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Message-ID: <YTuS3iHN7GgK4oQr@google.com>
Date: Fri, 10 Sep 2021 17:16:14 +0000
From: Sean Christopherson <seanjc@...gle.com>
To: Peter Gonda <pgonda@...gle.com>
Cc: kvm@...r.kernel.org, Marc Orr <marcorr@...gle.com>,
David Rientjes <rientjes@...gle.com>,
Brijesh Singh <brijesh.singh@....com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3 V7] selftest: KVM: Add intra host migration tests
On Thu, Sep 02, 2021, Peter Gonda wrote:
> +/*
> + * Open SEV_DEV_PATH if available, otherwise exit the entire program.
> + *
> + * Input Args:
> + * flags - The flags to pass when opening SEV_DEV_PATH.
> + *
> + * Return:
> + * The opened file descriptor of /dev/sev.
> + */
> +static int open_sev_dev_path_or_exit(int flags)
> +{
> + static int fd;
> +
> + if (fd != 0)
> + return fd;
Caching the file here is unnecessary, it's used in exactly one function.
> + fd = open(SEV_DEV_PATH, flags);
> + if (fd < 0) {
> + print_skip("%s not available, is SEV not enabled? (errno: %d)",
> + SEV_DEV_PATH, errno);
> + exit(KSFT_SKIP);
> + }
> +
> + return fd;
> +}
Rather than copy-paste _open_kvm_dev_path_or_exit(), it's probably worth factoring
out a helper in a separate patch, e.g.
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 10a8ed691c66..06a6c04010fb 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -31,6 +31,19 @@ static void *align(void *x, size_t size)
return (void *) (((size_t) x + mask) & ~mask);
}
+int open_path_or_exit(const char *path, int flags)
+{
+ int fd;
+
+ fd = open(path, flags);
+ if (fd < 0) {
+ print_skip("%s not available (errno: %d)", path, errno);
+ exit(KSFT_SKIP);
+ }
+
+ return fd;
+}
+
/*
* Open KVM_DEV_PATH if available, otherwise exit the entire program.
*
@@ -42,16 +55,7 @@ static void *align(void *x, size_t size)
*/
static int _open_kvm_dev_path_or_exit(int flags)
{
- int fd;
-
- fd = open(KVM_DEV_PATH, flags);
- if (fd < 0) {
- print_skip("%s not available, is KVM loaded? (errno: %d)",
- KVM_DEV_PATH, errno);
- exit(KSFT_SKIP);
- }
-
- return fd;
+ return open_path_or_exit(KVM_DEV_PATH, flags);
}
int open_kvm_dev_path_or_exit(void)
> +
> +static void sev_ioctl(int vm_fd, int cmd_id, void *data)
> +{
> + struct kvm_sev_cmd cmd = {
> + .id = cmd_id,
> + .data = (uint64_t)data,
> + .sev_fd = open_sev_dev_path_or_exit(0),
> + };
> + int ret;
> +
> + TEST_ASSERT(cmd_id < KVM_SEV_NR_MAX && cmd_id >= 0,
> + "Unknown SEV CMD : %d\n", cmd_id);
LOL, I like sanity checks, but asserting that the test itself isn't horrendously
broken is a bit much. And someone manages to screw up that badly, the ioctl()
below will fail.
> + ret = ioctl(vm_fd, KVM_MEMORY_ENCRYPT_OP, &cmd);
> + TEST_ASSERT((ret == 0 || cmd.error == SEV_RET_SUCCESS),
> + "%d failed: return code: %d, errno: %d, fw error: %d",
> + cmd_id, ret, errno, cmd.error);
> +}
> +
> +static struct kvm_vm *sev_vm_create(bool es)
> +{
> + struct kvm_vm *vm;
> + struct kvm_sev_launch_start start = { 0 };
> + int i;
Rather than cache /dev/sev in a helper, you can do:
int sev_fd = open_path_or_exit(SEV_DEV_PATH, 0);
sev_ioctl(vm, sev_fd, ...);
> + vm = vm_create(VM_MODE_DEFAULT, 0, O_RDWR);
> + sev_ioctl(vm->fd, es ? KVM_SEV_ES_INIT : KVM_SEV_INIT, NULL);
> + for (i = 0; i < MIGRATE_TEST_NUM_VCPUS; ++i)
> + vm_vcpu_add(vm, i);
> + start.policy |= (es) << 2;
I had to go spelunking to confirm this is the "ES" policy, please do:
if (es)
start.policy |= SEV_POLICY_ES;
> + sev_ioctl(vm->fd, KVM_SEV_LAUNCH_START, &start);
> + if (es)
> + sev_ioctl(vm->fd, KVM_SEV_LAUNCH_UPDATE_VMSA, NULL);
And with sev_fd scoped to this function:
close(sev_fd);
which I think is legal?
> + return vm;
> +}
> +
> +static void test_sev_migrate_from(bool es)
> +{
> + struct kvm_vm *vms[MIGRATE_TEST_VMS];
Prefix this and LOCK_TESTING_THREAD with NR_ so that it's clear these are arbitrary
numbers of things. And I guess s/MIGRATE_TEST_NUM_VCPUS/NR_MIGRATE_TEST_VCPUS to
be consistent.
