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![Peter Xu](/assets/img/avatar_default.png)
Patch series "mm: Page fault accounting cleanups", v5.
This is v5 of the pf accounting cleanup series. It originates from Gerald
Schaefer's report on an issue a week ago regarding to incorrect page fault
accountings for retried page fault after commit 4064b98270
("mm: allow
VM_FAULT_RETRY for multiple times"):
https://lore.kernel.org/lkml/20200610174811.44b94525@thinkpad/
What this series did:
- Correct page fault accounting: we do accounting for a page fault
(no matter whether it's from #PF handling, or gup, or anything else)
only with the one that completed the fault. For example, page fault
retries should not be counted in page fault counters. Same to the
perf events.
- Unify definition of PERF_COUNT_SW_PAGE_FAULTS: currently this perf
event is used in an adhoc way across different archs.
Case (1): for many archs it's done at the entry of a page fault
handler, so that it will also cover e.g. errornous faults.
Case (2): for some other archs, it is only accounted when the page
fault is resolved successfully.
Case (3): there're still quite some archs that have not enabled
this perf event.
Since this series will touch merely all the archs, we unify this
perf event to always follow case (1), which is the one that makes most
sense. And since we moved the accounting into handle_mm_fault, the
other two MAJ/MIN perf events are well taken care of naturally.
- Unify definition of "major faults": the definition of "major
fault" is slightly changed when used in accounting (not
VM_FAULT_MAJOR). More information in patch 1.
- Always account the page fault onto the one that triggered the page
fault. This does not matter much for #PF handlings, but mostly for
gup. More information on this in patch 25.
Patchset layout:
Patch 1: Introduced the accounting in handle_mm_fault(), not enabled.
Patch 2-23: Enable the new accounting for arch #PF handlers one by one.
Patch 24: Enable the new accounting for the rest outliers (gup, iommu, etc.)
Patch 25: Cleanup GUP task_struct pointer since it's not needed any more
This patch (of 25):
This is a preparation patch to move page fault accountings into the
general code in handle_mm_fault(). This includes both the per task
flt_maj/flt_min counters, and the major/minor page fault perf events. To
do this, the pt_regs pointer is passed into handle_mm_fault().
PERF_COUNT_SW_PAGE_FAULTS should still be kept in per-arch page fault
handlers.
So far, all the pt_regs pointer that passed into handle_mm_fault() is
NULL, which means this patch should have no intented functional change.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Cain <bcain@codeaurora.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Guo Ren <guoren@kernel.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: James E.J. Bottomley <James.Bottomley@HansenPartnership.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Ley Foon Tan <ley.foon.tan@intel.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Nick Hu <nickhu@andestech.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Stafford Horne <shorne@gmail.com>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vincent Chen <deanbo422@gmail.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Link: http://lkml.kernel.org/r/20200707225021.200906-1-peterx@redhat.com
Link: http://lkml.kernel.org/r/20200707225021.200906-2-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
595 lines
17 KiB
C
595 lines
17 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Copyright 2013 Red Hat Inc.
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*
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* Authors: Jérôme Glisse <jglisse@redhat.com>
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*/
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/*
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* Refer to include/linux/hmm.h for information about heterogeneous memory
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* management or HMM for short.
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*/
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#include <linux/pagewalk.h>
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#include <linux/hmm.h>
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#include <linux/init.h>
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#include <linux/rmap.h>
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#include <linux/swap.h>
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#include <linux/slab.h>
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#include <linux/sched.h>
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#include <linux/mmzone.h>
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#include <linux/pagemap.h>
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#include <linux/swapops.h>
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#include <linux/hugetlb.h>
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#include <linux/memremap.h>
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#include <linux/sched/mm.h>
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#include <linux/jump_label.h>
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#include <linux/dma-mapping.h>
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#include <linux/mmu_notifier.h>
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#include <linux/memory_hotplug.h>
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struct hmm_vma_walk {
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struct hmm_range *range;
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unsigned long last;
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};
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enum {
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HMM_NEED_FAULT = 1 << 0,
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HMM_NEED_WRITE_FAULT = 1 << 1,
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HMM_NEED_ALL_BITS = HMM_NEED_FAULT | HMM_NEED_WRITE_FAULT,
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};
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static int hmm_pfns_fill(unsigned long addr, unsigned long end,
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struct hmm_range *range, unsigned long cpu_flags)
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{
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unsigned long i = (addr - range->start) >> PAGE_SHIFT;
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for (; addr < end; addr += PAGE_SIZE, i++)
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range->hmm_pfns[i] = cpu_flags;
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return 0;
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}
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/*
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* hmm_vma_fault() - fault in a range lacking valid pmd or pte(s)
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* @addr: range virtual start address (inclusive)
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* @end: range virtual end address (exclusive)
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* @required_fault: HMM_NEED_* flags
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* @walk: mm_walk structure
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* Return: -EBUSY after page fault, or page fault error
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*
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* This function will be called whenever pmd_none() or pte_none() returns true,
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* or whenever there is no page directory covering the virtual address range.
