// SPDX-License-Identifier: GPL-2.0-only
/*
* Usage: to be run via nx_huge_page_test.sh, which does the necessary
* environment setup and teardown
*
* Copyright (C) 2022, Google LLC.
*/
#include <fcntl.h>
#include <stdint.h>
#include <time.h>
#include <test_util.h>
#include "kvm_util.h"
#include "processor.h"
#define HPAGE_SLOT 10
#define HPAGE_GPA (4UL << 30) /* 4G prevents collision w/ slot 0 */
#define HPAGE_GVA HPAGE_GPA /* GVA is arbitrary, so use GPA. */
#define PAGES_PER_2MB_HUGE_PAGE 512
#define HPAGE_SLOT_NPAGES (3 * PAGES_PER_2MB_HUGE_PAGE)
/*
* Passed by nx_huge_pages_test.sh to provide an easy warning if this test is
* being run without it.
*/
#define MAGIC_TOKEN 887563923
/*
* x86 opcode for the return instruction. Used to call into, and then
* immediately return from, memory backed with hugepages.
*/
#define RETURN_OPCODE 0xC3
/* Call the specified memory address. */
static void guest_do_CALL(uint64_t target)
{
((void (*)(void)) target)();
}
/*
* Exit the VM after each memory access so that the userspace component of the
* test can make assertions about the pages backing the VM.
*
* See the below for an explanation of how each access should affect the
* backing mappings.
*/
void guest_code(void)
{
uint64_t hpage_1 = HPAGE_GVA;
uint64_t hpage_2 = hpage_1 + (PAGE_SIZE * 512);
uint64_t hpage_3 = hpage_2 + (PAGE_SIZE * 512);
READ_ONCE(*(uint64_t *)hpage_1);
GUEST_SYNC(1);
READ_ONCE(*(uint64_t *)hpage_2);
GUEST_SYNC(2);
guest_do_CALL(hpage_1);
GUEST_SYNC(3);
guest_do_CALL(hpage_3);
GUEST_SYNC(4);
READ_ONCE(*(uint64_t *)hpage_1);
GUEST_SYNC(5);
READ_ONCE(*(uint64_t *)hpage_3);
GUEST_SYNC(6);
}
static void check_2m_page_count(struct kvm_vm *vm, int expected_pages_2m)
{
int actual_pages_2m;
actual_pages_2m = vm_get_stat(vm, "pages_2m");
TEST_ASSERT(actual_pages_2m == expected_pages_2m,
"Unexpected 2m page count. Expected %d, got %d",
expected_pages_2m, actual_pages_2m);
}
static void check_split_count(struct kvm_vm *vm, int expected_splits)
{
int actual_splits;
actual_splits = vm_get_stat(vm, "nx_lpage_splits");
TEST_ASSERT(actual_splits == expected_splits,
"Unexpected NX huge page split count. Expected %d, got %d",
expected_splits, actual_splits);
}
static void wait_for_reclaim(int reclaim_period_ms)
{
long reclaim_wait_ms;
struct timespec ts;
reclaim_wait_ms = reclaim_period_ms * 5;
ts.tv_sec = reclaim_wait_ms / 1000;
ts.tv_nsec = (reclaim_wait_ms - (ts.tv_sec * 1000)) * 1000000;
nanosleep(&ts, NULL);
}
void run_test(int reclaim_period_ms, bool disable_nx_huge_pages,
bool reboot_permissions)
{
struct kvm_vcpu *vcpu;
struct kvm_vm *vm;
uint64_t nr_bytes;
void *hva;
int r;
vm = vm_create(1);
if (disable_nx_huge_pages) {
r = __vm_disable_nx_huge_pages(vm);
if (reboot_permissions) {
TEST_ASSERT(!r, "Disabling NX huge pages should succeed if process has reboot permissions");
} else {
TEST_ASSERT(r == -1 && errno == EPERM,
"This process should not have permission to disable NX huge pages");
return;
}
}
vcpu = vm_vcpu_add(vm, 0, guest_code);
vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS_HUGETLB,
HPAGE_GPA, HPAGE_SLOT,
HPAGE_SLOT_NPAGES, 0);
nr_bytes = HPAGE_SLOT_NPAGES * vm->page_size;
/*
* Ensure that KVM can map HPAGE_SLOT with huge pages by mapping the
* region into the guest with 2MiB pages whenever TDP is disabled (i.e.
