-C000 SoC and the corresponding
HiFive Unleashed board.
We also update the RV64 defconfig to include some core drivers for the
FU540 in the build"
* tag 'riscv-for-v5.2/fixes-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
riscv: remove unused barrier defines
riscv: mm: synchronize MMU after pte change
riscv: dts: add initial board data for the SiFive HiFive Unleashed
riscv: dts: add initial support for the SiFive FU540-C000 SoC
dt-bindings: riscv: convert cpu binding to json-schema
dt-bindings: riscv: sifive: add YAML documentation for the SiFive FU540
arch: riscv: add support for building DTB files from DT source data
riscv: Fix udelay in RV32.
riscv: export pm_power_off again
RISC-V: defconfig: enable clocks, serial console
Because RISC-V compliant implementations can cache invalid entries
in TLB, an SFENCE.VMA is necessary after changes to the page table.
This patch adds an SFENCE.vma for the vmalloc_fault path.
Signed-off-by: ShihPo Hung <shihpo.hung@sifive.com>
[paul.walmsley@sifive.com: reversed tab->whitespace conversion,
wrapped comment lines]
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: linux-riscv@lists.infradead.org
Cc: stable@vger.kernel.org
The do_trap function is always called with tsk == current.
Make that obvious by removing the tsk parameter.
This also makes it clear that do_trap calls force_sig_fault
on the current task.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.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 either version 2 of the license or at
your option any later version 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 you
should have received a copy of the gnu general public license along
with this program if not see the file copying or write to the free
software foundation inc
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-or-later
has been chosen to replace the boilerplate/reference in 12 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190523091651.231300438@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
When a user mode process accesses an address in the vmalloc area
do_page_fault tries to unlock the mmap semaphore when it isn't locked.
Signed-off-by: Andreas Schwab <schwab@suse.de>
[Palmer: Duplicated code instead of a goto]
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
We should prefer accessing CSRs using their CSR numbers because:
1. It compiles fine with older toolchains.
2. We can use latest CSR names in #define macro names of CSR numbers
as-per RISC-V spec.
3. We can access newly added CSRs even if toolchain does not recognize
newly addes CSRs by name.
Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
Pull RISC-V updates from Palmer Dabbelt:
"This contains the fixes we'd like to target for the 4.16 merge window.
It's not as much as I was originally hoping to do but between glibc,
the chip, and FOSDEM there just wasn't enough time to get everything
put together. As such, this merge window is essentially just going to
be small changes. This includes mostly cleanups:
- A build fix failure to the audit test cases.
RISC-V doesn't have renameat because the generic syscall ABI moved
to renameat2 by the time of our port. The syscall audit test cases
don't understand this, so I added a trivial fix. This went through
mailing list review during the 4.15 merge window, but nobody has
picked it up so I think it's best to just do this here.
- The removal of our command-line argument processing code. The
"mem_end" stuff was broken and the rest duplicated generic device
tree code. The generic code was already being called.
- Some unused/redundant code has been removed, including
__ARCH_HAVE_MMU, current_pgdir, and the initialization of
init_mm.pgd.
- SUM is disabled upon taking a trap, which means that user memory is
protected during traps taking inside copy_{to,from}_user().
- The sptbr CSR has been renamed to satp in C code. We haven't
changed the assembly code in order to maintain compatibility with
binutils 2.29, which doesn't understand the new name.
Additionally, we're adding some new features:
- Basic ftrace support, thanks to Alan Kao!
- Support for ZONE_DMA32.
This is necessary for all the normal reasons, but also to deal with
a deficiency in the Xilinx PCIe controller we're using on our
FPGA-based systems. While the ZONE_DMA32 addition should be
sufficient for most uses, it doesn't complete the fix for the
Xilinx controller.
- TLB shootdowns now only target the harts where they're necessary,
instead of applying to all harts in the system.
These patches have all been sitting on our linux-next branch for a
while now. Due to time constraints this is all I feel comfortable
submitting during the 4.16 merge window, hopefully we'll do better
next time!"
[ Note to self: "harts" is RISC-V speak for "hardware threads". I had
to look that up. - Linus ]
* tag 'riscv-for-linus-4.16-merge_window' of git://git.kernel.org/pub/scm/linux/kernel/git/palmer/riscv-linux:
riscv: inline set_pgdir into its only caller
riscv: rename sptbr to satp
riscv: don't read back satp in paging_init
riscv: remove the unused current_pgdir function
riscv: add ZONE_DMA32
RISC-V: Limit the scope of TLB shootdowns
riscv: disable SUM in the exception handler
riscv: remove redundant unlikely()
riscv: remove unused __ARCH_HAVE_MMU define
riscv/ftrace: Add basic support
RISC-V: Remove mem_end command line processing
RISC-V: Remove duplicate command-line parsing logic
audit: Avoid build failures on systems without renameat
Pull asm/uaccess.h whack-a-mole from Al Viro:
"It's linux/uaccess.h, damnit... Oh, well - eventually they'll stop
cropping up..."
* 'work.whack-a-mole' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
asm-prototypes.h: use linux/uaccess.h, not asm/uaccess.h
riscv: use linux/uaccess.h, not asm/uaccess.h...
ppc: for put_user() pull linux/uaccess.h, not asm/uaccess.h
satp is the name used by the current privileged spec 1.10, use it
instead of the old name. The most recent release binutils release
(2.29) doesn't know about the satp name yet, so stick to the name from
the previous privileged ISA release and comment on the fact.
Signed-off-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>
