[PATCH v8 1/3] mm/hmm/test: add selftest driver for HMM

Ralph Campbell
2020-03-21T00:31:19Z

This driver is for testing device private memory migration and devices
which use hmm_range_fault() to access system memory via device page tables.

Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
---
include/uapi/linux/test_hmm.h | 59 ++
lib/Kconfig.debug | 12 +
lib/Makefile | 1 +
lib/test_hmm.c | 1177 +++++++++++++++++++++++++++++++++
4 files changed, 1249 insertions(+)
create mode 100644 include/uapi/linux/test_hmm.h
create mode 100644 lib/test_hmm.c

diff --git a/include/uapi/linux/test_hmm.h b/include/uapi/linux/test_hmm.h
new file mode 100644
index 000000000000..8c5f70c160bf
--- /dev/null
+++ b/include/uapi/linux/test_hmm.h
@@ -0,0 +1,59 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * This is a module to test the HMM (Heterogeneous Memory Management) API
+ * of the kernel. It allows a userspace program to expose its entire address
+ * space through the HMM test module device file.
+ */
+#ifndef _UAPI_LINUX_HMM_DMIRROR_H
+#define _UAPI_LINUX_HMM_DMIRROR_H
+
+#include <linux/types.h>
+#include <linux/ioctl.h>
+
+/*
+ * Structure to pass to the HMM test driver to mimic a device accessing
+ * system memory and ZONE_DEVICE private memory through device page tables.
+ *
+ * @addr: (in) user address the device will read/write
+ * @ptr: (in) user address where device data is copied to/from
+ * @npages: (in) number of pages to read/write
+ * @cpages: (out) number of pages copied
+ * @faults: (out) number of device page faults seen
+ */
+struct hmm_dmirror_cmd {
+ __u64 addr;
+ __u64 ptr;
+ __u64 npages;
+ __u64 cpages;
+ __u64 faults;
+};
+
+/* Expose the address space of the calling process through hmm device file */
+#define HMM_DMIRROR_READ _IOWR('H', 0x00, struct hmm_dmirror_cmd)
+#define HMM_DMIRROR_WRITE _IOWR('H', 0x01, struct hmm_dmirror_cmd)
+#define HMM_DMIRROR_MIGRATE _IOWR('H', 0x02, struct hmm_dmirror_cmd)
+#define HMM_DMIRROR_SNAPSHOT _IOWR('H', 0x03, struct hmm_dmirror_cmd)
+
+/*
+ * Values returned in hmm_dmirror_cmd.ptr for HMM_DMIRROR_SNAPSHOT.
+ * HMM_DMIRROR_PROT_ERROR: no valid mirror PTE for this page
+ * HMM_DMIRROR_PROT_NONE: unpopulated PTE or PTE with no access
+ * HMM_DMIRROR_PROT_READ: read-only PTE
+ * HMM_DMIRROR_PROT_WRITE: read/write PTE
+ * HMM_DMIRROR_PROT_ZERO: special read-only zero page
+ * HMM_DMIRROR_PROT_DEV_PRIVATE_LOCAL: Migrated device private page on the
+ * device the ioctl() is made
+ * HMM_DMIRROR_PROT_DEV_PRIVATE_REMOTE: Migrated device private page on some
+ * other device
+ */
+enum {
+ HMM_DMIRROR_PROT_ERROR = 0xFF,
+ HMM_DMIRROR_PROT_NONE = 0x00,
+ HMM_DMIRROR_PROT_READ = 0x01,
+ HMM_DMIRROR_PROT_WRITE = 0x02,
+ HMM_DMIRROR_PROT_ZERO = 0x10,
+ HMM_DMIRROR_PROT_DEV_PRIVATE_LOCAL = 0x20,
+ HMM_DMIRROR_PROT_DEV_PRIVATE_REMOTE = 0x30,
+};
+
+#endif /* _UAPI_LINUX_HMM_DMIRROR_H */
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 69def4a9df00..f777e1215e33 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2162,6 +2162,18 @@ config TEST_MEMINIT

If unsure, say N.

+config TEST_HMM
+ tristate "Test HMM (Heterogeneous Memory Management)"
+ depends on DEVICE_PRIVATE
+ select HMM_MIRROR
+ select MMU_NOTIFIER
+ help
+ This is a pseudo device driver solely for testing HMM.
+ Say M here if you want to build the HMM test module.
+ Doing so will allow you to run tools/testing/selftest/vm/hmm-tests.
+
+ If unsure, say N.
+
endif # RUNTIME_TESTING_MENU

config MEMTEST
diff --git a/lib/Makefile b/lib/Makefile
index 611872c06926..c168bdc803dc 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -89,6 +89,7 @@ obj-$(CONFIG_TEST_OBJAGG) += test_objagg.o
obj-$(CONFIG_TEST_STACKINIT) += test_stackinit.o
obj-$(CONFIG_TEST_BLACKHOLE_DEV) += test_blackhole_dev.o
obj-$(CONFIG_TEST_MEMINIT) += test_meminit.o
+obj-$(CONFIG_TEST_HMM) += test_hmm.o

obj-$(CONFIG_TEST_LIVEPATCH) += livepatch/

diff --git a/lib/test_hmm.c b/lib/test_hmm.c
new file mode 100644
index 000000000000..d75e18f2ffd2
--- /dev/null
+++ b/lib/test_hmm.c
@@ -0,0 +1,1177 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * This is a module to test the HMM (Heterogeneous Memory Management)
+ * mirror and zone device private memory migration APIs of the kernel.
