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Date: Thu, 30 Jul 2020 01:59:29 +0200
From: Alexander Graf <graf@...zon.com>
To: Paolo Bonzini <pbonzini@...hat.com>
CC: Jonathan Corbet <corbet@....net>,
Sean Christopherson <sean.j.christopherson@...el.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
"Joerg Roedel" <joro@...tes.org>,
KarimAllah Raslan <karahmed@...zon.de>, <kvm@...r.kernel.org>,
<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v2 3/3] KVM: selftests: Add test for user space MSR handling
Now that we have the ability to handle MSRs from user space and also to
select which ones we do want to prevent in-kernel KVM code from handling,
let's add a selftest to show case and verify the API.
Signed-off-by: Alexander Graf <graf@...zon.com>
---
tools/testing/selftests/kvm/Makefile | 1 +
.../selftests/kvm/x86_64/user_msr_test.c | 199 ++++++++++++++++++
2 files changed, 200 insertions(+)
create mode 100644 tools/testing/selftests/kvm/x86_64/user_msr_test.c
diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index 4a166588d99f..80d5c348354c 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -55,6 +55,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/vmx_set_nested_state_test
TEST_GEN_PROGS_x86_64 += x86_64/vmx_tsc_adjust_test
TEST_GEN_PROGS_x86_64 += x86_64/xss_msr_test
TEST_GEN_PROGS_x86_64 += x86_64/debug_regs
+TEST_GEN_PROGS_x86_64 += x86_64/user_msr_test
TEST_GEN_PROGS_x86_64 += clear_dirty_log_test
TEST_GEN_PROGS_x86_64 += demand_paging_test
TEST_GEN_PROGS_x86_64 += dirty_log_test
diff --git a/tools/testing/selftests/kvm/x86_64/user_msr_test.c b/tools/testing/selftests/kvm/x86_64/user_msr_test.c
new file mode 100644
index 000000000000..304a534e75c7
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86_64/user_msr_test.c
@@ -0,0 +1,199 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * tests for KVM_CAP_X86_USER_SPACE_MSR and KVM_ADD_MSR_ALLOWLIST
+ *
+ * Copyright (C) 2020, Amazon Inc.
+ *
+ * This is a functional test to verify that we can deflect MSR events
+ * into user space.
+ */
+#define _GNU_SOURCE /* for program_invocation_short_name */
+#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"
+
+#define VCPU_ID 5
+
+u32 msr_reads, msr_writes;
+
+struct range_desc {
+ struct kvm_msr_allowlist allow;
+ void (*populate)(struct kvm_msr_allowlist *range);
+};
+
+static void populate_c0000000_read(struct kvm_msr_allowlist *range)
+{
+ u8 *bitmap = range->bitmap;
+ u32 idx = MSR_SYSCALL_MASK & (KVM_MSR_ALLOWLIST_MAX_LEN - 1);
+
+ bitmap[idx / 8] &= ~(1 << (idx % 8));
+}
+
+static void populate_c0000000_write(struct kvm_msr_allowlist *range)
+{
+ u8 *bitmap = range->bitmap;
+ u32 idx = MSR_IA32_POWER_CTL & (KVM_MSR_ALLOWLIST_MAX_LEN - 1);
+
+ bitmap[idx / 8] &= ~(1 << (idx % 8));
+}
+
+struct range_desc ranges[] = {
+ {
+ .allow = {
+ .flags = KVM_MSR_ALLOW_READ | KVM_MSR_ALLOW_WRITE,
+ .base = 0x00000000,
+ .nmsrs = KVM_MSR_ALLOWLIST_MAX_LEN * BITS_PER_BYTE,
+ },
+ }, {
+ .allow = {
+ .flags = KVM_MSR_ALLOW_READ | KVM_MSR_ALLOW_WRITE,
+ .base = 0x40000000,
+ .nmsrs = KVM_MSR_ALLOWLIST_MAX_LEN * BITS_PER_BYTE,
