On Mon, 10 Feb 2020 16:15:30 -0800 John Hubbard <jhubbard@xxxxxxxxxx> wrote: > Add tracking of pages that were pinned via FOLL_PIN. This tracking is > implemented via overloading of page->_refcount: pins are added by > adding GUP_PIN_COUNTING_BIAS (1024) to the refcount. This provides a > fuzzy indication of pinning, and it can have false positives (and that's > OK). Please see the pre-existing > Documentation/core-api/pin_user_pages.rst for details. > > As mentioned in pin_user_pages.rst, callers who effectively set FOLL_PIN > (typically via pin_user_pages*()) are required to ultimately free such > pages via unpin_user_page(). > > Please also note the limitation, discussed in pin_user_pages.rst under > the "TODO: for 1GB and larger huge pages" section. (That limitation will > be removed in a following patch.) > > The effect of a FOLL_PIN flag is similar to that of FOLL_GET, and may be > thought of as "FOLL_GET for DIO and/or RDMA use". > > Pages that have been pinned via FOLL_PIN are identifiable via a > new function call: > > bool page_maybe_dma_pinned(struct page *page); > > What to do in response to encountering such a page, is left to later > patchsets. There is discussion about this in [1], [2], [3], and [4]. > > This also changes a BUG_ON(), to a WARN_ON(), in follow_page_mask(). > > [1] Some slow progress on get_user_pages() (Apr 2, 2019): > https://lwn.net/Articles/784574/ > [2] DMA and get_user_pages() (LPC: Dec 12, 2018): > https://lwn.net/Articles/774411/ > [3] The trouble with get_user_pages() (Apr 30, 2018): > https://lwn.net/Articles/753027/ > [4] LWN kernel index: get_user_pages(): > https://lwn.net/Kernel/Index/#Memory_management-get_user_pages > > Reviewed-by: Jan Kara <jack@xxxxxxx> > Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > Suggested-by: Jan Kara <jack@xxxxxxx> > Suggested-by: Jérôme Glisse <jglisse@xxxxxxxxxx> > Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx> > --- > Documentation/core-api/pin_user_pages.rst | 6 +- > include/linux/mm.h | 82 +++++-- > mm/gup.c | 254 +++++++++++++++++----- > mm/huge_memory.c | 29 ++- > mm/hugetlb.c | 54 +++-- > 5 files changed, 334 insertions(+), 91 deletions(-) Hi John, I'm seeing a regression bisected back to this commit (3faa52c03f44 mm/gup: track FOLL_PIN pages). I've attached some vfio-pci test code that reproduces this by mmap'ing a page of MMIO space of a device and then tries to map that through the IOMMU, so this should be attempting a gup/pin of a PFNMAP page. Previously this failed gracefully (-EFAULT), but now results in: BUG: unable to handle page fault for address: ffffae5cbfe5e938 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] SMP NOPTI CPU: 18 PID: 3365 Comm: vfio-pci-dma-ma Tainted: G OE 5.6.0+ #6 Hardware name: AMD Corporation Diesel/Diesel, BIOS TDL100CB 03/17/2020 RIP: 0010:get_pfnblock_flags_mask+0x22/0x70 Code: c3 0f 1f 80 00 00 00 00 0f 1f 44 00 00 48 8b 05 bc e1 d9 01 48 89 f7 49 89 c8 48 c1 ef 0f 48 85 c0 74 48 48 89 f1 48 c1 e9 17 <48> 8b 04 c8 48 85 c0 74 0b 40 0f b6 ff 48 c1 e7 04 48 01 f8 48 c1 RSP: 0018:ffffb55289b3fcc8 EFLAGS: 00010216 RAX: ffff9e5cbff50000 RBX: 0000000000000001 RCX: 000001fffffe1d27 RDX: 0000000000000002 RSI: ffffff0e93acd633 RDI: 0001fffffe1d2759 RBP: ffffb55289b3fd88 R08: 0000000000000007 R09: ffff9e48a52476a8 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001 R13: 0000000000000000 R14: 