+ * Userspace programs can register with the driver to mirror their own address
+ * space and can use the device to read/write any valid virtual address.
+ */
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/cdev.h>
+#include <linux/device.h>
+#include <linux/mutex.h>
+#include <linux/rwsem.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/highmem.h>
+#include <linux/delay.h>
+#include <linux/pagemap.h>
+#include <linux/hmm.h>
+#include <linux/vmalloc.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+#include <linux/sched/mm.h>
+#include <linux/platform_device.h>
+
+#include <uapi/linux/test_hmm.h>
+
+#define DMIRROR_NDEVICES 2
+#define DMIRROR_RANGE_FAULT_TIMEOUT 1000
+#define DEVMEM_CHUNK_SIZE (256 * 1024 * 1024U)
+#define DEVMEM_CHUNKS_RESERVE 16
+
+static const struct dev_pagemap_ops dmirror_devmem_ops;
+static const struct mmu_interval_notifier_ops dmirror_min_ops;
+static dev_t dmirror_dev;
+static struct page *dmirror_zero_page;
+
+struct dmirror_device;
+
+struct dmirror_bounce {
+ void *ptr;
+ unsigned long size;
+ unsigned long addr;
+ unsigned long cpages;
+};
+
+#define DPT_SHIFT PAGE_SHIFT
+#define DPT_VALID (1UL << 0)
+#define DPT_WRITE (1UL << 1)
+
+#define DPT_XA_TAG_WRITE 3UL
+
+static const uint64_t dmirror_hmm_flags[HMM_PFN_FLAG_MAX] = {
+ [HMM_PFN_VALID] = DPT_VALID,
+ [HMM_PFN_WRITE] = DPT_WRITE,
+};
+
+static const uint64_t dmirror_hmm_values[HMM_PFN_VALUE_MAX] = {
+ [HMM_PFN_NONE] = 0,
+ [HMM_PFN_ERROR] = 0x10,
+ [HMM_PFN_SPECIAL] = 0x10,
+};
+
+/*
+ * Data structure to track address ranges and register for mmu interval
+ * notifier updates.
+ */
+struct dmirror_interval {
+ struct mmu_interval_notifier notifier;
+ struct dmirror *dmirror;
+};
+
+/*
+ * Data attached to the open device file.
+ * Note that it might be shared after a fork().
+ */
+struct dmirror {
+ struct dmirror_device *mdevice;
+ struct xarray pt;
+ struct mmu_interval_notifier notifier;
+ struct mutex mutex;
+};
+
+/*
+ * ZONE_DEVICE pages for migration and simulating device memory.
+ */
+struct dmirror_chunk {
+ struct dev_pagemap pagemap;
+ struct dmirror_device *mdevice;
+};
+
+/*
+ * Per device data.
+ */
+struct dmirror_device {
+ struct cdev cdevice;
+ struct hmm_devmem *devmem;
+
+ unsigned int devmem_capacity;
+ unsigned int devmem_count;
+ struct dmirror_chunk **devmem_chunks;
+ struct mutex devmem_lock; /* protects the above */
+
+ unsigned long calloc;
+ unsigned long cfree;
+ struct page *free_pages;
+ spinlock_t lock; /* protects the above */
+};
+
+static struct dmirror_device dmirror_devices[DMIRROR_NDEVICES];
+
+static int dmirror_bounce_init(struct dmirror_bounce *bounce,
+ unsigned long addr,
+ unsigned long size)
+{
+ bounce->addr = addr;
+ bounce->size = size;
+ bounce->cpages = 0;
+ bounce->ptr = vmalloc(size);
+ if (!bounce->ptr)
+ return -ENOMEM;
+ return 0;
+}
+
+static void dmirror_bounce_fini(struct dmirror_bounce *bounce)
+{
+ vfree(bounce->ptr);
+}
+
+static int dmirror_fops_open(struct inode *inode, struct file *filp)
+{
+ struct cdev *cdev = inode->i_cdev;
+ struct dmirror *dmirror;
+ int ret;
+
+ /* Mirror this process address space */
+ dmirror = kzalloc(sizeof(*dmirror), GFP_KERNEL);
+ if (dmirror == NULL)
+ return -ENOMEM;
+
+ dmirror->mdevice = container_of(cdev, struct dmirror_device, cdevice);
+ mutex_init(&dmirror->mutex);
+ xa_init(&dmirror->pt);
+
+ ret = mmu_interval_notifier_insert(&dmirror->notifier, current->mm,
+ 0, ULONG_MAX & PAGE_MASK, &dmirror_min_ops);
+ if (ret) {
+ kfree(dmirror);
+ return ret;
+ }
+
+ filp->private_data = dmirror;
+ return 0;
+}
+
+static int dmirror_fops_release(struct inode *inode, struct file *filp)
+{
+ struct dmirror *dmirror = filp->private_data;
+
+ mmu_interval_notifier_remove(&dmirror->notifier);
+ xa_destroy(&dmirror->pt);
+ kfree(dmirror);
+ return 0;
+}
+
+static inline struct dmirror_device *dmirror_page_to_device(struct page *page)
+
+{
+ return container_of(page->pgmap, struct dmirror_chunk,
+ pagemap)->mdevice;
+}
+
+static int dmirror_do_fault(struct dmirror *dmirror, struct hmm_range *range)
+{
+ uint64_t *pfns = range->pfns;
+ unsigned long pfn;
+
+ for (pfn = (range->start >> PAGE_SHIFT);
+ pfn < (range->end >> PAGE_SHIFT);
+ pfn++, pfns++) {
+ struct page *page;
+ void *entry;
+
+ /*
+ * Since we asked for hmm_range_fault() to populate pages,
+ * it shouldn't return an error entry on success.