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*/
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static int hmm_vma_fault(unsigned long addr, unsigned long end,
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unsigned int required_fault, struct mm_walk *walk)
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{
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struct hmm_vma_walk *hmm_vma_walk = walk->private;
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struct vm_area_struct *vma = walk->vma;
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unsigned int fault_flags = FAULT_FLAG_REMOTE;
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WARN_ON_ONCE(!required_fault);
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hmm_vma_walk->last = addr;
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if (required_fault & HMM_NEED_WRITE_FAULT) {
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if (!(vma->vm_flags & VM_WRITE))
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return -EPERM;
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fault_flags |= FAULT_FLAG_WRITE;
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}
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for (; addr < end; addr += PAGE_SIZE)
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if (handle_mm_fault(vma, addr, fault_flags, NULL) &
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VM_FAULT_ERROR)
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return -EFAULT;
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return -EBUSY;
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}
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static unsigned int hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
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unsigned long pfn_req_flags,
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unsigned long cpu_flags)
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{
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struct hmm_range *range = hmm_vma_walk->range;
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/*
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* So we not only consider the individual per page request we also
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* consider the default flags requested for the range. The API can
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* be used 2 ways. The first one where the HMM user coalesces
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* multiple page faults into one request and sets flags per pfn for
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* those faults. The second one where the HMM user wants to pre-
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* fault a range with specific flags. For the latter one it is a
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* waste to have the user pre-fill the pfn arrays with a default
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* flags value.
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*/
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pfn_req_flags &= range->pfn_flags_mask;
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pfn_req_flags |= range->default_flags;
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/* We aren't ask to do anything ... */
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if (!(pfn_req_flags & HMM_PFN_REQ_FAULT))
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return 0;
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/* Need to write fault ? */
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if ((pfn_req_flags & HMM_PFN_REQ_WRITE) &&
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!(cpu_flags & HMM_PFN_WRITE))
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return HMM_NEED_FAULT | HMM_NEED_WRITE_FAULT;
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/* If CPU page table is not valid then we need to fault */
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if (!(cpu_flags & HMM_PFN_VALID))
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return HMM_NEED_FAULT;
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return 0;
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}
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static unsigned int
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hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
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const unsigned long hmm_pfns[], unsigned long npages,
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unsigned long cpu_flags)
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{
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struct hmm_range *range = hmm_vma_walk->range;
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unsigned int required_fault = 0;
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unsigned long i;
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/*
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* If the default flags do not request to fault pages, and the mask does
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* not allow for individual pages to be faulted, then
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* hmm_pte_need_fault() will always return 0.
