Re: [PATCH 3/3 V6] selftest: KVM: Add intra host migration

[Marc Orr <marcorr@google.com>]

On Mon, Aug 30, 2021 at 2:29 PM Peter Gonda <pgonda@google.com> wrote:
>
> Adds testcases for intra host migration for SEV and SEV-ES. Also adds
> locking test to confirm no deadlock exists.
>
> ---
>  tools/testing/selftests/kvm/Makefile          |   1 +
>  .../selftests/kvm/x86_64/sev_vm_tests.c       | 152 ++++++++++++++++++
>  2 files changed, 153 insertions(+)
>  create mode 100644 tools/testing/selftests/kvm/x86_64/sev_vm_tests.c
>
> Signed-off-by: Peter Gonda <pgonda@google.com>
> Suggested-by: Sean Christopherson <seanjc@google.com>
> Cc: Marc Orr <marcorr@google.com>
> Cc: Sean Christopherson <seanjc@google.com>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: kvm@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
>
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index 5832f510a16c..de6e64d5c9c4 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -71,6 +71,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/tsc_msrs_test
>  TEST_GEN_PROGS_x86_64 += x86_64/vmx_pmu_msrs_test
>  TEST_GEN_PROGS_x86_64 += x86_64/xen_shinfo_test
>  TEST_GEN_PROGS_x86_64 += x86_64/xen_vmcall_test
> +TEST_GEN_PROGS_x86_64 += x86_64/sev_vm_tests
>  TEST_GEN_PROGS_x86_64 += access_tracking_perf_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/sev_vm_tests.c b/tools/testing/selftests/kvm/x86_64/sev_vm_tests.c
> new file mode 100644
> index 000000000000..50a770316628
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/x86_64/sev_vm_tests.c
> @@ -0,0 +1,150 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +#include <linux/kvm.h>
> +#include <linux/psp-sev.h>
> +#include <stdio.h>
> +#include <sys/ioctl.h>
> +#include <stdlib.h>
> +#include <errno.h>
> +#include <pthread.h>
> +
> +#include "test_util.h"
> +#include "kvm_util.h"
> +#include "processor.h"
> +#include "svm_util.h"
> +#include "kvm_util.h"
> +#include "kselftest.h"
> +#include "../lib/kvm_util_internal.h"
> +
> +#define SEV_DEV_PATH "/dev/sev"
> +
> +/*
> + * 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;
> +
> +       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;
> +}
> +
> +static void sev_ioctl(int fd, int cmd_id, void *data)
> +{
> +       struct kvm_sev_cmd cmd = { 0 };
> +       int ret;
> +
> +       TEST_ASSERT(cmd_id < KVM_SEV_NR_MAX, "Unknown SEV CMD : %d\n", cmd_id);
> +
> +       cmd.id = cmd_id;
> +       cmd.sev_fd = open_sev_dev_path_or_exit(0);
> +       cmd.data = (uint64_t)data;
> +       ret = ioctl(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);
> +}

nit: Since this function has two file descriptors, `fd` and
`cmd.sev_fd`, can we rename `fd` to `vm_fd`?

> +
> +static struct kvm_vm *sev_vm_create(bool es)
> +{
> +       struct kvm_vm *vm;
> +       struct kvm_sev_launch_start start = { 0 };
> +       int i;
> +
> +       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 < 3; ++i)

nit: Consider moving `3` to a macro, like `MAX_VCPU_IDX` or maybe
better defining something like `NUM_VCPUS` to be 4.

> +               vm_vcpu_add(vm, i);
> +       start.policy |= (es) << 2;
> +       sev_ioctl(vm->fd, KVM_SEV_LAUNCH_START, &start);
> +       if (es)
> +               sev_ioctl(vm->fd, KVM_SEV_LAUNCH_UPDATE_VMSA, NULL);
> +       return vm;
> +}
> +
> +static void test_sev_migrate_from(bool es)
> +{
> +       struct kvm_vm *vms[3];

If we create a `NUM_VCPUS` macro, then we can use it here.

> +       struct kvm_enable_cap cap = { 0 };
> +       int i;
> +
> +       for (i = 0; i < sizeof(vms) / sizeof(struct kvm_vm *); ++i)
> +               vms[i] = sev_vm_create(es);
> +
> +       cap.cap = KVM_CAP_VM_MIGRATE_ENC_CONTEXT_FROM;
> +       for (i = 0; i < sizeof(vms) / sizeof(struct kvm_vm *) - 1; ++i) {
> +               cap.args[0] = vms[i]->fd;
> +               vm_enable_cap(vms[i + 1], &cap);
> +       }

nit/optional: To me, the code would be more clear if we combined this
loop with the one above and guarded calling `vm_enable_cap()` with `if
(i > 0)`. Also, maybe we can initialize `cap` when it's declared.

     struct kvm_enable_cap cap = { .cap = KVM_CAP_VM_MIGRATE_ENC_CONTEXT_FROM };
     int i;

     for (i = 0; i < sizeof(vms) / sizeof(struct kvm_vm *); ++i) {
          vms[i] = sev_vm_create(es);
          if (i > 0)
               vm_enable_cap(vms[i], &cap);
     }

> +}
> +
> +#define LOCK_TESTING_THREADS 3

nit: Consider moving this macro to the top of the file.

> +
> +struct locking_thread_input {
> +       struct kvm_vm *vm;
> +       int source_fds[LOCK_TESTING_THREADS];
> +};
> +
> +static void *locking_test_thread(void *arg)
> +{
> +       struct kvm_enable_cap cap = { 0 };

Maybe:
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;
> +
> +       cap.cap = KVM_CAP_VM_MIGRATE_ENC_CONTEXT_FROM;

If we initialize the cap field during the declaration, then this line goes away.

> +
> +       for (i = 0; i < 1000; ++i) {
> +               j = input->source_fds[i % LOCK_TESTING_THREADS];
> +               cap.args[0] = input->source_fds[j];
> +               /*
> +                * Call IOCTL directly without checking return code. 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);

Should we use `vm_enable_cap()` here?

> +       }
> +}
> +
> +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) {
> +               input[i].vm = sev_vm_create(/* es= */ false);
> +               input[0].source_fds[i] = input[i].vm->fd;
> +       }
> +       memcpy(input[1].source_fds, input[0].source_fds,
> +              sizeof(input[1].source_fds));
> +       memcpy(input[2].source_fds, input[0].source_fds,
> +              sizeof(input[2].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);
> +}

I think this function/test case deserves a comment to capture some of
the conversation we had on the list that led to Sean suggesting this
test case. Speaking of which, should this test case have a
Suggested-by tag for Sean, since he suggested this test?

> +
> +int main(int argc, char *argv[])
> +{
> +       test_sev_migrate_from(/* es= */ false);
> +       test_sev_migrate_from(/* es= */ true);
> +       test_sev_migrate_locking();
> +       return 0;
> +}
> --
> 2.33.0.259.gc128427fd7-goog
>

Nice test!