* whenever KVM is shadowing the guest page tables).
*
* When TDP is enabled, KVM should be able to map HPAGE_SLOT with huge
* pages irrespective of the guest page size, so map with 4KiB pages
* to test that that is the case.
*/
if (kvm_is_tdp_enabled())
virt_map_level(vm, HPAGE_GVA, HPAGE_GPA, nr_bytes, PG_LEVEL_4K);
else
virt_map_level(vm, HPAGE_GVA, HPAGE_GPA, nr_bytes, PG_LEVEL_2M);
hva = addr_gpa2hva(vm, HPAGE_GPA);
memset(hva, RETURN_OPCODE, nr_bytes);
check_2m_page_count(vm, 0);
check_split_count(vm, 0);
/*
* The guest code will first read from the first hugepage, resulting
* in a huge page mapping being created.
*/
vcpu_run(vcpu);
check_2m_page_count(vm, 1);
check_split_count(vm, 0);
/*
* Then the guest code will read from the second hugepage, resulting
* in another huge page mapping being created.
*/
vcpu_run(vcpu);
check_2m_page_count(vm, 2);
check_split_count(vm, 0);
/*
* Next, the guest will execute from the first huge page, causing it
* to be remapped at 4k.
*
* If NX huge pages are disabled, this should have no effect.
*/
vcpu_run(vcpu);
check_2m_page_count(vm, disable_nx_huge_pages ? 2 : 1);
check_split_count(vm, disable_nx_huge_pages ? 0 : 1);
/*
* Executing from the third huge page (previously unaccessed) will
* cause part to be mapped at 4k.
*
* If NX huge pages are disabled, it should be mapped at 2M.
*/
vcpu_run(vcpu);
check_2m_page_count(vm, disable_nx_huge_pages ? 3 : 1);
check_split_count(vm, disable_nx_huge_pages ? 0 : 2);
/* Reading from the first huge page again should have no effect. */
vcpu_run(vcpu);
check_2m_page_count(vm, disable_nx_huge_pages ? 3 : 1);
check_split_count(vm, disable_nx_huge_pages ? 0 : 2);
/* Give recovery thread time to run. */
wait_for_reclaim(reclaim_period_ms);
/*
* Now that the reclaimer has run, all the split pages should be gone.
*
* If NX huge pages are disabled, the relaimer will not run, so
* nothing should change from here on.
*/
check_2m_page_count(vm, disable_nx_huge_pages ? 3 : 1);
check_split_count(vm, 0);
/*
* The 4k mapping on hpage 3 should have been removed, so check that
* reading from it causes a huge page mapping to be installed.
*/
vcpu_run(vcpu);
check_2m_page_count(vm, disable_nx_huge_pages ? 3 : 2);
check_split_count(vm, 0);
kvm_vm_free(vm);
}
static void help(char *name)
{
puts("");
printf("usage: %s [-h] [-p period_ms] [-t token]\n", name);
puts("");
printf(" -p: The NX reclaim period in milliseconds.\n");
printf(" -t: The magic token to indicate environment setup is done.\n");
printf(" -r: The test has reboot permissions and can disable NX huge pages.\n");
puts("");
exit(0);
}
int main(int argc, char **argv)
{
int reclaim_period_ms = 0, token = 0, opt;
bool reboot_permissions = false;
while ((opt = getopt(argc, argv, "hp:t:r")) != -1) {
switch (opt) {
case 'p':
reclaim_period_ms = atoi_positive("Reclaim period", optarg);
break;
case 't':
token = atoi_paranoid(optarg);
break;
case 'r':
reboot_permissions = true;
break;
case 'h':
default:
help(argv[0]);
break;
}
}
TEST_REQUIRE(kvm_has_cap(KVM_CAP_VM_DISABLE_NX_HUGE_PAGES));
__TEST_REQUIRE(token == MAGIC_TOKEN,
"This test must be run with the magic token via '-t %d'.\n"
"Running via nx_huge_pages_test.sh, which also handles "
"environment setup, is strongly recommended.", MAGIC_TOKEN);
run_test(reclaim_period_ms, false, reboot_permissions);
run_test(reclaim_period_ms, true, reboot_permissions);
return 0;
}
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