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*/
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if (!((range->default_flags | range->pfn_flags_mask) &
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HMM_PFN_REQ_FAULT))
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return 0;
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for (i = 0; i < npages; ++i) {
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required_fault |= hmm_pte_need_fault(hmm_vma_walk, hmm_pfns[i],
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cpu_flags);
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if (required_fault == HMM_NEED_ALL_BITS)
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return required_fault;
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}
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return required_fault;
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}
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static int hmm_vma_walk_hole(unsigned long addr, unsigned long end,
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__always_unused int depth, struct mm_walk *walk)
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{
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struct hmm_vma_walk *hmm_vma_walk = walk->private;
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struct hmm_range *range = hmm_vma_walk->range;
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unsigned int required_fault;
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unsigned long i, npages;
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unsigned long *hmm_pfns;
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i = (addr - range->start) >> PAGE_SHIFT;
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npages = (end - addr) >> PAGE_SHIFT;
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hmm_pfns = &range->hmm_pfns[i];
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required_fault =
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hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0);
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if (!walk->vma) {
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if (required_fault)
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return -EFAULT;
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return hmm_pfns_fill(addr, end, range, HMM_PFN_ERROR);
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}
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if (required_fault)
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return hmm_vma_fault(addr, end, required_fault, walk);
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return hmm_pfns_fill(addr, end, range, 0);
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}
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static inline unsigned long hmm_pfn_flags_order(unsigned long order)
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{
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return order << HMM_PFN_ORDER_SHIFT;
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}
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static inline unsigned long pmd_to_hmm_pfn_flags(struct hmm_range *range,
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pmd_t pmd)
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{
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if (pmd_protnone(pmd))
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return 0;
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return (pmd_write(pmd) ? (HMM_PFN_VALID | HMM_PFN_WRITE) :
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HMM_PFN_VALID) |
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hmm_pfn_flags_order(PMD_SHIFT - PAGE_SHIFT);
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}
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#ifdef CONFIG_TRANSPARENT_HUGEPAGE
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static int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
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unsigned long end, unsigned long hmm_pfns[],
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pmd_t pmd)
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{
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struct hmm_vma_walk *hmm_vma_walk = walk->private;
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struct hmm_range *range = hmm_vma_walk->range;
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unsigned long pfn, npages, i;
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unsigned int required_fault;
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unsigned long cpu_flags;
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npages = (end - addr) >> PAGE_SHIFT;
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cpu_flags = pmd_to_hmm_pfn_flags(range, pmd);
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required_fault =
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hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, cpu_flags);
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if (required_fault)
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return hmm_vma_fault(addr, end, required_fault, walk);
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pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
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for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++)
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hmm_pfns[i] = pfn | cpu_flags;
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return 0;
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}
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#else /* CONFIG_TRANSPARENT_HUGEPAGE */
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/* stub to allow the code below to compile */
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int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
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unsigned long end, unsigned long hmm_pfns[], pmd_t pmd);
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#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
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static inline bool hmm_is_device_private_entry(struct hmm_range *range,
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swp_entry_t entry)
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{
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return is_device_private_entry(entry) &&
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device_private_entry_to_page(entry)->pgmap->owner ==
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range->dev_private_owner;
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}
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static inline unsigned long pte_to_hmm_pfn_flags(struct hmm_range *range,
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pte_t pte)
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{
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if (pte_none(pte) || !pte_present(pte) || pte_protnone(pte))
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return 0;
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return pte_write(pte) ? (HMM_PFN_VALID | HMM_PFN_WRITE) : HMM_PFN_VALID;
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}
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static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
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unsigned long end, pmd_t *pmdp, pte_t *ptep,
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unsigned long *hmm_pfn)
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{
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struct hmm_vma_walk *hmm_vma_walk = walk->private;
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struct hmm_range *range = hmm_vma_walk->range;
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unsigned int required_fault;
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unsigned long cpu_flags;
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pte_t pte = *ptep;
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uint64_t pfn_req_flags = *hmm_pfn;
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if (pte_none(pte)) {
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required_fault =
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hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0);
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if (required_fault)
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goto fault;
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*hmm_pfn = 0;
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return 0;
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}
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if (!pte_present(pte)) {
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swp_entry_t entry = pte_to_swp_entry(pte);
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/*
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* Never fault in device private pages, but just report
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* the PFN even if not present.
