Quelle  userfaultfd_util.c   Sprache: C

// SPDX-License-Identifier: GPL-2.0
/*
 * KVM userfaultfd util
 * Adapted from demand_paging_test.c
 *
 * Copyright (C) 2018, Red Hat, Inc.
 * Copyright (C) 2019-2022 Google LLC
 */
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <poll.h>
#include <pthread.h>
#include <linux/userfaultfd.h>
#include <sys/epoll.h>
#include <sys/syscall.h>

#include "kvm_util.h"
#include "test_util.h"
#include "memstress.h"
#include "userfaultfd_util.h"

#ifdef __NR_userfaultfd

static void *uffd_handler_thread_fn(void *arg)
{
 struct uffd_reader_args *reader_args = (struct uffd_reader_args *)arg;
 int uffd = reader_args->uffd;
 int64_t pages = 0;
 struct timespec start;
 struct timespec ts_diff;
 struct epoll_event evt;
 int epollfd;

 epollfd = epoll_create(1);
 TEST_ASSERT(epollfd >= 0, "Failed to create epollfd.");

 evt.events = EPOLLIN | EPOLLEXCLUSIVE;
 evt.data.u32 = 0;
 TEST_ASSERT(!epoll_ctl(epollfd, EPOLL_CTL_ADD, uffd, &evt),
      "Failed to add uffd to epollfd");

 evt.events = EPOLLIN;
 evt.data.u32 = 1;
 TEST_ASSERT(!epoll_ctl(epollfd, EPOLL_CTL_ADD, reader_args->pipe, &evt),
      "Failed to add pipe to epollfd");

 clock_gettime(CLOCK_MONOTONIC, &start);
 while (1) {
  struct uffd_msg msg;
  int r;

  r = epoll_wait(epollfd, &evt, 1, -1);
  TEST_ASSERT(r == 1,
       "Unexpected number of events (%d) from epoll, errno = %d",
       r, errno);

  if (evt.data.u32 == 1) {
   char tmp_chr;

   TEST_ASSERT(!(evt.events & (EPOLLERR | EPOLLHUP)),
        "Reader thread received EPOLLERR or EPOLLHUP on pipe.");
   r = read(reader_args->pipe, &tmp_chr, 1);
   TEST_ASSERT(r == 1,
        "Error reading pipefd in uffd reader thread");
   break;
  }

  TEST_ASSERT(!(evt.events & (EPOLLERR | EPOLLHUP)),
       "Reader thread received EPOLLERR or EPOLLHUP on uffd.");

  r = read(uffd, &msg, sizeof(msg));
  if (r == -1) {
   TEST_ASSERT(errno == EAGAIN,
        "Error reading from UFFD: errno = %d", errno);
   continue;
  }

  TEST_ASSERT(r == sizeof(msg),
       "Read on uffd returned unexpected number of bytes (%d)", r);

  if (!(msg.event & UFFD_EVENT_PAGEFAULT))
   continue;

  if (reader_args->delay)
   usleep(reader_args->delay);
  r = reader_args->handler(reader_args->uffd_mode, uffd, &msg);
  TEST_ASSERT(r >= 0,
       "Reader thread handler fn returned negative value %d", r);
  pages++;
 }

 ts_diff = timespec_elapsed(start);
 PER_VCPU_DEBUG("userfaulted %ld pages over %ld.%.9lds. (%f/sec)\n",
         pages, ts_diff.tv_sec, ts_diff.tv_nsec,
         pages / ((double)ts_diff.tv_sec + (double)ts_diff.tv_nsec / NSEC_PER_SEC));

 return NULL;
}

struct uffd_desc *uffd_setup_demand_paging(int uffd_mode, useconds_t delay,
        void *hva, uint64_t len,
        uint64_t num_readers,
        uffd_handler_t handler)
{
 struct uffd_desc *uffd_desc;
 bool is_minor = (uffd_mode == UFFDIO_REGISTER_MODE_MINOR);
 int uffd;
 struct uffdio_api uffdio_api;
 struct uffdio_register uffdio_register;
 uint64_t expected_ioctls = ((uint64_t) 1) << _UFFDIO_COPY;
 int ret, i;

