Re: [Qemu-devel] [PATCH v2 09/13] target/i386: sev: add support to encrypt the outgoing page

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Singh, Brijesh (brijesh.singh@amd.com) wrote:
> The sev_save_outgoing_page() provide the implementation to encrypt the
> guest private pages during the transit. The routines uses the SEND_START
> command to create the outgoing encryption context on the first call then
> uses the SEND_UPDATE_DATA command to encrypt the data before writing it
> to the socket. While encrypting the data SEND_UPDATE_DATA produces some
> metadata (e.g MAC, IV). The metadata is also sent to the target machine.
> After migration is completed, we issue the SEND_FINISH command to transition
> the SEV guest state from sending to unrunnable state.
> 
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
>  accel/kvm/kvm-all.c      |   1 +
>  target/i386/sev.c        | 229 +++++++++++++++++++++++++++++++++++++++
>  target/i386/sev_i386.h   |   2 +
>  target/i386/trace-events |   3 +
>  4 files changed, 235 insertions(+)
> 
> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index c935e9366c..a9fb447248 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -1792,6 +1792,7 @@ static int kvm_init(MachineState *ms)
>          }
>  
>          kvm_state->memcrypt_encrypt_data = sev_encrypt_data;
> +        kvm_state->memcrypt_save_outgoing_page = sev_save_outgoing_page;
>      }
>  
>      ret = kvm_arch_init(ms, s);
> diff --git a/target/i386/sev.c b/target/i386/sev.c
> index 6c902d0be8..28b36c8035 100644
> --- a/target/i386/sev.c
> +++ b/target/i386/sev.c
> @@ -27,6 +27,8 @@
>  #include "sysemu/sysemu.h"
>  #include "trace.h"
>  #include "migration/blocker.h"
> +#include "migration/qemu-file.h"
> +#include "migration/misc.h"
>  
>  #define DEFAULT_GUEST_POLICY    0x1 /* disable debug */
>  #define DEFAULT_SEV_DEVICE      "/dev/sev"
> @@ -718,6 +720,39 @@ sev_vm_state_change(void *opaque, int running, RunState state)
>      }
>  }
>  
> +static void
> +sev_send_finish(void)
> +{
> +    int ret, error;
> +
> +    trace_kvm_sev_send_finish();
> +    ret = sev_ioctl(sev_state->sev_fd, KVM_SEV_SEND_FINISH, 0, &error);
> +    if (ret) {
> +        error_report("%s: LAUNCH_FINISH ret=%d fw_error=%d '%s'",

why LAUNCH?

> +                     __func__, ret, error, fw_error_to_str(error));
> +    }
> +
> +    sev_set_guest_state(SEV_STATE_RUNNING);
> +}
> +
> +static void
> +sev_migration_state_notifier(Notifier *notifier, void *data)
> +{
> +    MigrationState *s = data;
> +
> +    if (migration_has_finished(s) ||
> +        migration_in_postcopy_after_devices(s) ||
> +        migration_has_failed(s)) {
> +        if (sev_check_state(SEV_STATE_SEND_UPDATE)) {
> +            sev_send_finish();
> +        }

I don't quite understand SEV_SEND_FINISH; is it just terminating the
migration process or is it actually making the VM unrunnable?
I'm interested in what the behaviour is on a failed migration - do
we lose both VMs or do we potentialyl have a memory clone?
(Neither are pretty!)

> +    }
> +}
> +
> +static Notifier sev_migration_state_notify = {
> +    .notify = sev_migration_state_notifier,
> +};
> +
>  void *
>  sev_guest_init(const char *id)
>  {
> @@ -804,6 +839,7 @@ sev_guest_init(const char *id)
>      ram_block_notifier_add(&sev_ram_notifier);
>      qemu_add_machine_init_done_notifier(&sev_machine_done_notify);
>      qemu_add_vm_change_state_handler(sev_vm_state_change, s);
> +    add_migration_state_change_notifier(&sev_migration_state_notify);
>  
>      return s;
>  err:
> @@ -836,6 +872,199 @@ void sev_set_migrate_info(const char *pdh, const char *plat_cert,
>      s->amd_cert = g_base64_decode(amd_cert, &s->amd_cert_len);
>  }
>  
> +static int
> +sev_get_send_session_length(void)
> +{
> +    int ret, fw_err = 0;
> +    struct kvm_sev_send_start *start;
> +
> +    start = g_new0(struct kvm_sev_send_start, 1);

These are tiny structures; they may as well be on the stack rather than
allocating/freeing them.

