[PATCH v10 10/10] kvm: selftests: selftest for Sub-Page protection

Yang Weijiang
2019-12-31T06:47:08Z

Sub-Page Permission(SPP) is to protect finer granularity subpages
(128Byte each) within a 4KB page. It's not enabled in KVM by default,
the test first initializes the SPP runtime environment with
KVM_ENABLE_CAP ioctl, then sets protection with KVM_SUBPAGES_SET_ACCESS
for the target guest page, check permissions with KVM_SUBPAGES_GET_ACCESS
to make sure they are set as expected.

Two steps in guest code to very whether SPP is working:
1) protect all 128byte subpages, write data to each subpage
to see if SPP induced EPT violation happening. 2)unprotect all
subpages, again write data to each subpage to see if SPP still
works or not.

Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
---
tools/testing/selftests/kvm/Makefile | 2 +-
tools/testing/selftests/kvm/lib/kvm_util.c | 1 +
tools/testing/selftests/kvm/x86_64/spp_test.c | 234 ++++++++++++++++++
3 files changed, 236 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/kvm/x86_64/spp_test.c

diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index 3138a916574a..48582b7d1963 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -29,7 +29,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/xss_msr_test
TEST_GEN_PROGS_x86_64 += clear_dirty_log_test
TEST_GEN_PROGS_x86_64 += dirty_log_test
TEST_GEN_PROGS_x86_64 += kvm_create_max_vcpus
-
+TEST_GEN_PROGS_x86_64 += x86_64/spp_test
TEST_GEN_PROGS_aarch64 += clear_dirty_log_test
TEST_GEN_PROGS_aarch64 += dirty_log_test
TEST_GEN_PROGS_aarch64 += kvm_create_max_vcpus
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 41cf45416060..bc0a25f4276b 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -1486,6 +1486,7 @@ static struct exit_reason {
{KVM_EXIT_UNKNOWN, "UNKNOWN"},
{KVM_EXIT_EXCEPTION, "EXCEPTION"},
{KVM_EXIT_IO, "IO"},
+ {KVM_EXIT_SPP, "SPP"},
{KVM_EXIT_HYPERCALL, "HYPERCALL"},
{KVM_EXIT_DEBUG, "DEBUG"},
{KVM_EXIT_HLT, "HLT"},
diff --git a/tools/testing/selftests/kvm/x86_64/spp_test.c b/tools/testing/selftests/kvm/x86_64/spp_test.c
new file mode 100644
index 000000000000..2e83ff60768b
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86_64/spp_test.c
@@ -0,0 +1,234 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Sub-Page Permission test
+ *
+ * Copyright (C) 2019, Intel Corp.
+ *
+ */
+
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+
+#include "test_util.h"
+#include "kvm_util.h"
+#include "processor.h"
+#include "../../lib/kvm_util_internal.h"
+#include "linux/kvm.h"
+
+#define VCPU_ID 1
+#define PAGE_SIZE (4096)
+#define SPP_GUARD_SIZE (16 * PAGE_SIZE)
+#define SPP_GUARD_MEMSLOT (1)
+#define SPP_GUARD_PAGES (SPP_GUARD_SIZE / PAGE_SIZE)
+#define SPP_GUARD_GPA 0x10000000
+
+#define SUBPAGE_ACCESS_DEFAULT (0x0)
+#define SUBPAGE_ACCESS_FULL (0xFFFFFFFF)
+#define START_SPP_VM_ADDR (0x700000)
+#define SUBPAGE_SIZE (128)
+
+vm_vaddr_t vspp_start;
+vm_paddr_t pspp_start;
+
+void guest_code(void)
+{
+ uint8_t *iterator = (uint8_t *)vspp_start;
+ int count;
+
+ GUEST_SYNC(1);
+ /*
+ * expect EPT violation induced by SPP in each interation since
+ * the full page is protected by SPP.
+ */
+ for (count = 0; count < PAGE_SIZE / SUBPAGE_SIZE; count++) {
+ *(uint32_t *)(iterator) = 0x99;
+ iterator += SUBPAGE_SIZE;
+ }
+ GUEST_SYNC(2);
+ iterator = (uint8_t *)vspp_start;
+
+ /*
+ * don't expect EPT violation happen since SPP is disabled
+ * for the page
+ */
+ for (count = 0; count < PAGE_SIZE / SUBPAGE_SIZE; count++) {
+ *(uint32_t *)(iterator) = 0x99;
+ iterator += SUBPAGE_SIZE;
+ }
+}
+
+void prepare_test(struct kvm_vm **g_vm, struct kvm_run **g_run)
+{
+ void *spp_hva;
+ struct kvm_vm *vm;
+ struct kvm_run *run;
+ /* Create VM, SPP is only valid for 4KB page mode */
+ *g_vm = vm_create_default(VCPU_ID, 0, guest_code);
+ vm = *g_vm;
+
+ *g_run = vcpu_state(vm, VCPU_ID);
+ run = *g_run;
+
+ vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, SPP_GUARD_GPA,
+ SPP_GUARD_MEMSLOT, SPP_GUARD_PAGES, 0);
+
+ pspp_start = vm_phy_pages_alloc(vm, 1, SPP_GUARD_GPA,