0000000000000001 R15: ffff9e48ab358cc0 FS: 00007f4ef7269740(0000) GS:ffff9e48afa80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffae5cbfe5e938 CR3: 0000000c61eda000 CR4: 00000000003406e0 Call Trace: __gup_longterm_locked+0x274/0x620 vaddr_get_pfn+0x74/0x110 [vfio_iommu_type1] vfio_pin_pages_remote+0x6e/0x370 [vfio_iommu_type1] vfio_iommu_type1_ioctl+0x8e5/0xaac [vfio_iommu_type1] ksys_ioctl+0x86/0xc0 __x64_sys_ioctl+0x16/0x20 do_syscall_64+0x5b/0x1f0 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7f4ef6d7d307 Code: 44 00 00 48 8b 05 69 1b 2d 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 39 1b 2d 00 f7 d8 64 89 01 48 RSP: 002b:00007fff76ada738 EFLAGS: 00000213 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f4ef6d7d307 RDX: 00007fff76ada760 RSI: 0000000000003b71 RDI: 0000000000000003 RBP: 00007fff76ada930 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000213 R12: 0000000000400950 R13: 00007fff76adaa10 R14: 0000000000000000 R15: 0000000000000000 Modules linked in: vfio_pci(OE) vfio_virqfd(OE) vfio_iommu_type1(OE) vfio(OE) amd64_edac_mod edac_mce_amd kvm_amd kvm rfkill sunrpc ipmi_ssif vfat irqbypass fat ipmi_si crct10dif_pclmul crc32_pclmul sp5100_tco ghash_clmulni_intel ipmi_devintf pcspkr joydev ccp i2c_piix4 k10temp ipmi_msghandler pinctrl_amd acpi_cpufreq ip_tables nouveau ast video mxm_wmi drm_vram_helper wmi drm_ttm_helper i2c_algo_bit drm_kms_helper cec ttm drm i40e e1000e crc32c_intel CR2: ffffae5cbfe5e938 ---[ end trace a384ab7cc8e37d46 ]--- RIP: 0010:get_pfnblock_flags_mask+0x22/0x70 Code: c3 0f 1f 80 00 00 00 00 0f 1f 44 00 00 48 8b 05 bc e1 d9 01 48 89 f7 49 89 c8 48 c1 ef 0f 48 85 c0 74 48 48 89 f1 48 c1 e9 17 <48> 8b 04 c8 48 85 c0 74 0b 40 0f b6 ff 48 c1 e7 04 48 01 f8 48 c1 RSP: 0018:ffffb55289b3fcc8 EFLAGS: 00010216 RAX: ffff9e5cbff50000 RBX: 0000000000000001 RCX: 000001fffffe1d27 RDX: 0000000000000002 RSI: ffffff0e93acd633 RDI: 0001fffffe1d2759 RBP: ffffb55289b3fd88 R08: 0000000000000007 R09: ffff9e48a52476a8 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001 R13: 0000000000000000 R14: 0000000000000001 R15: ffff9e48ab358cc0 FS: 00007f4ef7269740(0000) GS:ffff9e48afa80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffae5cbfe5e938 CR3: 0000000c61eda000 CR4: 00000000003406e0 Thanks, Alex
#include <errno.h> #include <libgen.h> #include <fcntl.h> #include <signal.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/eventfd.h> #include <sys/ioctl.h> #include <sys/mman.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> #include <linux/ioctl.h> #include <linux/vfio.h> #include <linux/pci_regs.h> void usage(char *name) { fprintf(stderr, "usage: %s <ssss:bb:dd.f>\n", name); fprintf(stderr, "\tssss: PCI segment, ex. 0000\n"); fprintf(stderr, "\tbb: PCI bus, ex. 01\n"); fprintf(stderr, "\tdd: PCI device, ex. 06\n"); fprintf(stderr, "\tf: PCI function, ex. 0\n"); } int main(int argc, char **argv) { int seg, bus, slot, func; int ret, container, group, device, groupid; char path[50], iommu_group_path[50], *group_name; struct stat st; ssize_t len; void *map = MAP_FAILED; int i; unsigned int bar; struct vfio_group_status group_status = { .argsz = sizeof(group_status) }; struct vfio_region_info region_info = { .argsz = sizeof(region_info) }; struct vfio_region_info config_info = { .argsz = sizeof(config_info) }; struct vfio_iommu_type1_dma_map dma_map = { .argsz = sizeof(dma_map), .flags = VFIO_DMA_MAP_FLAG_READ | VFIO_DMA_MAP_FLAG_WRITE, }; if (argc != 2) { usage(argv[0]); return -1; } ret = sscanf(argv[1], "%04x:%02x:%02x.