> +    ret = sev_ioctl(sev_state->sev_fd, KVM_SEV_SEND_START, start, &fw_err);
> +    if (fw_err != SEV_RET_INVALID_LEN) {
> +        ret = -1;
> +        error_report("%s: failed to get session length ret=%d fw_error=%d '%s'",
> +                     __func__, ret, fw_err, fw_error_to_str(fw_err));
> +        goto err;
> +    }
> +
> +    ret = start->session_len;
> +err:
> +    g_free(start);
> +    return ret;
> +}
> +
> +static int
> +sev_send_start(SEVState *s, QEMUFile *f, uint64_t *bytes_sent)
> +{
> +    gsize pdh_len = 0, plat_cert_len;
> +    int session_len, ret, fw_error;
> +    struct kvm_sev_send_start *start;
> +    guchar *pdh = NULL, *plat_cert = NULL, *session = NULL;
> +
> +    if (!s->remote_pdh || !s->remote_plat_cert) {
> +        error_report("%s: missing remote PDH or PLAT_CERT", __func__);
> +        return 1;
> +    }
> +
> +    start = g_new0(struct kvm_sev_send_start, 1);
> +
> +    start->pdh_cert_uaddr = (unsigned long) s->remote_pdh;
> +    start->pdh_cert_len = s->remote_pdh_len;
> +
> +    start->plat_cert_uaddr = (unsigned long)s->remote_plat_cert;
> +    start->plat_cert_len = s->remote_plat_cert_len;
> +
> +    start->amd_cert_uaddr = (unsigned long)s->amd_cert;

Should these actually be case via a uint64_t ? They're explicitly
64bit - you might have to go via a uintptr_t to make some compilers
happy?

> +    start->amd_cert_len = s->amd_cert_len;
> +
> +    /* get the session length */
> +    session_len = sev_get_send_session_length();
> +    if (session_len < 0) {
> +        ret = 1;
> +        goto err;
> +    }
> +
> +    session = g_new0(guchar, session_len);
> +    start->session_uaddr = (unsigned long)session;
> +    start->session_len = session_len;
> +
> +    /* Get our PDH certificate */
> +    ret = sev_get_pdh_info(s->sev_fd, &pdh, &pdh_len,
> +                           &plat_cert, &plat_cert_len);
> +    if (ret) {
> +        error_report("Failed to get our PDH cert");
> +        goto err;
> +    }
> +
> +    trace_kvm_sev_send_start(start->pdh_cert_uaddr, start->pdh_cert_len,
> +                             start->plat_cert_uaddr, start->plat_cert_len,
> +                             start->amd_cert_uaddr, start->amd_cert_len);
> +
> +    ret = sev_ioctl(s->sev_fd, KVM_SEV_SEND_START, start, &fw_error);
> +    if (ret < 0) {
> +        error_report("%s: SEND_START ret=%d fw_error=%d '%s'",
> +                __func__, ret, fw_error, fw_error_to_str(fw_error));
> +        goto err;
> +    }
> +
> +    qemu_put_be32(f, start->policy);
> +    qemu_put_be32(f, pdh_len);
> +    qemu_put_buffer(f, (uint8_t *)pdh, pdh_len);
> +    qemu_put_be32(f, start->session_len);
> +    qemu_put_buffer(f, (uint8_t *)start->session_uaddr, start->session_len);
> +    *bytes_sent = 12 + pdh_len + start->session_len;
> +
> +    sev_set_guest_state(SEV_STATE_SEND_UPDATE);
> +
> +err:
> +    g_free(start);
> +    g_free(pdh);
> +    g_free(plat_cert);
> +    return ret;
> +}
> +
> +static int
> +sev_send_get_packet_len(int *fw_err)
> +{
> +    int ret;
> +    struct kvm_sev_send_update_data *update;
> +
> +    update = g_malloc0(sizeof(*update));
> +    if (!update) {
> +        return -1;
> +    }
> +
> +    ret = sev_ioctl(sev_state->sev_fd, KVM_SEV_SEND_UPDATE_DATA, update, fw_err);
> +    if (*fw_err != SEV_RET_INVALID_LEN) {
> +        ret = -1;
> +        error_report("%s: failed to get session length ret=%d fw_error=%d '%s'",
> +                    __func__, ret, *fw_err, fw_error_to_str(*fw_err));
> +        goto err;
> +    }
> +
> +    ret = update->hdr_len;
> +
> +err:
> +    g_free(update);
> +    return ret;
> +}
> +
> +static int
> +sev_send_update_data(SEVState *s, QEMUFile *f, uint8_t *ptr, uint32_t size,
> +                     uint64_t *bytes_sent)
> +{
> +    int ret, fw_error;
> +    guchar *trans;
> +    struct kvm_sev_send_update_data *update;
> +
> +    /* If this is first call then query the packet header bytes and allocate
> +     * the packet buffer.
> +     */
> +    if (!s->send_packet_hdr) {
> +        s->send_packet_hdr_len = sev_send_get_packet_len(&fw_error);
> +        if (s->send_packet_hdr_len < 1) {
> +            error_report("%s: SEND_UPDATE fw_error=%d '%s'",
> +                    __func__, fw_error, fw_error_to_str(fw_error));
> +            return 1;
> +        }
> +
> +        s->send_packet_hdr = g_new(gchar, s->send_packet_hdr_len);