+ */
+ WARN_ON(*pfns == range->values[HMM_PFN_ERROR]);
+
+ page = hmm_device_entry_to_page(range, *pfns);
+ WARN_ON(!page);
+
+ entry = page;
+ if (*pfns & range->flags[HMM_PFN_WRITE])
+ entry = xa_tag_pointer(entry, DPT_XA_TAG_WRITE);
+ else if (range->default_flags & range->flags[HMM_PFN_WRITE])
+ return -EFAULT;
+ entry = xa_store(&dmirror->pt, pfn, entry, GFP_ATOMIC);
+ if (xa_is_err(entry))
+ return xa_err(entry);
+ }
+
+ return 0;
+}
+
+static void dmirror_do_update(struct dmirror *dmirror, unsigned long start,
+ unsigned long end)
+{
+ unsigned long pfn;
+
+ /*
+ * The XArray doesn't hold references to pages since it relies on
+ * the mmu notifier to clear page pointers when they become stale.
+ * Therefore, it is OK to just clear the entry.
+ */
+ for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++)
+ xa_erase(&dmirror->pt, pfn);
+}
+
+static bool dmirror_interval_invalidate(struct mmu_interval_notifier *mni,
+ const struct mmu_notifier_range *range,
+ unsigned long cur_seq)
+{
+ struct dmirror *dmirror = container_of(mni, struct dmirror, notifier);
+
+ /*
+ * If everything is being invalidated, just return since the
+ * mmget_not_zero() will protect the device page table from
+ * being used if the file remains open after the process dies
+ * (e.g., dup() or fork()).
+ */
+ if (range->start == 0 && range->end == ULONG_MAX)
+ return true;
+
+ if (mmu_notifier_range_blockable(range))
+ mutex_lock(&dmirror->mutex);
+ else if (!mutex_trylock(&dmirror->mutex))
+ return false;
+
+ mmu_interval_set_seq(mni, cur_seq);
+ dmirror_do_update(dmirror, range->start, range->end);
+
+ mutex_unlock(&dmirror->mutex);
+ return true;
+}
+
+static const struct mmu_interval_notifier_ops dmirror_min_ops = {
+ .invalidate = dmirror_interval_invalidate,
+};
+
+static int dmirror_range_fault(struct dmirror *dmirror,
+ struct hmm_range *range)
+{
+ struct mm_struct *mm = dmirror->notifier.mm;
+ unsigned long timeout =
+ jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
+ int ret;
+
+ while (true) {
+ long count;
+
+ if (time_after(jiffies, timeout)) {
+ ret = -EBUSY;
+ goto out;
+ }
+
+ range->notifier_seq = mmu_interval_read_begin(range->notifier);
+ down_read(&mm->mmap_sem);
+ count = hmm_range_fault(range);
+ up_read(&mm->mmap_sem);
+ if (count <= 0) {
+ if (count == 0 || count == -EBUSY)
+ continue;
+ ret = count;
+ goto out;
+ }
+
+ mutex_lock(&dmirror->mutex);
+ if (mmu_interval_read_retry(range->notifier,
+ range->notifier_seq)) {
+ mutex_unlock(&dmirror->mutex);
+ continue;
+ }
+ break;
+ }
+
+ ret = dmirror_do_fault(dmirror, range);
+
+ mutex_unlock(&dmirror->mutex);
+out:
+ return ret;
+}
+
+static int dmirror_fault(struct dmirror *dmirror, unsigned long start,
+ unsigned long end, bool write)
+{
+ struct mm_struct *mm = dmirror->notifier.mm;
+ unsigned long addr;
+ uint64_t pfns[64];
+ struct hmm_range range = {
+ .notifier = &dmirror->notifier,
+ .pfns = pfns,
+ .flags = dmirror_hmm_flags,
+ .values = dmirror_hmm_values,
+ .pfn_shift = DPT_SHIFT,
+ .pfn_flags_mask = 0,
+ .default_flags = dmirror_hmm_flags[HMM_PFN_VALID] |
+ (write ? dmirror_hmm_flags[HMM_PFN_WRITE] : 0),
+ .dev_private_owner = dmirror->mdevice,
+ };
+ int ret = 0;
+
+ /* Since the mm is for the mirrored process, get a reference first. */
+ if (!mmget_not_zero(mm))
+ return 0;
+
+ for (addr = start; addr < end; addr = range.end) {
+ range.start = addr;
+ range.end = min(addr + (ARRAY_SIZE(pfns) << PAGE_SHIFT), end);
+
+ ret = dmirror_range_fault(dmirror, &range);
+ if (ret)
+ break;
+ }
+
+ mmput(mm);
+ return ret;
+}
+
+static int dmirror_do_read(struct dmirror *dmirror, unsigned long start,
+ unsigned long end, struct dmirror_bounce *bounce)
+{
+ unsigned long pfn;
+ void *ptr;
+
+ ptr = bounce->ptr + ((start - bounce->addr) & PAGE_MASK);
+
+ for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++) {
+ void *entry;
+ struct page *page;
+ void *tmp;
+
+ entry = xa_load(&dmirror->pt, pfn);
+ page = xa_untag_pointer(entry);
+ if (!page)
+ return -ENOENT;
+
+ tmp = kmap(page);
+ memcpy(ptr, tmp, PAGE_SIZE);
+ kunmap(page);
+
+ ptr += PAGE_SIZE;
+ bounce->cpages++;
+ }
+
+ return 0;
+}
+
+static int dmirror_read(struct dmirror *dmirror, struct hmm_dmirror_cmd *cmd)
+{
+ struct dmirror_bounce bounce;
+ unsigned long start, end;
+ unsigned long size = cmd->npages << PAGE_SHIFT;
+ int ret;
+
+ start = cmd->addr;
+ end = start + size;
+ if (end < start)
+ return -EINVAL;
