From: Alistair Popple <apopple@xxxxxxxxxx> Subject: mm/hmm.c: allow VM_MIXEDMAP to work with hmm_range_fault hmm_range_fault() can be used instead of get_user_pages() for devices which allow faulting however unlike get_user_pages() it will return an error when used on a VM_MIXEDMAP range. To make hmm_range_fault() more closely match get_user_pages() remove this restriction. This requires dealing with the !ARCH_HAS_PTE_SPECIAL case in hmm_vma_handle_pte(). Rather than replicating the logic of vm_normal_page() call it directly and do a check for the zero pfn similar to what get_user_pages() currently does. Also add a test to hmm selftest to verify functionality. Link: https://lkml.kernel.org/r/20211104012001.2555676-1-apopple@xxxxxxxxxx Fixes: da4c3c735ea4 ("mm/hmm/mirror: helper to snapshot CPU page table") Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx> Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx> Cc: Jerome Glisse <jglisse@xxxxxxxxxx> Cc: John Hubbard <jhubbard@xxxxxxxxxx> Cc: Zi Yan <ziy@xxxxxxxxxx> Cc: Ralph Campbell <rcampbell@xxxxxxxxxx> Cc: Felix Kuehling <Felix.Kuehling@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- lib/test_hmm.c | 24 +++++++++++++ mm/hmm.c | 5 +- tools/testing/selftests/vm/hmm-tests.c | 42 +++++++++++++++++++++++ 3 files changed, 69 insertions(+), 2 deletions(-) --- a/lib/test_hmm.c~mm-hmmc-allow-vm_mixedmap-to-work-with-hmm_range_fault +++ a/lib/test_hmm.c @@ -1086,9 +1086,33 @@ static long dmirror_fops_unlocked_ioctl( return 0; } +static int dmirror_fops_mmap(struct file *file, struct vm_area_struct *vma) +{ + unsigned long addr; + + for (addr = vma->vm_start; addr < vma->vm_end; addr += PAGE_SIZE) { + struct page *page; + int ret; + + page = alloc_page(GFP_KERNEL | __GFP_ZERO); + if (!page) + return -ENOMEM; + + ret = vm_insert_page(vma, addr, page); + if (ret) { + __free_page(page); + return ret; + } + put_page(page); + } + + return 0; +} + static const struct file_operations dmirror_fops = { .open = dmirror_fops_open, .release = dmirror_fops_release, + .mmap = dmirror_fops_mmap, .unlocked_ioctl = dmirror_fops_unlocked_ioctl, .llseek = default_llseek, .owner = THIS_MODULE, --- a/mm/hmm.c~mm-hmmc-allow-vm_mixedmap-to-work-with-hmm_range_fault +++ a/mm/hmm.c @@ -300,7 +300,8 @@ static int hmm_vma_handle_pte(struct mm_ * Since each architecture defines a struct page for the zero page, just * fall through and treat it like a normal page. */ - if (pte_special(pte) && !pte_devmap(pte) && + if (!vm_normal_page(walk->vma, addr, pte) && + !pte_devmap(pte) && !is_zero_pfn(pte_pfn(pte))) { if (hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0)) { pte_unmap(ptep); @@ -518,7 +519,7 @@ static int hmm_vma_walk_test(unsigned lo 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)) && + if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)) && vma->vm_flags & VM_READ) return 0; --- a/tools/testing/selftests/vm/hmm-tests.c~mm-hmmc-allow-vm_mixedmap-to-work-with-hmm_range_fault +++ a/tools/testing/selftests/vm/hmm-tests.c @@ -1251,6 +1251,48 @@ TEST_F(hmm, anon_teardown) /* * Test memory snapshot without faulting in pages accessed by the device. */ +TEST_F(hmm, mixedmap) +{ + struct hmm_buffer *buffer; + unsigned long npages; + unsigned long size; + unsigned char *m; + int ret; + + npages = 1; + size = npages << self->page_shift; + + buffer = malloc(sizeof(*buffer)); + ASSERT_NE(buffer, NULL); + + buffer->fd = -1; + buffer->size = size; + buffer->mirror = malloc(npages); + ASSERT_NE(buffer->mirror, NULL); + + + /* Reserve a range of addresses. */ + buffer->ptr = mmap(NULL, size, + PROT_READ | PROT_WRITE, + MAP_PRIVATE, + self->fd, 0); + ASSERT_NE(buffer->ptr, MAP_FAILED); + + /* Simulate a device snapshotting CPU pagetables. */ + ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_SNAPSHOT, buffer, npages); + ASSERT_EQ(ret, 0); + ASSERT_EQ(buffer->cpages, npages); + + /* Check what the device saw. */ + m = buffer->mirror; + ASSERT_EQ(m[0], HMM_DMIRROR_PROT_READ); + + hmm_buffer_free(buffer); +} + +/* + * Test memory snapshot without faulting in pages accessed by the device. + */ TEST_F(hmm2, snapshot) { struct hmm_buffer *buffer; _