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*/
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if (hmm_is_device_private_entry(range, entry)) {
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cpu_flags = HMM_PFN_VALID;
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if (is_write_device_private_entry(entry))
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cpu_flags |= HMM_PFN_WRITE;
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*hmm_pfn = device_private_entry_to_pfn(entry) |
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cpu_flags;
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return 0;
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}
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required_fault =
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hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0);
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if (!required_fault) {
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*hmm_pfn = 0;
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return 0;
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}
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if (!non_swap_entry(entry))
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goto fault;
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if (is_migration_entry(entry)) {
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pte_unmap(ptep);
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hmm_vma_walk->last = addr;
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migration_entry_wait(walk->mm, pmdp, addr);
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return -EBUSY;
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}
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/* Report error for everything else */
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pte_unmap(ptep);
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return -EFAULT;
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}
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cpu_flags = pte_to_hmm_pfn_flags(range, pte);
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required_fault =
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hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, cpu_flags);
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if (required_fault)
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goto fault;
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/*
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* Since each architecture defines a struct page for the zero page, just
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* fall through and treat it like a normal page.
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*/
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if (pte_special(pte) && !is_zero_pfn(pte_pfn(pte))) {
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if (hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0)) {
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pte_unmap(ptep);
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return -EFAULT;
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}
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*hmm_pfn = HMM_PFN_ERROR;
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return 0;
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}
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*hmm_pfn = pte_pfn(pte) | cpu_flags;
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return 0;
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fault:
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pte_unmap(ptep);
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/* Fault any virtual address we were asked to fault */
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return hmm_vma_fault(addr, end, required_fault, walk);
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}
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static int hmm_vma_walk_pmd(pmd_t *pmdp,
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unsigned long start,
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unsigned long end,
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struct mm_walk *walk)
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{
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struct hmm_vma_walk *hmm_vma_walk = walk->private;
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struct hmm_range *range = hmm_vma_walk->range;
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unsigned long *hmm_pfns =
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&range->hmm_pfns[(start - range->start) >> PAGE_SHIFT];
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unsigned long npages = (end - start) >> PAGE_SHIFT;
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unsigned long addr = start;
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pte_t *ptep;
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pmd_t pmd;
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again:
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pmd = READ_ONCE(*pmdp);
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if (pmd_none(pmd))
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return hmm_vma_walk_hole(start, end, -1, walk);
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if (thp_migration_supported() && is_pmd_migration_entry(pmd)) {
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if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0)) {
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hmm_vma_walk->last = addr;
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pmd_migration_entry_wait(walk->mm, pmdp);
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return -EBUSY;
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}
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return hmm_pfns_fill(start, end, range, 0);
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}
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if (!pmd_present(pmd)) {
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if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0))
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return -EFAULT;
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return hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
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}
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if (pmd_devmap(pmd) || pmd_trans_huge(pmd)) {
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/*
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* No need to take pmd_lock here, even if some other thread
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* is splitting the huge pmd we will get that event through
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* mmu_notifier callback.
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*
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* So just read pmd value and check again it's a transparent
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* huge or device mapping one and compute corresponding pfn
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* values.
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*/
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pmd = pmd_read_atomic(pmdp);
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barrier();
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if (!pmd_devmap(pmd) && !pmd_trans_huge(pmd))
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goto again;
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return hmm_vma_handle_pmd(walk, addr, end, hmm_pfns, pmd);
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}
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/*
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* We have handled all the valid cases above ie either none, migration,
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* huge or transparent huge. At this point either it is a valid pmd
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* entry pointing to pte directory or it is a bad pmd that will not
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* recover.