%d", &seg, &bus, &slot, &func); if (ret != 4) { fprintf(stderr, "Invalid device\n"); usage(argv[0]); return -1; } /* Boilerplate vfio setup */ container = open("/dev/vfio/vfio", O_RDWR); if (container < 0) { fprintf(stderr, "Failed to open /dev/vfio/vfio, %d (%s)\n", container, strerror(errno)); return container; } snprintf(path, sizeof(path), "/sys/bus/pci/devices/%04x:%02x:%02x.%01x/", seg, bus, slot, func); ret = stat(path, &st); if (ret < 0) { fprintf(stderr, "No such device\n"); return ret; } strncat(path, "iommu_group", sizeof(path) - strlen(path) - 1); len = readlink(path, iommu_group_path, sizeof(iommu_group_path)); if (len <= 0) { fprintf(stderr, "No iommu_group for device\n"); return -1; } iommu_group_path[len] = 0; group_name = basename(iommu_group_path); if (sscanf(group_name, "%d", &groupid) != 1) { fprintf(stderr, "Unknown group\n"); return -1; } snprintf(path, sizeof(path), "/dev/vfio/%d", groupid); group = open(path, O_RDWR); if (group < 0) { fprintf(stderr, "Failed to open %s, %d (%s)\n", path, group, strerror(errno)); return group; } ret = ioctl(group, VFIO_GROUP_GET_STATUS, &group_status); if (ret) { fprintf(stderr, "ioctl(VFIO_GROUP_GET_STATUS) failed\n"); return ret; } if (!(group_status.flags & VFIO_GROUP_FLAGS_VIABLE)) { fprintf(stderr, "Group not viable, all devices attached to vfio?\n"); return -1; } ret = ioctl(group, VFIO_GROUP_SET_CONTAINER, &container); if (ret) { fprintf(stderr, "Failed to set group container\n"); return ret; } ret = ioctl(container, VFIO_SET_IOMMU, VFIO_TYPE1_IOMMU); if (ret) { fprintf(stderr, "Failed to set IOMMU\n"); return ret; } snprintf(path, sizeof(path), "%04x:%02x:%02x.%d", seg, bus, slot, func); device = ioctl(group, VFIO_GROUP_GET_DEVICE_FD, path); if (device < 0) { fprintf(stderr, "Failed to get device\n"); return -ENODEV; } config_info.index = VFIO_PCI_CONFIG_REGION_INDEX; ret = ioctl(device, VFIO_DEVICE_GET_REGION_INFO, &config_info); if (ret) { fprintf(stderr, "Failed to get config space region info\n"); return ret; } for (i = 0; i < 6; i++) { if (pread(device, &bar, sizeof(bar), config_info.offset + PCI_BASE_ADDRESS_0 + (4 * i)) != sizeof(bar)) { fprintf(stderr, "Error reading BAR%d\n", i); return -errno; } if (!(bar & PCI_BASE_ADDRESS_SPACE)) { break; tryagain: if (bar & PCI_BASE_ADDRESS_MEM_TYPE_64) i++; } } if (i >= 6) { fprintf(stderr, "No memory BARs found\n"); return -ENODEV; } region_info.index = VFIO_PCI_BAR0_REGION_INDEX + i; ret = ioctl(device, VFIO_DEVICE_GET_REGION_INFO, ®ion_info); if (ret) { fprintf(stderr, "Failed to get BAR%d region info\n", i); return ret; } if (!(region_info.flags & VFIO_REGION_INFO_FLAG_MMAP)) { printf("No mmap support, try next\n"); goto tryagain; } if (region_info.size < getpagesize()) { printf("Too small for mmap, try next\n"); goto tryagain; } map = mmap(NULL, getpagesize(), PROT_READ | PROT_WRITE, MAP_SHARED, device, region_info.offset); if (map == MAP_FAILED) { fprintf(stderr, "Error mmap'ing BAR: %m\n"); goto tryagain; } dma_map.size = getpagesize(); dma_map.vaddr = (__u64)map; dma_map.iova = 1024 * 1024 * 1024; /* 1GB IOVA, arbitrary */ ret = ioctl(container, VFIO_IOMMU_MAP_DMA, &dma_map); if (ret) { fprintf(stderr, "Failed to DMA map: %m\n"); return ret; } printf("Passed\n"); return 0; }