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Presumably the intent here was that hmm_range_fault() could put the data into some HW specific format and thus avoid some work. However, nothing actually does that, and it isn't clear how anything actually could do that as hmm_range_fault() provides CPU addresses which must be DMA mapped. Perhaps there is some special HW that does not need DMA mapping, but we don't have any examples of this, and the theoretical performance win of avoiding an extra scan over the pfns array doesn't seem worth the complexity. Plus pfns needs to be scanned anyhow to sort out any DEVICE_PRIVATE pages. This version replaces the uint64_t with an usigned long containing a pfn and fixed flags. On input flags is filled with the HMM_PFN_REQ_* values, on successful output it is filled with HMM_PFN_* values, describing the state of the pages. amdgpu is simple to convert, it doesn't use snapshot and doesn't use per-page flags. nouveau uses only 16 hmm_pte entries at most (ie fits in a few cache lines), and it sweeps over its pfns array a couple of times anyhow. It also has a nasty call chain before it reaches the dma map and hardware suggesting performance isn't important: nouveau_svm_fault(): args.i.m.method = NVIF_VMM_V0_PFNMAP nouveau_range_fault() nvif_object_ioctl() client->driver->ioctl() struct nvif_driver nvif_driver_nvkm: .ioctl = nvkm_client_ioctl nvkm_ioctl() nvkm_ioctl_path() nvkm_ioctl_v0[type].func(..) nvkm_ioctl_mthd() nvkm_object_mthd() struct nvkm_object_func nvkm_uvmm: .mthd = nvkm_uvmm_mthd nvkm_uvmm_mthd() nvkm_uvmm_mthd_pfnmap() nvkm_vmm_pfn_map() nvkm_vmm_ptes_get_map() func == gp100_vmm_pgt_pfn struct nvkm_vmm_desc_func gp100_vmm_desc_spt: .pfn = gp100_vmm_pgt_pfn nvkm_vmm_iter() REF_PTES == func == gp100_vmm_pgt_pfn() dma_map_page() Link: https://lore.kernel.org/r/5-v2-b4e84f444c7d+24f57-hmm_no_flags_jgg@mellanox.com Acked-by: Felix Kuehling <Felix.Kuehling@amd.com> Tested-by: Ralph Campbell <rcampbell@nvidia.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
584 lines
16 KiB
C
584 lines
16 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) & 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 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) : HMM_PFN_VALID;
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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 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.
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*/
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if (pmd_bad(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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ptep = pte_offset_map(pmdp, addr);
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for (; addr < end; addr += PAGE_SIZE, ptep++, hmm_pfns++) {
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int r;
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r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, hmm_pfns);
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if (r) {
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/* hmm_vma_handle_pte() did pte_unmap() */
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return r;
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}
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}
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pte_unmap(ptep - 1);
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return 0;
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}
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#if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && \
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defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)
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static inline unsigned long pud_to_hmm_pfn_flags(struct hmm_range *range,
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pud_t pud)
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{
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if (!pud_present(pud))
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return 0;
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return pud_write(pud) ? (HMM_PFN_VALID | HMM_PFN_WRITE) : HMM_PFN_VALID;
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}
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static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, 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 addr = start;
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pud_t pud;
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int ret = 0;
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spinlock_t *ptl = pud_trans_huge_lock(pudp, walk->vma);
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if (!ptl)
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return 0;
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/* Normally we don't want to split the huge page */
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walk->action = ACTION_CONTINUE;
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pud = READ_ONCE(*pudp);
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if (pud_none(pud)) {
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spin_unlock(ptl);
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return hmm_vma_walk_hole(start, end, -1, walk);
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}
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if (pud_huge(pud) && pud_devmap(pud)) {
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unsigned long i, npages, pfn;
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unsigned int required_fault;
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unsigned long *hmm_pfns;
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unsigned long cpu_flags;
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if (!pud_present(pud)) {
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spin_unlock(ptl);
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return hmm_vma_walk_hole(start, end, -1, walk);
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}
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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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cpu_flags = pud_to_hmm_pfn_flags(range, pud);
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required_fault = hmm_range_need_fault(hmm_vma_walk, hmm_pfns,
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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);
|
|
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;
|
|
|
|
lockdep_assert_held(&mm->mmap_sem);
|
|
|
|
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);
|