When does this get freed?

> +    }
> +
> +    update = g_new0(struct kvm_sev_send_update_data, 1);
> +
> +    /* allocate transport buffer */
> +    trans = g_new(guchar, size);
> +
> +    update->hdr_uaddr = (unsigned long)s->send_packet_hdr;
> +    update->hdr_len = s->send_packet_hdr_len;
> +    update->guest_uaddr = (unsigned long)ptr;
> +    update->guest_len = size;
> +    update->trans_uaddr = (unsigned long)trans;
> +    update->trans_len = size;
> +
> +    trace_kvm_sev_send_update_data(ptr, trans, size);
> +
> +    ret = sev_ioctl(s->sev_fd, KVM_SEV_SEND_UPDATE_DATA, update, &fw_error);
> +    if (ret) {
> +        error_report("%s: SEND_UPDATE_DATA ret=%d fw_error=%d '%s'",
> +                __func__, ret, fw_error, fw_error_to_str(fw_error));
> +        goto err;
> +    }
> +
> +    qemu_put_be32(f, update->hdr_len);
> +    qemu_put_buffer(f, (uint8_t *)update->hdr_uaddr, update->hdr_len);
> +    *bytes_sent = 4 + update->hdr_len;
> +
> +    qemu_put_be32(f, update->trans_len);
> +    qemu_put_buffer(f, (uint8_t *)update->trans_uaddr, update->trans_len);
> +    *bytes_sent += (4 + update->trans_len);
> +
> +err:
> +    g_free(trans);
> +    g_free(update);
> +    return ret;
> +}
> +
> +int sev_save_outgoing_page(void *handle, QEMUFile *f, uint8_t *ptr,
> +                           uint32_t sz, uint64_t *bytes_sent)
> +{
> +    SEVState *s = sev_state;
> +
> +    /*
> +     * If this is a first buffer then create outgoing encryption context
> +     * and write our PDH, policy and session data.
> +     */
> +    if (!sev_check_state(SEV_STATE_SEND_UPDATE) &&
> +        sev_send_start(s, f, bytes_sent)) {
> +        error_report("Failed to create outgoing context");
> +        return 1;
> +    }
> +
> +    return sev_send_update_data(s, f, ptr, sz, bytes_sent);
> +}
> +
>  static void
>  sev_register_types(void)
>  {
> diff --git a/target/i386/sev_i386.h b/target/i386/sev_i386.h
> index 3f3449b346..2fdca5190d 100644
> --- a/target/i386/sev_i386.h
> +++ b/target/i386/sev_i386.h
> @@ -88,6 +88,8 @@ struct SEVState {
>      size_t remote_plat_cert_len;
>      guchar *amd_cert;
>      size_t amd_cert_len;
> +    gchar *send_packet_hdr;
> +    size_t send_packet_hdr_len;
>  };
>  
>  typedef struct SEVState SEVState;
> diff --git a/target/i386/trace-events b/target/i386/trace-events
> index 789c700d4a..b41516cf9f 100644
> --- a/target/i386/trace-events
> +++ b/target/i386/trace-events
> @@ -15,3 +15,6 @@ kvm_sev_launch_start(int policy, void *session, void *pdh) "policy 0x%x session
>  kvm_sev_launch_update_data(void *addr, uint64_t len) "addr %p len 0x%" PRIu64
>  kvm_sev_launch_measurement(const char *value) "data %s"
>  kvm_sev_launch_finish(void) ""
> +kvm_sev_send_start(uint64_t pdh, int l1, uint64_t plat, int l2, uint64_t amd, int l3) "pdh 0x%" PRIx64 " len %d plat 0x%" PRIx64 " len %d amd 0x%" PRIx64 " len %d"
> +kvm_sev_send_update_data(void *src, void *dst, int len) "guest %p trans %p len %d"
> +kvm_sev_send_finish(void) ""
> -- 
> 2.17.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK