shared_zeropage_test.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * Test shared zeropage handling (with/without storage keys)
  4 *
  5 * Copyright (C) 2024, Red Hat, Inc.
  6 */
  7#include <sys/mman.h>
  8
  9#include <linux/fs.h>
 10
 11#include "test_util.h"
 12#include "kvm_util.h"
 13#include "kselftest.h"
 14#include "ucall_common.h"
 15
 16static void set_storage_key(void *addr, uint8_t skey)
 17{
 18	asm volatile("sske %0,%1" : : "d" (skey), "a" (addr));
 19}
 20
 21static void guest_code(void)
 22{
 23	/* Issue some storage key instruction. */
 24	set_storage_key((void *)0, 0x98);
 25	GUEST_DONE();
 26}
 27
 28/*
 29 * Returns 1 if the shared zeropage is mapped, 0 if something else is mapped.
 30 * Returns < 0 on error or if nothing is mapped.
 31 */
 32static int maps_shared_zeropage(int pagemap_fd, void *addr)
 33{
 34	struct page_region region;
 35	struct pm_scan_arg arg = {
 36		.start = (uintptr_t)addr,
 37		.end = (uintptr_t)addr + 4096,
 38		.vec = (uintptr_t)&region,
 39		.vec_len = 1,
 40		.size = sizeof(struct pm_scan_arg),
 41		.category_mask = PAGE_IS_PFNZERO,
 42		.category_anyof_mask = PAGE_IS_PRESENT,
 43		.return_mask = PAGE_IS_PFNZERO,
 44	};
 45	return ioctl(pagemap_fd, PAGEMAP_SCAN, &arg);
 46}
 47
 48int main(int argc, char *argv[])
 49{
 50	char *mem, *page0, *page1, *page2, tmp;
 51	const size_t pagesize = getpagesize();
 52	struct kvm_vcpu *vcpu;
 53	struct kvm_vm *vm;
 54	struct ucall uc;
 55	int pagemap_fd;
 56
 57	ksft_print_header();
 58	ksft_set_plan(3);
 59
 60	/*
 61	 * We'll use memory that is not mapped into the VM for simplicity.
 62	 * Shared zeropages are enabled/disabled per-process.
 63	 */
 64	mem = mmap(0, 3 * pagesize, PROT_READ, MAP_PRIVATE | MAP_ANON, -1, 0);
 65	TEST_ASSERT(mem != MAP_FAILED, "mmap() failed");
 66
 67	/* Disable THP. Ignore errors on older kernels. */
 68	madvise(mem, 3 * pagesize, MADV_NOHUGEPAGE);
 69
 70	page0 = mem;
 71	page1 = page0 + pagesize;
 72	page2 = page1 + pagesize;
 73
 74	/* Can we even detect shared zeropages? */
 75	pagemap_fd = open("/proc/self/pagemap", O_RDONLY);
 76	TEST_REQUIRE(pagemap_fd >= 0);
 77
 78	tmp = *page0;
 79	asm volatile("" : "+r" (tmp));
 80	TEST_REQUIRE(maps_shared_zeropage(pagemap_fd, page0) == 1);
 81
 82	vm = vm_create_with_one_vcpu(&vcpu, guest_code);
 83
 84	/* Verify that we get the shared zeropage after VM creation. */
 85	tmp = *page1;
 86	asm volatile("" : "+r" (tmp));
 87	ksft_test_result(maps_shared_zeropage(pagemap_fd, page1) == 1,
 88			 "Shared zeropages should be enabled\n");
 89
 90	/*
 91	 * Let our VM execute a storage key instruction that should
 92	 * unshare all shared zeropages.
 93	 */
 94	vcpu_run(vcpu);
 95	get_ucall(vcpu, &uc);
 96	TEST_ASSERT_EQ(uc.cmd, UCALL_DONE);
 97
 98	/* Verify that we don't have a shared zeropage anymore. */
 99	ksft_test_result(!maps_shared_zeropage(pagemap_fd, page1),
100			 "Shared zeropage should be gone\n");
101
102	/* Verify that we don't get any new shared zeropages. */
103	tmp = *page2;
104	asm volatile("" : "+r" (tmp));
105	ksft_test_result(!maps_shared_zeropage(pagemap_fd, page2),
106			 "Shared zeropages should be disabled\n");
107
108	kvm_vm_free(vm);
109
110	ksft_finished();
111}