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KVM: selftests: Add basic selftest for guest_memfd()
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Add a selftest to verify the basic functionality of guest_memfd():

+ file descriptor created with the guest_memfd() ioctl does not allow
  read/write/mmap operations
+ file size and block size as returned from fstat are as expected
+ fallocate on the fd checks that offset/length on
  fallocate(FALLOC_FL_PUNCH_HOLE) should be page aligned
+ invalid inputs (misaligned size, invalid flags) are rejected
+ file size and inode are unique (the innocuous-sounding
  anon_inode_getfile() backs all files with a single inode...)

Signed-off-by: Chao Peng <[email protected]>
Co-developed-by: Ackerley Tng <[email protected]>
Signed-off-by: Ackerley Tng <[email protected]>
Co-developed-by: Paolo Bonzini <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
Co-developed-by: Sean Christopherson <[email protected]>
Signed-off-by: Sean Christopherson <[email protected]>
Message-Id: <[email protected]>
Reviewed-by: Fuad Tabba <[email protected]>
Tested-by: Fuad Tabba <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
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@chao-p @bonzini
chao-p authored and bonzini committed Nov 14, 2023
1 parent 2feabb8 commit 8a89efd
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1 change: 1 addition & 0 deletions tools/testing/selftests/kvm/Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -134,6 +134,7 @@ TEST_GEN_PROGS_x86_64 += access_tracking_perf_test
TEST_GEN_PROGS_x86_64 += demand_paging_test
TEST_GEN_PROGS_x86_64 += dirty_log_test
TEST_GEN_PROGS_x86_64 += dirty_log_perf_test
TEST_GEN_PROGS_x86_64 += guest_memfd_test
TEST_GEN_PROGS_x86_64 += guest_print_test
TEST_GEN_PROGS_x86_64 += hardware_disable_test
TEST_GEN_PROGS_x86_64 += kvm_create_max_vcpus
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207 changes: 207 additions & 0 deletions tools/testing/selftests/kvm/guest_memfd_test.c
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@@ -0,0 +1,207 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright Intel Corporation, 2023
*
* Author: Chao Peng <[email protected]>
*/

#define _GNU_SOURCE
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#include <fcntl.h>

#include <linux/bitmap.h>
#include <linux/falloc.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>

#include "test_util.h"
#include "kvm_util_base.h"

static void test_file_read_write(int fd)
{
char buf[64];

TEST_ASSERT(read(fd, buf, sizeof(buf)) < 0,
"read on a guest_mem fd should fail");
TEST_ASSERT(write(fd, buf, sizeof(buf)) < 0,
"write on a guest_mem fd should fail");
TEST_ASSERT(pread(fd, buf, sizeof(buf), 0) < 0,
"pread on a guest_mem fd should fail");
TEST_ASSERT(pwrite(fd, buf, sizeof(buf), 0) < 0,
"pwrite on a guest_mem fd should fail");
}

static void test_mmap(int fd, size_t page_size)
{
char *mem;

mem = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
TEST_ASSERT_EQ(mem, MAP_FAILED);
}

static void test_file_size(int fd, size_t page_size, size_t total_size)
{
struct stat sb;
int ret;

ret = fstat(fd, &sb);
TEST_ASSERT(!ret, "fstat should succeed");
TEST_ASSERT_EQ(sb.st_size, total_size);
TEST_ASSERT_EQ(sb.st_blksize, page_size);
}

static void test_fallocate(int fd, size_t page_size, size_t total_size)
{
int ret;

ret = fallocate(fd, FALLOC_FL_KEEP_SIZE, 0, total_size);
TEST_ASSERT(!ret, "fallocate with aligned offset and size should succeed");

ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
page_size - 1, page_size);
TEST_ASSERT(ret, "fallocate with unaligned offset should fail");

ret = fallocate(fd, FALLOC_FL_KEEP_SIZE, total_size, page_size);
TEST_ASSERT(ret, "fallocate beginning at total_size should fail");

ret = fallocate(fd, FALLOC_FL_KEEP_SIZE, total_size + page_size, page_size);
TEST_ASSERT(ret, "fallocate beginning after total_size should fail");

ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
total_size, page_size);
TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) at total_size should succeed");

ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
total_size + page_size, page_size);
TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) after total_size should succeed");

ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
page_size, page_size - 1);
TEST_ASSERT(ret, "fallocate with unaligned size should fail");

ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
page_size, page_size);
TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) with aligned offset and size should succeed");

ret = fallocate(fd, FALLOC_FL_KEEP_SIZE, page_size, page_size);
TEST_ASSERT(!ret, "fallocate to restore punched hole should succeed");
}

static void test_invalid_punch_hole(int fd, size_t page_size, size_t total_size)
{
struct {
off_t offset;
off_t len;
} testcases[] = {
{0, 1},
{0, page_size - 1},
{0, page_size + 1},

{1, 1},
{1, page_size - 1},
{1, page_size},
{1, page_size + 1},

{page_size, 1},
{page_size, page_size - 1},
{page_size, page_size + 1},
};
int ret, i;

for (i = 0; i < ARRAY_SIZE(testcases); i++) {
ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
testcases[i].offset, testcases[i].len);
TEST_ASSERT(ret == -1 && errno == EINVAL,
"PUNCH_HOLE with !PAGE_SIZE offset (%lx) and/or length (%lx) should fail",
testcases[i].offset, testcases[i].len);
}
}

static void test_create_guest_memfd_invalid(struct kvm_vm *vm)
{
size_t page_size = getpagesize();
uint64_t flag;
size_t size;
int fd;

for (size = 1; size < page_size; size++) {
fd = __vm_create_guest_memfd(vm, size, 0);
TEST_ASSERT(fd == -1 && errno == EINVAL,
"guest_memfd() with non-page-aligned page size '0x%lx' should fail with EINVAL",
size);
}

for (flag = 1; flag; flag <<= 1) {
uint64_t bit;

fd = __vm_create_guest_memfd(vm, page_size, flag);
TEST_ASSERT(fd == -1 && errno == EINVAL,
"guest_memfd() with flag '0x%lx' should fail with EINVAL",
flag);

for_each_set_bit(bit, &valid_flags, 64) {
fd = __vm_create_guest_memfd(vm, page_size, flag | BIT_ULL(bit));
TEST_ASSERT(fd == -1 && errno == EINVAL,
"guest_memfd() with flags '0x%llx' should fail with EINVAL",
flag | BIT_ULL(bit));
}
}
}

static void test_create_guest_memfd_multiple(struct kvm_vm *vm)
{
int fd1, fd2, ret;
struct stat st1, st2;

fd1 = __vm_create_guest_memfd(vm, 4096, 0);
TEST_ASSERT(fd1 != -1, "memfd creation should succeed");

ret = fstat(fd1, &st1);
TEST_ASSERT(ret != -1, "memfd fstat should succeed");
TEST_ASSERT(st1.st_size == 4096, "memfd st_size should match requested size");

fd2 = __vm_create_guest_memfd(vm, 8192, 0);
TEST_ASSERT(fd2 != -1, "memfd creation should succeed");

ret = fstat(fd2, &st2);
TEST_ASSERT(ret != -1, "memfd fstat should succeed");
TEST_ASSERT(st2.st_size == 8192, "second memfd st_size should match requested size");

ret = fstat(fd1, &st1);
TEST_ASSERT(ret != -1, "memfd fstat should succeed");
TEST_ASSERT(st1.st_size == 4096, "first memfd st_size should still match requested size");
TEST_ASSERT(st1.st_ino != st2.st_ino, "different memfd should have different inode numbers");
}

int main(int argc, char *argv[])
{
size_t page_size;
size_t total_size;
int fd;
struct kvm_vm *vm;

TEST_REQUIRE(kvm_has_cap(KVM_CAP_GUEST_MEMFD));

page_size = getpagesize();
total_size = page_size * 4;

vm = vm_create_barebones();

test_create_guest_memfd_invalid(vm);
test_create_guest_memfd_multiple(vm);

fd = vm_create_guest_memfd(vm, total_size, 0);

test_file_read_write(fd);
test_mmap(fd, page_size);
test_file_size(fd, page_size, total_size);
test_fallocate(fd, page_size, total_size);
test_invalid_punch_hole(fd, page_size, total_size);

close(fd);
}

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