+ },
+ }, {
+ .allow = {
+ .flags = KVM_MSR_ALLOW_READ,
+ .base = 0xc0000000,
+ .nmsrs = KVM_MSR_ALLOWLIST_MAX_LEN * BITS_PER_BYTE,
+ },
+ .populate = populate_c0000000_read,
+ }, {
+ .allow = {
+ .flags = KVM_MSR_ALLOW_WRITE,
+ .base = 0xc0000000,
+ .nmsrs = KVM_MSR_ALLOWLIST_MAX_LEN * BITS_PER_BYTE,
+ },
+ .populate = populate_c0000000_write,
+ },
+};
+
+static void guest_code(void)
+{
+ /* This goes into the in-kernel emulation */
+ wrmsr(MSR_SYSCALL_MASK, 0);
+
+ /* This goes into user space emulation */
+ GUEST_ASSERT(rdmsr(MSR_SYSCALL_MASK) == MSR_SYSCALL_MASK);
+
+ /* This goes into user space emulation */
+ wrmsr(MSR_IA32_POWER_CTL, 0x1234);
+
+ /* This goes into the in-kernel emulation */
+ rdmsr(MSR_IA32_POWER_CTL);
+
+ GUEST_DONE();
+}
+
+static int handle_ucall(struct kvm_vm *vm)
+{
+ struct ucall uc;
+
+ switch (get_ucall(vm, VCPU_ID, &uc)) {
+ case UCALL_ABORT:
+ TEST_FAIL("Guest assertion not met");
+ break;
+ case UCALL_DONE:
+ return 1;
+ default:
+ TEST_FAIL("Unknown ucall %lu", uc.cmd);
+ }
+
+ return 0;
+}
+
+static void handle_rdmsr(struct kvm_run *run)
+{
+ run->msr.data = run->msr.index;
+ run->msr.reply = 1;
+
+ msr_reads++;
+}
+
+static void handle_wrmsr(struct kvm_run *run)
+{
+ /* ignore */
+ run->msr.reply = 1;
+
+ msr_writes++;
+}
+
+int main(int argc, char *argv[])
+{
+ struct kvm_enable_cap cap = {
+ .cap = KVM_CAP_X86_USER_SPACE_MSR,
+ .args[0] = 1,
+ };
+ struct kvm_vm *vm;
+ struct kvm_run *run;
+ int rc;
+ int i;
+
+ /* Tell stdout not to buffer its content */
+ setbuf(stdout, NULL);
+
+ /* Create VM */
+ vm = vm_create_default(VCPU_ID, 0, guest_code);
+ vcpu_set_cpuid(vm, VCPU_ID, kvm_get_supported_cpuid());
+ run = vcpu_state(vm, VCPU_ID);
+
+ rc = kvm_check_cap(KVM_CAP_X86_USER_SPACE_MSR);
+ TEST_ASSERT(rc, "KVM_CAP_X86_USER_SPACE_MSR is available");
+ vm_enable_cap(vm, &cap);
+
+ rc = kvm_check_cap(KVM_CAP_ADD_MSR_ALLOWLIST);
+ TEST_ASSERT(rc, "KVM_CAP_ADD_MSR_ALLOWLIST is available");
+
+ /* Set up MSR allowlist */
+ for (i = 0; i < ARRAY_SIZE(ranges); i++) {
+ struct kvm_msr_allowlist *a = &ranges[i].allow;
+ u32 bitmap_size = a->nmsrs / BITS_PER_BYTE;
+ struct kvm_msr_allowlist *range = malloc(sizeof(*a) + bitmap_size);
+
+ TEST_ASSERT(range, "range alloc failed (%ld bytes)\n", sizeof(*a) + bitmap_size);
+
+ *range = *a;
+
+ /* Allow everything by default */
+ memset(range->bitmap, 0xff, bitmap_size);
+
+ if (ranges[i].populate)
+ ranges[i].populate(range);
+
+ vm_ioctl(vm, KVM_ADD_MSR_ALLOWLIST, range);
+ }
+
+ while (1) {
+ rc = _vcpu_run(vm, VCPU_ID);
+
+ TEST_ASSERT(rc == 0, "vcpu_run failed: %d\n", rc);
+
+ switch (run->exit_reason) {
+ case KVM_EXIT_RDMSR:
+ handle_rdmsr(run);
+ break;
+ case KVM_EXIT_WRMSR:
+ handle_wrmsr(run);
+ break;
+ case KVM_EXIT_IO:
+ if (handle_ucall(vm))
+ goto done;
+ break;
+ }
+
+ }
+
+ TEST_ASSERT(msr_reads == 1, "Handled 1 rdmsr in user space");
+ TEST_ASSERT(msr_writes == 1, "Handled 1 wrmsr in user space");
+
+done:
+ kvm_vm_free(vm);
+
+ return 0;
+}
--
2.17.1
Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879
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