+ SPP_GUARD_MEMSLOT);
+
+ memset(addr_gpa2hva(vm, SPP_GUARD_GPA), 0x0, PAGE_SIZE);
+
+ virt_map(vm, START_SPP_VM_ADDR, SPP_GUARD_GPA, PAGE_SIZE, 0);
+
+ vspp_start = vm_vaddr_alloc(vm, PAGE_SIZE, START_SPP_VM_ADDR,
+ SPP_GUARD_MEMSLOT, 0);
+
+ spp_hva = addr_gva2hva(vm, vspp_start);
+
+ pspp_start = addr_hva2gpa(vm, spp_hva);
+
+ printf("SPP protected zone: size = %d, gva = 0x%lx, gpa = 0x%lx, "
+ "hva = 0x%p\n", PAGE_SIZE, vspp_start, pspp_start, spp_hva);
+
+ /* make sure the virtual address is visible to VM. */
+ sync_global_to_guest(vm, vspp_start);
+
+ vcpu_run(vm, VCPU_ID);
+
+ TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
+ "exit reason: %u (%s),\n", run->exit_reason,
+ exit_reason_str(run->exit_reason));
+}
+
+void setup_spp(struct kvm_vm *vm)
+{
+ struct kvm_enable_cap cap;
+ int ret = 0;
+ struct kvm_subpage *sp;
+ int len;
+ memset(&cap, 0, sizeof(cap));
+ cap.cap = KVM_CAP_X86_SPP;
+ cap.flags = 0;
+
+ /* initialize the SPP runtime environment.*/
+ ret = ioctl(vm->fd, KVM_ENABLE_CAP, &cap);
+ TEST_ASSERT(ret == 0, "KVM_CAP_X86_SPP failed.");
+ len = sizeof(*sp) + sizeof(__u32);
+ printf("SPP initialized successfully.\n");
+
+ sp = malloc(len);
+ TEST_ASSERT(sp > 0, "Low memory 1!");
+ memset(sp, 0, len);
+ /* set up SPP protection for the page. */
+ sp->npages = 1;
+ sp->gfn_base = pspp_start >> 12;
+ sp->access_map[0] = SUBPAGE_ACCESS_DEFAULT;
+ ret = ioctl(vm->fd, KVM_SUBPAGES_SET_ACCESS, sp);
+
+ TEST_ASSERT(ret == 1, "KVM_SUBPAGES_SET_ACCESS failed. ret = 0x%x, "
+ "gfn_base = 0x%llx\n", ret, sp->gfn_base);
+ printf("set spp protection info: gfn = 0x%llx, access = 0x%x, "
+ "npages = %d\n", sp->gfn_base, sp->access_map[0],
+ sp->npages);
+
+ memset(sp, 0, len);
+ /* make sure the SPP permission bits are actully set as expected. */
+ sp->npages = 1;
+ sp->gfn_base = pspp_start >> 12;
+
+ ret = ioctl(vm->fd, KVM_SUBPAGES_GET_ACCESS, sp);
+
+ TEST_ASSERT(ret == 1, "KVM_SUBPAGES_GET_ACCESS failed.");
+
+ TEST_ASSERT(sp->access_map[0] == SUBPAGE_ACCESS_DEFAULT,
+ "subpage access didn't match.");
+ printf("get spp protection info: gfn = 0x%llx, access = 0x%x, "
+ "npages = %d\n", sp->gfn_base,
+ sp->access_map[0], sp->npages);
+
+ free(sp);
+ printf("got matched subpage permission vector.\n");
+ printf("expect VM exits caused by SPP below.\n");
+}
+
+void unset_spp(struct kvm_vm *vm)
+{
+ struct kvm_subpage *sp;
+ int len;
+
+ len = sizeof(*sp) + sizeof(__u32);
+ sp = malloc(len);
+ TEST_ASSERT(sp > 0, "Low memory 2!");
+ memset(sp, 0, len);
+
+ /* now unprotect the SPP to the page.*/
+ sp->npages = 1;
+ sp->gfn_base = pspp_start >> 12;
+ sp->access_map[0] = SUBPAGE_ACCESS_FULL;
+ ioctl(vm->fd, KVM_SUBPAGES_SET_ACCESS, sp);
+
+ printf("unset SPP protection at gfn: 0x%llx\n", sp->gfn_base);
+ printf("expect NO VM exits caused by SPP below.\n");
+ free(sp);
+}
+
+#define TEST_SYNC_FIELDS KVM_SYNC_X86_REGS
+
+void run_test(struct kvm_vm *vm, struct kvm_run *run)
+{
+ int loop;
+ int ept_fault = 0;
+ struct kvm_regs regs;
+
+ run->kvm_valid_regs = TEST_SYNC_FIELDS;
+ vcpu_run(vm, VCPU_ID);
+
+ for (loop = 0; loop < PAGE_SIZE / SUBPAGE_SIZE; loop++) {
+ /*
+ * if everything goes correctly, should get VM exit
+ * with KVM_EXIT_SPP.
+ */
+ TEST_ASSERT(run->exit_reason == KVM_EXIT_SPP,
+ "exit reason: %u (%s),\n", run->exit_reason,
+ exit_reason_str(run->exit_reason));
+ printf("%d - exit reason: %s\n", loop + 1,
+ exit_reason_str(run->exit_reason));
+ ept_fault++;
+
+ vcpu_regs_get(vm, VCPU_ID, &regs);
+
+ run->s.regs.regs.rip += run->spp.ins_len;
+
+ run->kvm_valid_regs = TEST_SYNC_FIELDS;
+ run->kvm_dirty_regs = KVM_SYNC_X86_REGS;
+
+ vcpu_run(vm, VCPU_ID);
+ }
+
+ printf("total EPT violation count: %d\n", ept_fault);
+}
+
+int main(int argc, char *argv[])
+{
+ struct kvm_vm *vm;
+ struct kvm_run *run;
+
+ prepare_test(&vm, &run);
+
+ setup_spp(vm);
+
+ run_test(vm, run);
+
+ unset_spp(vm);
+
+ vcpu_run(vm, VCPU_ID);
+
+ printf("completed SPP test successfully!\n");
+
+ kvm_vm_free(vm);
+
+ return 0;
+}
+
--
2.17.2