+
+ ret = dmirror_bounce_init(&bounce, start, size);
+ if (ret)
+ return ret;
+
+ while (1) {
+ mutex_lock(&dmirror->mutex);
+ ret = dmirror_do_read(dmirror, start, end, &bounce);
+ mutex_unlock(&dmirror->mutex);
+ if (ret != -ENOENT)
+ break;
+
+ start = cmd->addr + (bounce.cpages << PAGE_SHIFT);
+ ret = dmirror_fault(dmirror, start, end, false);
+ if (ret)
+ break;
+ cmd->faults++;
+ }
+
+ if (ret == 0)
+ ret = copy_to_user(u64_to_user_ptr(cmd->ptr), bounce.ptr,
+ bounce.size);
+ cmd->cpages = bounce.cpages;
+ dmirror_bounce_fini(&bounce);
+ return ret;
+}
+
+static int dmirror_do_write(struct dmirror *dmirror, unsigned long start,
+ unsigned long end, struct dmirror_bounce *bounce)
+{
+ unsigned long pfn;
+ void *ptr;
+
+ ptr = bounce->ptr + ((start - bounce->addr) & PAGE_MASK);
+
+ for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++) {
+ void *entry;
+ struct page *page;
+ void *tmp;
+
+ entry = xa_load(&dmirror->pt, pfn);
+ page = xa_untag_pointer(entry);
+ if (!page || xa_pointer_tag(entry) != DPT_XA_TAG_WRITE)
+ return -ENOENT;
+
+ tmp = kmap(page);
+ memcpy(tmp, ptr, PAGE_SIZE);
+ kunmap(page);
+
+ ptr += PAGE_SIZE;
+ bounce->cpages++;
+ }
+
+ return 0;
+}
+
+static int dmirror_write(struct dmirror *dmirror, struct hmm_dmirror_cmd *cmd)
+{
+ struct dmirror_bounce bounce;
+ unsigned long start, end;
+ unsigned long size = cmd->npages << PAGE_SHIFT;
+ int ret;
+
+ start = cmd->addr;
+ end = start + size;
+ if (end < start)
+ return -EINVAL;
+
+ ret = dmirror_bounce_init(&bounce, start, size);
+ if (ret)
+ return ret;
+ ret = copy_from_user(bounce.ptr, u64_to_user_ptr(cmd->ptr),
+ bounce.size);
+ if (ret)
+ return ret;
+
+ while (1) {
+ mutex_lock(&dmirror->mutex);
+ ret = dmirror_do_write(dmirror, start, end, &bounce);
+ mutex_unlock(&dmirror->mutex);
+ if (ret != -ENOENT)
+ break;
+
+ start = cmd->addr + (bounce.cpages << PAGE_SHIFT);
+ ret = dmirror_fault(dmirror, start, end, true);
+ if (ret)
+ break;
+ cmd->faults++;
+ }
+
+ cmd->cpages = bounce.cpages;
+ dmirror_bounce_fini(&bounce);
+ return ret;
+}
+
+static bool dmirror_allocate_chunk(struct dmirror_device *mdevice,
+ struct page **ppage)
+{
+ struct dmirror_chunk *devmem;
+ struct resource *res;
+ unsigned long pfn;
+ unsigned long pfn_first;
+ unsigned long pfn_last;
+ void *ptr;
+
+ mutex_lock(&mdevice->devmem_lock);
+
+ if (mdevice->devmem_count == mdevice->devmem_capacity) {
+ struct dmirror_chunk **new_chunks;
+ unsigned int new_capacity;
+
+ new_capacity = mdevice->devmem_capacity +
+ DEVMEM_CHUNKS_RESERVE;
+ new_chunks = krealloc(mdevice->devmem_chunks,
+ sizeof(new_chunks[0]) * new_capacity,
+ GFP_KERNEL);
+ if (!new_chunks)
+ goto err;
+ mdevice->devmem_capacity = new_capacity;
+ mdevice->devmem_chunks = new_chunks;
+ }
+
+ res = request_free_mem_region(&iomem_resource, DEVMEM_CHUNK_SIZE,
+ "hmm_dmirror");
+ if (IS_ERR(res))
+ goto err;
+
+ devmem = kzalloc(sizeof(*devmem), GFP_KERNEL);
+ if (!devmem)
+ goto err;
+
+ devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
+ devmem->pagemap.res = *res;
+ devmem->pagemap.ops = &dmirror_devmem_ops;
+ devmem->pagemap.owner = mdevice;
+
+ ptr = memremap_pages(&devmem->pagemap, numa_node_id());
+ if (IS_ERR(ptr))
+ goto err_free;
+
+ devmem->mdevice = mdevice;
+ pfn_first = devmem->pagemap.res.start >> PAGE_SHIFT;
+ pfn_last = pfn_first +
+ (resource_size(&devmem->pagemap.res) >> PAGE_SHIFT);
+ mdevice->devmem_chunks[mdevice->devmem_count++] = devmem;
+
+ mutex_unlock(&mdevice->devmem_lock);
+
+ pr_info("added new %u MB chunk (total %u chunks, %u MB) PFNs [0x%lx 0x%lx)\n",
+ DEVMEM_CHUNK_SIZE / (1024 * 1024),
+ mdevice->devmem_count,
+ mdevice->devmem_count * (DEVMEM_CHUNK_SIZE / (1024 * 1024)),
+ pfn_first, pfn_last);
+
+ spin_lock(&mdevice->lock);
+ for (pfn = pfn_first; pfn < pfn_last; pfn++) {
+ struct page *page = pfn_to_page(pfn);
+
+ page->zone_device_data = mdevice->free_pages;
+ mdevice->free_pages = page;
+ }
+ if (ppage) {
+ *ppage = mdevice->free_pages;
+ mdevice->free_pages = (*ppage)->zone_device_data;
+ mdevice->calloc++;
+ }
+ spin_unlock(&mdevice->lock);
+
+ return true;
+
+err_free:
+ kfree(devmem);
+err:
+ mutex_unlock(&mdevice->devmem_lock);
+ return false;
+}
+
+static struct page *dmirror_devmem_alloc_page(struct dmirror_device *mdevice)
+{
+ struct page *dpage = NULL;
+ struct page *rpage;
+
+ /*
+ * This is a fake device so we alloc real system memory to store
+ * our device memory.