|
|
*/
|
|
if (pmd_bad(pmd)) {
|
|
if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0))
|
|
return -EFAULT;
|
|
return hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
|
|
}
|
|
|
|
ptep = pte_offset_map(pmdp, addr);
|
|
for (; addr < end; addr += PAGE_SIZE, ptep++, hmm_pfns++) {
|
|
int r;
|
|
|
|
r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, hmm_pfns);
|
|
if (r) {
|
|
/* hmm_vma_handle_pte() did pte_unmap() */
|
|
return r;
|
|
}
|
|
}
|
|
pte_unmap(ptep - 1);
|
|
return 0;
|
|
}
|
|
|
|
#if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && \
|
|
defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)
|
|
static inline unsigned long pud_to_hmm_pfn_flags(struct hmm_range *range,
|
|
pud_t pud)
|
|
{
|
|
if (!pud_present(pud))
|
|
return 0;
|
|
return (pud_write(pud) ? (HMM_PFN_VALID | HMM_PFN_WRITE) :
|
|
HMM_PFN_VALID) |
|
|
hmm_pfn_flags_order(PUD_SHIFT - PAGE_SHIFT);
|
|
}
|
|
|
|
static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
|
|
struct mm_walk *walk)
|
|
{
|
|
struct hmm_vma_walk *hmm_vma_walk = walk->private;
|
|
struct hmm_range *range = hmm_vma_walk->range;
|
|
unsigned long addr = start;
|
|
pud_t pud;
|
|
int ret = 0;
|
|
spinlock_t *ptl = pud_trans_huge_lock(pudp, walk->vma);
|
|
|
|
if (!ptl)
|
|
return 0;
|
|
|
|
/* Normally we don't want to split the huge page */
|
|
walk->action = ACTION_CONTINUE;
|
|
|
|
pud = READ_ONCE(*pudp);
|
|
if (pud_none(pud)) {
|
|
spin_unlock(ptl);
|
|
return hmm_vma_walk_hole(start, end, -1, walk);
|
|
}
|
|
|
|
if (pud_huge(pud) && pud_devmap(pud)) {
|
|
unsigned long i, npages, pfn;
|
|
unsigned int required_fault;
|
|
unsigned long *hmm_pfns;
|
|
unsigned long cpu_flags;
|
|
|
|
if (!pud_present(pud)) {
|
|
spin_unlock(ptl);
|
|
return hmm_vma_walk_hole(start, end, -1, walk);
|
|
}
|
|
|
|
i = (addr - range->start) >> PAGE_SHIFT;
|
|
npages = (end - addr) >> PAGE_SHIFT;
|
|
hmm_pfns = &range->hmm_pfns[i];
|
|
|
|
cpu_flags = pud_to_hmm_pfn_flags(range, pud);
|
|
required_fault = hmm_range_need_fault(hmm_vma_walk, hmm_pfns,
|
|
npages, cpu_flags);
|
|
if (required_fault) {
|
|
spin_unlock(ptl);
|
|
return hmm_vma_fault(addr, end, required_fault, walk);
|
|
}
|
|
|
|
pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
|
|
for (i = 0; i < npages; ++i, ++pfn)
|
|
hmm_pfns[i] = pfn | cpu_flags;
|
|
goto out_unlock;
|
|
}
|
|
|
|
/* Ask for the PUD to be split */
|
|
walk->action = ACTION_SUBTREE;
|
|
|
|
out_unlock:
|
|
spin_unlock(ptl);
|
|
return ret;
|
|
}
|
|
#else
|
|
#define hmm_vma_walk_pud NULL
|
|
#endif
|
|
|
|
#ifdef CONFIG_HUGETLB_PAGE
|
|
static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
|
|
unsigned long start, unsigned long end,
|
|
struct mm_walk *walk)
|
|
{
|
|
unsigned long addr = start, i, pfn;
|
|
struct hmm_vma_walk *hmm_vma_walk = walk->private;
|
|
struct hmm_range *range = hmm_vma_walk->range;
|
|
struct vm_area_struct *vma = walk->vma;
|
|
unsigned int required_fault;
|
|
unsigned long pfn_req_flags;
|
|
unsigned long cpu_flags;
|
|
spinlock_t *ptl;
|
|
pte_t entry;
|
|
|
|
ptl = huge_pte_lock(hstate_vma(vma), walk->mm, pte);
|
|
entry = huge_ptep_get(pte);
|
|
|
|
i = (start - range->start) >> PAGE_SHIFT;
|
|
pfn_req_flags = range->hmm_pfns[i];
|
|
cpu_flags = pte_to_hmm_pfn_flags(range, entry) |
|
|
hmm_pfn_flags_order(huge_page_order(hstate_vma(vma)));
|
|
required_fault =
|
|
hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, cpu_flags);
|
|
if (required_fault) {
|
|
spin_unlock(ptl);
|
|
return hmm_vma_fault(addr, end, required_fault, walk);
|
|
}
|
|
|
|
pfn = pte_pfn(entry) + ((start & ~hmask) >> PAGE_SHIFT);
|
|
for (; addr < end; addr += PAGE_SIZE, i++, pfn++)
|
|
range->hmm_pfns[i] = pfn | cpu_flags;
|
|
|
|
spin_unlock(ptl);
|
|
return 0;
|
|
}
|
|
#else
|
|
#define hmm_vma_walk_hugetlb_entry NULL
|
|
#endif /* CONFIG_HUGETLB_PAGE */
|
|
|
|
static int hmm_vma_walk_test(unsigned long start, unsigned long end,
|
|
struct mm_walk *walk)
|
|
{
|
|
struct hmm_vma_walk *hmm_vma_walk = walk->private;
|
|
struct hmm_range *range = hmm_vma_walk->range;
|
|
struct vm_area_struct *vma = walk->vma;
|
|
|
|
if (!(vma->vm_flags & (VM_IO | VM_PFNMAP | VM_MIXEDMAP)) &&
|
|
vma->vm_flags & VM_READ)
|
|
return 0;
|
|
|
|
/*
|
|
* vma ranges that don't have struct page backing them or map I/O
|
|
* devices directly cannot be handled by hmm_range_fault().