 PER_PAGE_DEBUG("Userfaultfd %s mode, faults resolved with %s\n",
         is_minor ? "MINOR" : "MISSING",
         is_minor ? "UFFDIO_CONTINUE" : "UFFDIO_COPY");

 uffd_desc = malloc(sizeof(struct uffd_desc));
 TEST_ASSERT(uffd_desc, "Failed to malloc uffd descriptor");

 uffd_desc->pipefds = calloc(sizeof(int), num_readers);
 TEST_ASSERT(uffd_desc->pipefds, "Failed to alloc pipes");

 uffd_desc->readers = calloc(sizeof(pthread_t), num_readers);
 TEST_ASSERT(uffd_desc->readers, "Failed to alloc reader threads");

 uffd_desc->reader_args = calloc(sizeof(struct uffd_reader_args), num_readers);
 TEST_ASSERT(uffd_desc->reader_args, "Failed to alloc reader_args");

 uffd_desc->num_readers = num_readers;

 /* In order to get minor faults, prefault via the alias. */
 if (is_minor)
  expected_ioctls = ((uint64_t) 1) << _UFFDIO_CONTINUE;

 uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
 TEST_ASSERT(uffd >= 0, "uffd creation failed, errno: %d", errno);

 uffdio_api.api = UFFD_API;
 uffdio_api.features = 0;
 TEST_ASSERT(ioctl(uffd, UFFDIO_API, &uffdio_api) != -1,
      "ioctl UFFDIO_API failed: %" PRIu64,
      (uint64_t)uffdio_api.api);

 uffdio_register.range.start = (uint64_t)hva;
 uffdio_register.range.len = len;
 uffdio_register.mode = uffd_mode;
 TEST_ASSERT(ioctl(uffd, UFFDIO_REGISTER, &uffdio_register) != -1,
      "ioctl UFFDIO_REGISTER failed");
 TEST_ASSERT((uffdio_register.ioctls & expected_ioctls) ==
      expected_ioctls, "missing userfaultfd ioctls");

 uffd_desc->uffd = uffd;
 for (i = 0; i < uffd_desc->num_readers; ++i) {
  int pipes[2];

  ret = pipe2((int *) &pipes, O_CLOEXEC | O_NONBLOCK);
  TEST_ASSERT(!ret, "Failed to set up pipefd %i for uffd_desc %p",
       i, uffd_desc);

  uffd_desc->pipefds[i] = pipes[1];

  uffd_desc->reader_args[i].uffd_mode = uffd_mode;
  uffd_desc->reader_args[i].uffd = uffd;
  uffd_desc->reader_args[i].delay = delay;
  uffd_desc->reader_args[i].handler = handler;
  uffd_desc->reader_args[i].pipe = pipes[0];

  pthread_create(&uffd_desc->readers[i], NULL, uffd_handler_thread_fn,
          &uffd_desc->reader_args[i]);

  PER_VCPU_DEBUG("Created uffd thread %i for HVA range [%p, %p)\n",
          i, hva, hva + len);
 }

 return uffd_desc;
}

void uffd_stop_demand_paging(struct uffd_desc *uffd)
{
 char c = 0;
 int i;

 for (i = 0; i < uffd->num_readers; ++i)
  TEST_ASSERT(write(uffd->pipefds[i], &c, 1) == 1,
       "Unable to write to pipefd %i for uffd_desc %p", i, uffd);

 for (i = 0; i < uffd->num_readers; ++i)
  TEST_ASSERT(!pthread_join(uffd->readers[i], NULL),
       "Pthread_join failed on reader %i for uffd_desc %p", i, uffd);

 close(uffd->uffd);

 for (i = 0; i < uffd->num_readers; ++i) {
  close(uffd->pipefds[i]);
  close(uffd->reader_args[i].pipe);
 }

 free(uffd->pipefds);
 free(uffd->readers);
 free(uffd->reader_args);
 free(uffd);
}

#endif /* __NR_userfaultfd */