> + struct kvm_enable_cap cap = {
> + .cap = KVM_CAP_VM_MIGRATE_ENC_CONTEXT_FROM
> + };
> + int i;
> +
> + for (i = 0; i < MIGRATE_TEST_VMS; ++i) {
> + vms[i] = sev_vm_create(es);
It doesn't really matter, but closing these fds tests that KVM doesn't explode
when VMs are destroyed without the process exiting.
> + if (i > 0) {
> + cap.args[0] = vms[i - 1]->fd;
> + vm_enable_cap(vms[i], &cap);
> + }
> + }
For giggles, we can also test migrating back (with some feedback from below
mixed in):
/* Initial migration from the src to the first dst. */
sev_migrate_from(dst_vms[0]->fd, src_vm->fd);
for (i = 1; i < NR_MIGRATE_TEST_VMS; i++)
sev_migrate_from(vms[i]->fd, vms[i - 1]->fd);
/* Migrate the guest back to the original VM. */
sev_migrate_from(src_vm->fd, dst_vms[NR_MIGRATE_TEST_VMS - 1]->fd);
> +}
> +
> +struct locking_thread_input {
> + struct kvm_vm *vm;
> + int source_fds[LOCK_TESTING_THREADS];
> +};
> +
> +static void *locking_test_thread(void *arg)
> +{
> + /*
> + * This test case runs a number of threads all trying to use the intra
> + * host migration ioctls. This tries to detect if a deadlock exists.
> + */
> + struct kvm_enable_cap cap = {
> + .cap = KVM_CAP_VM_MIGRATE_ENC_CONTEXT_FROM
> + };
> + int i, j;
> + struct locking_thread_input *input = (struct locking_test_thread *)arg;
> +
> + for (i = 0; i < LOCK_TESTING_ITERATIONS; ++i) {
> + j = input->source_fds[i % LOCK_TESTING_THREADS];
> + cap.args[0] = input->source_fds[j];
This looks wrong, it's indexing source_fds with a value from source_fds. Did
you intend?
j = i % LOCK_TESTING_THREADS;
cap.args[0] = input->source_fds[j];
> + /*
> + * Call IOCTL directly without checking return code or
> + * asserting. We are * simply trying to confirm there is no
> + * deadlock from userspace * not check correctness of
> + * migration here.
> + */
> + ioctl(input->vm->fd, KVM_ENABLE_CAP, &cap);
For readability and future extensibility, I'd say create a single helper and use
it even in the happy case, e.g.
static int __sev_migrate_from(int dst_fd, int src_fd)
{
struct kvm_enable_cap cap = {
.cap = KVM_CAP_VM_MIGRATE_ENC_CONTEXT_FROM,
.args = { src_fd } // No idea if this is correct syntax
};
return ioctl(dst_fd, KVM_ENABLE_CAP, &cap);
}
static void sev_migrate_from(...)
{
ret = __sev_migrate_from(...);
TEST_ASSERT(!ret, "Migration failed, blah blah blah");
}
> + }
> +}
> +
> +static void test_sev_migrate_locking(void)
> +{
> + struct locking_thread_input input[LOCK_TESTING_THREADS];
> + pthread_t pt[LOCK_TESTING_THREADS];
> + int i;
> +
> + for (i = 0; i < LOCK_TESTING_THREADS; ++i) {
With a bit of refactoring, the same VMs from the happy case can be reused for
the locking test, and we can also get concurrent SEV+SEV-ES migration (see below).
> + input[i].vm = sev_vm_create(/* es= */ false);
> + input[0].source_fds[i] = input[i].vm->fd;
> + }
> + for (i = 1; i < LOCK_TESTING_THREADS; ++i)
> + memcpy(input[i].source_fds, input[0].source_fds,
> + sizeof(input[i].source_fds));
> +
> + for (i = 0; i < LOCK_TESTING_THREADS; ++i)
> + pthread_create(&pt[i], NULL, locking_test_thread, &input[i]);
> +
> + for (i = 0; i < LOCK_TESTING_THREADS; ++i)
> + pthread_join(pt[i], NULL);
> +}
> +
> +int main(int argc, char *argv[])
> +{
> + test_sev_migrate_from(/* es= */ false);
> + test_sev_migrate_from(/* es= */ true);
> + test_sev_migrate_locking();
With a little refactoring, this can add other tests, e.g. illegal dst. Assuming
KVM requires the dst to be !SEV, SEV and SEV-ES can use the same set of destination
VMs. And the locking test can take 'em all. E.g. something like:
struct kvm_vm *sev_vm, *sev_es_vm;
sev_vm = sev_vm_create(false);
sev_es_vm = sev_vm_create(true);
for (i = 0; i < NR_MIGRATE_TEST_VMS; i++)
dst_vms[i] = sev_dst_vm_create();
test_sev_migrate_from(sev_vms, dst_vms);
test_sev_migrate_from(sev_es_vms, dst_vms);
ret = __sev_migrate_from(sev_es_vms[0], sev_vms[0]);
TEST_ASSERT(ret == -EINVAL, ...);
ret = __sev_migrate_from(sev_vms[0], sev_es_vms[0]);
TEST_ASSERT(ret == -EINVAL, ...);
ret = __sev_migrate_from(dst_vms[0], dst_vms[1]);
TEST_ASSERT(ret == -EINVAL, ....);
test_sev_migrate_locking(sev_vm, sev_es_vm, dst_vms);
> + return 0;
> +}
> --
> 2.33.0.153.gba50c8fa24-goog
>
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