|
|
*
|
|
* If the vma does not allow read access, then assume that it does not
|
|
* allow write access either. HMM does not support architectures that
|
|
* allow write without read.
|
|
*
|
|
* If a fault is requested for an unsupported range then it is a hard
|
|
* failure.
|
|
*/
|
|
if (hmm_range_need_fault(hmm_vma_walk,
|
|
range->hmm_pfns +
|
|
((start - range->start) >> PAGE_SHIFT),
|
|
(end - start) >> PAGE_SHIFT, 0))
|
|
return -EFAULT;
|
|
|
|
hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
|
|
|
|
/* Skip this vma and continue processing the next vma. */
|
|
return 1;
|
|
}
|
|
|
|
static const struct mm_walk_ops hmm_walk_ops = {
|
|
.pud_entry = hmm_vma_walk_pud,
|
|
.pmd_entry = hmm_vma_walk_pmd,
|
|
.pte_hole = hmm_vma_walk_hole,
|
|
.hugetlb_entry = hmm_vma_walk_hugetlb_entry,
|
|
.test_walk = hmm_vma_walk_test,
|
|
};
|
|
|
|
/**
|
|
* hmm_range_fault - try to fault some address in a virtual address range
|
|
* @range: argument structure
|
|
*
|
|
* Returns 0 on success or one of the following error codes:
|
|
*
|
|
* -EINVAL: Invalid arguments or mm or virtual address is in an invalid vma
|
|
* (e.g., device file vma).
|
|
* -ENOMEM: Out of memory.
|
|
* -EPERM: Invalid permission (e.g., asking for write and range is read
|
|
* only).
|
|
* -EBUSY: The range has been invalidated and the caller needs to wait for
|
|
* the invalidation to finish.
|
|
* -EFAULT: A page was requested to be valid and could not be made valid
|
|
* ie it has no backing VMA or it is illegal to access
|
|
*
|
|
* This is similar to get_user_pages(), except that it can read the page tables
|
|
* without mutating them (ie causing faults).
|
|
*/
|
|
int hmm_range_fault(struct hmm_range *range)
|
|
{
|
|
struct hmm_vma_walk hmm_vma_walk = {
|
|
.range = range,
|
|
.last = range->start,
|
|
};
|
|
struct mm_struct *mm = range->notifier->mm;
|
|
int ret;
|
|
|
|
mmap_assert_locked(mm);
|
|
|
|
do {
|
|
/* If range is no longer valid force retry. */
|
|
if (mmu_interval_check_retry(range->notifier,
|
|
range->notifier_seq))
|
|
return -EBUSY;
|
|
ret = walk_page_range(mm, hmm_vma_walk.last, range->end,
|
|
&hmm_walk_ops, &hmm_vma_walk);
|
|
/*
|
|
* When -EBUSY is returned the loop restarts with
|
|
* hmm_vma_walk.last set to an address that has not been stored
|
|
* in pfns. All entries < last in the pfn array are set to their
|
|
* output, and all >= are still at their input values.
|
|
*/
|
|
} while (ret == -EBUSY);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(hmm_range_fault);
|