+ */
+ rpage = alloc_page(GFP_HIGHUSER);
+ if (!rpage)
+ return NULL;
+
+ spin_lock(&mdevice->lock);
+
+ if (mdevice->free_pages) {
+ dpage = mdevice->free_pages;
+ mdevice->free_pages = dpage->zone_device_data;
+ mdevice->calloc++;
+ spin_unlock(&mdevice->lock);
+ } else {
+ spin_unlock(&mdevice->lock);
+ if (!dmirror_allocate_chunk(mdevice, &dpage))
+ goto error;
+ }
+
+ dpage->zone_device_data = rpage;
+ get_page(dpage);
+ lock_page(dpage);
+ return dpage;
+
+error:
+ __free_page(rpage);
+ return NULL;
+}
+
+static void dmirror_migrate_alloc_and_copy(struct migrate_vma *args,
+ struct dmirror *dmirror)
+{
+ struct dmirror_device *mdevice = dmirror->mdevice;
+ const unsigned long *src = args->src;
+ unsigned long *dst = args->dst;
+ unsigned long addr;
+
+ for (addr = args->start; addr < args->end; addr += PAGE_SIZE,
+ src++, dst++) {
+ struct page *spage;
+ struct page *dpage;
+ struct page *rpage;
+
+ if (!(*src & MIGRATE_PFN_MIGRATE))
+ continue;
+
+ /*
+ * Note that spage might be NULL which is OK since it is an
+ * unallocated pte_none() or read-only zero page.
+ */
+ spage = migrate_pfn_to_page(*src);
+
+ /*
+ * Don't migrate device private pages from our own driver or
+ * others. For our own we would do a device private memory copy
+ * not a migration and for others, we would need to fault the
+ * other device's page into system memory first.
+ */
+ if (spage && is_zone_device_page(spage))
+ continue;
+
+ dpage = dmirror_devmem_alloc_page(mdevice);
+ if (!dpage)
+ continue;
+
+ rpage = dpage->zone_device_data;
+ if (spage)
+ copy_highpage(rpage, spage);
+ else
+ clear_highpage(rpage);
+
+ /*
+ * Normally, a device would use the page->zone_device_data to
+ * point to the mirror but here we use it to hold the page for
+ * the simulated device memory and that page holds the pointer
+ * to the mirror.
+ */
+ rpage->zone_device_data = dmirror;
+
+ *dst = migrate_pfn(page_to_pfn(dpage)) |
+ MIGRATE_PFN_LOCKED;
+ if ((*src & MIGRATE_PFN_WRITE) ||
+ (!spage && args->vma->vm_flags & VM_WRITE))
+ *dst |= MIGRATE_PFN_WRITE;
+ }
+}
+
+static int dmirror_migrate_finalize_and_map(struct migrate_vma *args,
+ struct dmirror *dmirror)
+{
+ unsigned long start = args->start;
+ unsigned long end = args->end;
+ const unsigned long *src = args->src;
+ const unsigned long *dst = args->dst;
+ unsigned long pfn;
+
+ /* Map the migrated pages into the device's page tables. */
+ mutex_lock(&dmirror->mutex);
+
+ for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++,
+ src++, dst++) {
+ struct page *dpage;
+ void *entry;
+
+ if (!(*src & MIGRATE_PFN_MIGRATE))
+ continue;
+
+ dpage = migrate_pfn_to_page(*dst);
+ if (!dpage)
+ continue;
+
+ /*
+ * Store the page that holds the data so the page table
+ * doesn't have to deal with ZONE_DEVICE private pages.
+ */
+ entry = dpage->zone_device_data;
+ if (*dst & MIGRATE_PFN_WRITE)
+ entry = xa_tag_pointer(entry, DPT_XA_TAG_WRITE);
+ entry = xa_store(&dmirror->pt, pfn, entry, GFP_ATOMIC);
+ if (xa_is_err(entry))
+ return xa_err(entry);
+ }
+
+ mutex_unlock(&dmirror->mutex);
+ return 0;
+}
+
+static int dmirror_migrate(struct dmirror *dmirror,
+ struct hmm_dmirror_cmd *cmd)
+{
+ unsigned long start, end, addr;
+ unsigned long size = cmd->npages << PAGE_SHIFT;
+ struct mm_struct *mm = dmirror->notifier.mm;
+ struct vm_area_struct *vma;
+ unsigned long src_pfns[64];
+ unsigned long dst_pfns[64];
+ struct dmirror_bounce bounce;
+ struct migrate_vma args;
+ unsigned long next;
+ int ret;
+
+ start = cmd->addr;
+ end = start + size;
+ if (end < start)
+ return -EINVAL;
+
+ /* Since the mm is for the mirrored process, get a reference first. */
+ if (!mmget_not_zero(mm))
+ return -EINVAL;
+
+ down_read(&mm->mmap_sem);
+ for (addr = start; addr < end; addr = next) {
+ vma = find_vma(mm, addr);
+ if (!vma || addr < vma->vm_start) {
+ ret = -EINVAL;
+ goto out;
+ }
+ next = min(end, addr + (ARRAY_SIZE(src_pfns) << PAGE_SHIFT));
+ if (next > vma->vm_end)
+ next = vma->vm_end;
+
+ args.vma = vma;
+ args.src = src_pfns;
+ args.dst = dst_pfns;
+ args.start = addr;
+ args.end = next;
+ args.src_owner = NULL;
+ ret = migrate_vma_setup(&args);
+ if (ret)
+ goto out;
+
+ dmirror_migrate_alloc_and_copy(&args, dmirror);
+ migrate_vma_pages(&args);
+ dmirror_migrate_finalize_and_map(&args, dmirror);
+ migrate_vma_finalize(&args);
+ }
+ up_read(&mm->mmap_sem);
+ mmput(mm);
+
+ /* Return the migrated data for verification. */
+ ret = dmirror_bounce_init(&bounce, start, size);
+ if (ret)
+ return ret;
+ mutex_lock(&dmirror->mutex);
+ ret = dmirror_do_read(dmirror, start, end, &bounce);
+ mutex_unlock(&dmirror->mutex);
+ if (ret == 0)
+ ret = copy_to_user(u64_to_user_ptr(cmd->ptr), bounce.ptr,
+ bounce.size);
+ cmd->cpages = bounce.cpages;
+ dmirror_bounce_fini(&bounce);
+ return ret;
+
+out:
+ up_read(&mm->mmap_sem);
+ mmput(mm);
+ return ret;
+}
+
+static void dmirror_mkentry(struct dmirror *dmirror, struct hmm_range *range,
+ unsigned char *perm, uint64_t entry)
+{
+ struct page *page;
+
+ if (entry == range->values[HMM_PFN_ERROR]) {
+ *perm = HMM_DMIRROR_PROT_ERROR;
+ return;
+ }
+ page = hmm_device_entry_to_page(range, entry);
+ if (!page) {
+ *perm = HMM_DMIRROR_PROT_NONE;
+ return;
+ }
+ if (is_device_private_page(page)) {
+ /* Is the page migrated to this device or some other? */
+ if (dmirror->mdevice == dmirror_page_to_device(page))
+ *perm = HMM_DMIRROR_PROT_DEV_PRIVATE_LOCAL;
+ else
+ *perm = HMM_DMIRROR_PROT_DEV_PRIVATE_REMOTE;
+ } else if (is_zero_pfn(page_to_pfn(page)))
+ *perm = HMM_DMIRROR_PROT_ZERO;
+ else
+ *perm = HMM_DMIRROR_PROT_NONE;
+ if (entry & range->flags[HMM_PFN_WRITE])
+ *perm |= HMM_DMIRROR_PROT_WRITE;
+ else
+ *perm |= HMM_DMIRROR_PROT_READ;
+}
+
+static bool dmirror_snapshot_invalidate(struct mmu_interval_notifier *mni,
+ const struct mmu_notifier_range *range,
+ unsigned long cur_seq)
+{
+ struct dmirror_interval *dmi =
+ container_of(mni, struct dmirror_interval, notifier);
+ struct dmirror *dmirror = dmi->dmirror;
+
+ if (mmu_notifier_range_blockable(range))
+ mutex_lock(&dmirror->mutex);
+ else if (!mutex_trylock(&dmirror->mutex))
+ return false;
+
+ /*
+ * Snapshots only need to set the sequence number since any
+ * invalidation in the interval invalidates the whole snapshot.
+ */
+ mmu_interval_set_seq(mni, cur_seq);
+
+ mutex_unlock(&dmirror->mutex);
+ return true;
+}
+
+static const struct mmu_interval_notifier_ops dmirror_mrn_ops = {
+ .invalidate = dmirror_snapshot_invalidate,
+};
+
+static int dmirror_range_snapshot(struct dmirror *dmirror,
+ struct hmm_range *range,
+ unsigned char *perm)
+{
+ struct mm_struct *mm = dmirror->notifier.mm;
+ struct dmirror_interval notifier;
+ unsigned long timeout =
+ jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
+ unsigned long i;
+ unsigned long n;
+ int ret = 0;
+
+ notifier.dmirror = dmirror;
+ range->notifier = &notifier.notifier;
+
+ ret = mmu_interval_notifier_insert(range->notifier, mm,
+ range->start, range->end - range->start,
+ &dmirror_mrn_ops);
+ if (ret)
+ return ret;
+
+ while (true) {
+ long count;
+
+ if (time_after(jiffies, timeout)) {
+ ret = -EBUSY;
+ goto out;
+ }
+
+ range->notifier_seq = mmu_interval_read_begin(range->notifier);
+
+ down_read(&mm->mmap_sem);
+ count = hmm_range_fault(range);
+ up_read(&mm->mmap_sem);
+ if (count <= 0) {
+ if (count == 0 || count == -EBUSY)
+ continue;
+ ret = count;
+ goto out;
+ }
+
+ mutex_lock(&dmirror->mutex);
+ if (mmu_interval_read_retry(range->notifier,
+ range->notifier_seq)) {
+ mutex_unlock(&dmirror->mutex);
+ continue;
+ }
+ break;
+ }
+
+ n = (range->end - range->start) >> PAGE_SHIFT;
+ for (i = 0; i < n; i++)
+ dmirror_mkentry(dmirror, range, perm + i, range->pfns[i]);
+
+ mutex_unlock(&dmirror->mutex);
+out:
+ mmu_interval_notifier_remove(range->notifier);
+ return ret;
+}
+
+static int dmirror_snapshot(struct dmirror *dmirror,
+ struct hmm_dmirror_cmd *cmd)
+{
+ struct mm_struct *mm = dmirror->notifier.mm;
+ unsigned long start, end;
+ unsigned long size = cmd->npages << PAGE_SHIFT;
+ unsigned long addr;
+ unsigned long next;
+ uint64_t pfns[64];
+ unsigned char perm[64];
+ char __user *uptr;
+ struct hmm_range range = {
+ .pfns = pfns,
+ .flags = dmirror_hmm_flags,
+ .values = dmirror_hmm_values,
+ .pfn_shift = DPT_SHIFT,
+ .pfn_flags_mask = 0,
+ .dev_private_owner = dmirror->mdevice,
+ };
+ int ret = 0;
+
+ start = cmd->addr;
+ end = start + size;
+ if (end < start)
+ return -EINVAL;
+
+ /* Since the mm is for the mirrored process, get a reference first. */
+ if (!mmget_not_zero(mm))
+ return -EINVAL;
+
+ /*
+ * Register a temporary notifier to detect invalidations even if it
+ * overlaps with other mmu_interval_notifiers.
+ */
+ uptr = u64_to_user_ptr(cmd->ptr);
+ for (addr = start; addr < end; addr = next) {
+ unsigned long n;
+
+ next = min(addr + (ARRAY_SIZE(pfns) << PAGE_SHIFT), end);
+ range.start = addr;
+ range.end = next;
+
+ ret = dmirror_range_snapshot(dmirror, &range, perm);
+ if (ret)
+ break;
+
+ n = (range.end - range.start) >> PAGE_SHIFT;
+ ret = copy_to_user(uptr, perm, n);
+ if (ret)
+ break;
+
+ cmd->cpages += n;
+ uptr += n;
+ }
+ mmput(mm);
+
+ return ret;
+}
+
+static long dmirror_fops_unlocked_ioctl(struct file *filp,
+ unsigned int command,
+ unsigned long arg)
+{
+ void __user *uarg = (void __user *)arg;
+ struct hmm_dmirror_cmd cmd;
+ struct dmirror *dmirror;
+ int ret;
+
+ dmirror = filp->private_data;
+ if (!dmirror)
+ return -EINVAL;
+
+ ret = copy_from_user(&cmd, uarg, sizeof(cmd));
+ if (ret)
+ return ret;
+
+ if (cmd.addr & ~PAGE_MASK)
+ return -EINVAL;
+ if (cmd.addr >= (cmd.addr + (cmd.npages << PAGE_SHIFT)))
+ return -EINVAL;
+
+ cmd.cpages = 0;
+ cmd.faults = 0;
+
+ switch (command) {
+ case HMM_DMIRROR_READ:
+ ret = dmirror_read(dmirror, &cmd);
+ break;
+
+ case HMM_DMIRROR_WRITE:
+ ret = dmirror_write(dmirror, &cmd);
+ break;
+
+ case HMM_DMIRROR_MIGRATE:
+ ret = dmirror_migrate(dmirror, &cmd);
+ break;
+
+ case HMM_DMIRROR_SNAPSHOT:
+ ret = dmirror_snapshot(dmirror, &cmd);
+ break;
+
+ default:
+ return -EINVAL;
+ }
+ if (ret)
+ return ret;
+
+ return copy_to_user(uarg, &cmd, sizeof(cmd));
+}
+
+static const struct file_operations dmirror_fops = {
+ .open = dmirror_fops_open,
+ .release = dmirror_fops_release,
+ .unlocked_ioctl = dmirror_fops_unlocked_ioctl,
+ .llseek = default_llseek,
+ .owner = THIS_MODULE,
+};
+
+static void dmirror_devmem_free(struct page *page)
+{
+ struct page *rpage = page->zone_device_data;
+ struct dmirror_device *mdevice;
+
+ if (rpage)
+ __free_page(rpage);
+
+ mdevice = dmirror_page_to_device(page);
+
+ spin_lock(&mdevice->lock);
+ mdevice->cfree++;
+ page->zone_device_data = mdevice->free_pages;
+ mdevice->free_pages = page;
+ spin_unlock(&mdevice->lock);
+}
+
+static vm_fault_t dmirror_devmem_fault_alloc_and_copy(struct migrate_vma *args,
+ struct dmirror_device *mdevice)
+{
+ const unsigned long *src = args->src;
+ unsigned long *dst = args->dst;
+ unsigned long start = args->start;
+ unsigned long end = args->end;
+ unsigned long addr;
+
+ for (addr = start; addr < end; addr += PAGE_SIZE,
+ src++, dst++) {
+ struct page *dpage, *spage;
+
+ spage = migrate_pfn_to_page(*src);
+ if (!spage || !(*src & MIGRATE_PFN_MIGRATE))
+ continue;
+ spage = spage->zone_device_data;
+
+ dpage = alloc_page_vma(GFP_HIGHUSER_MOVABLE, args->vma, addr);
+ if (!dpage)
+ continue;
+
+ lock_page(dpage);
+ copy_highpage(dpage, spage);
+ *dst = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_LOCKED;
+ if (*src & MIGRATE_PFN_WRITE)
+ *dst |= MIGRATE_PFN_WRITE;
+ }
+ return 0;
+}
+
+static void dmirror_devmem_fault_finalize_and_map(struct migrate_vma *args,
+ struct dmirror *dmirror)
+{
+ /* Invalidate the device's page table mapping. */
+ mutex_lock(&dmirror->mutex);
+ dmirror_do_update(dmirror, args->start, args->end);
+ mutex_unlock(&dmirror->mutex);
+}
+
+static vm_fault_t dmirror_devmem_fault(struct vm_fault *vmf)
+{
+ struct migrate_vma args;
+ unsigned long src_pfns;
+ unsigned long dst_pfns;
+ struct page *rpage;
+ struct dmirror *dmirror;
+ vm_fault_t ret;
+
+ /*
+ * Normally, a device would use the page->zone_device_data to point to
+ * the mirror but here we use it to hold the page for the simulated
+ * device memory and that page holds the pointer to the mirror.
+ */
+ rpage = vmf->page->zone_device_data;
+ dmirror = rpage->zone_device_data;
+
+ /* FIXME demonstrate how we can adjust migrate range */
+ args.vma = vmf->vma;
+ args.start = vmf->address;
+ args.end = args.start + PAGE_SIZE;
+ args.src = &src_pfns;
+ args.dst = &dst_pfns;
+ args.src_owner = dmirror->mdevice;
+
+ if (migrate_vma_setup(&args))
+ return VM_FAULT_SIGBUS;
+
+ ret = dmirror_devmem_fault_alloc_and_copy(&args, dmirror->mdevice);
+ if (ret)
+ return ret;
+ migrate_vma_pages(&args);
+ dmirror_devmem_fault_finalize_and_map(&args, dmirror);
+ migrate_vma_finalize(&args);
+ return 0;
+}
+
+static const struct dev_pagemap_ops dmirror_devmem_ops = {
+ .page_free = dmirror_devmem_free,
+ .migrate_to_ram = dmirror_devmem_fault,
+};
+
+static int dmirror_device_init(struct dmirror_device *mdevice, int id)
+{
+ dev_t dev;
+ int ret;
+
+ dev = MKDEV(MAJOR(dmirror_dev), id);
+ mutex_init(&mdevice->devmem_lock);
+ spin_lock_init(&mdevice->lock);
+
+ cdev_init(&mdevice->cdevice, &dmirror_fops);
+ ret = cdev_add(&mdevice->cdevice, dev, 1);
+ if (ret)
+ return ret;
+
+ /* Build a list of free ZONE_DEVICE private struct pages */
+ dmirror_allocate_chunk(mdevice, NULL);
+
+ return 0;
+}
+
+static void dmirror_device_remove(struct dmirror_device *mdevice)
+{
+ unsigned int i;
+
+ if (mdevice->devmem_chunks) {
+ for (i = 0; i < mdevice->devmem_count; i++) {
+ struct dmirror_chunk *devmem =
+ mdevice->devmem_chunks[i];
+
+ memunmap_pages(&devmem->pagemap);
+ kfree(devmem);
+ }
+ kfree(mdevice->devmem_chunks);
+ }
+
+ cdev_del(&mdevice->cdevice);
+}
+
+static int __init hmm_dmirror_init(void)
+{
+ int ret;
+ int id;
+
+ ret = alloc_chrdev_region(&dmirror_dev, 0, DMIRROR_NDEVICES,
+ "HMM_DMIRROR");
+ if (ret)
+ goto err_unreg;
+
+ for (id = 0; id < DMIRROR_NDEVICES; id++) {
+ ret = dmirror_device_init(dmirror_devices + id, id);
+ if (ret)
+ goto err_chrdev;
+ }
+
+ /*
+ * Allocate a zero page to simulate a reserved page of device private
+ * memory which is always zero. The zero_pfn page isn't used just to
+ * make the code here simpler (i.e., we need a struct page for it).
+ */
+ dmirror_zero_page = alloc_page(GFP_HIGHUSER | __GFP_ZERO);
+ if (!dmirror_zero_page)
+ goto err_chrdev;
+
+ pr_info("HMM test module loaded. This is only for testing HMM.\n");
+ return 0;
+
+err_chrdev:
+ while (--id >= 0)
+ dmirror_device_remove(dmirror_devices + id);
+ unregister_chrdev_region(dmirror_dev, DMIRROR_NDEVICES);
+err_unreg:
+ return ret;
+}
+
+static void __exit hmm_dmirror_exit(void)
+{
+ int id;
+
+ if (dmirror_zero_page)
+ __free_page(dmirror_zero_page);
+ for (id = 0; id < DMIRROR_NDEVICES; id++)
+ dmirror_device_remove(dmirror_devices + id);
+ unregister_chrdev_region(dmirror_dev, DMIRROR_NDEVICES);
+}
+
+module_init(hmm_dmirror_init);
+module_exit(hmm_dmirror_exit);
+MODULE_LICENSE("GPL");
--
2.20.1