Re: [Qemu-devel] [PATCH v3 10/13] tpm: Introduce condition in TPM backend for notification

[Stefan Berger <stefanb@linux.vnet.ibm.com>]

On 11/10/2017 09:11 AM, Stefan Berger wrote:
> TPM backends will suspend independently of the frontends. Also
> here we need to be able to wait for the TPM command to have been
> completely processed.
>
> Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
> ---
>   backends/tpm.c               | 19 +++++++++++++++++++
>   include/sysemu/tpm_backend.h | 14 ++++++++++++++
>   2 files changed, 33 insertions(+)
>
> diff --git a/backends/tpm.c b/backends/tpm.c
> index 91222c5..bf0e120 100644
> --- a/backends/tpm.c
> +++ b/backends/tpm.c
> @@ -20,6 +20,14 @@
>   #include "qemu/thread.h"
>   #include "qemu/main-loop.h"
>
> +void tpm_backend_cmd_completed(TPMBackend *s)
> +{
> +    qemu_mutex_lock(&s->state_lock);
> +    s->tpm_busy = false;
> +    qemu_cond_signal(&s->cmd_complete);
> +    qemu_mutex_unlock(&s->state_lock);
> +}
> +
>   static void tpm_backend_request_completed_bh(void *opaque)
>   {
>       TPMBackend *s = TPM_BACKEND(opaque);
> @@ -36,6 +44,9 @@ static void tpm_backend_worker_thread(gpointer data, gpointer user_data)
>       k->handle_request(s, (TPMBackendCmd *)data);
>
>       qemu_bh_schedule(s->bh);
> +
> +    /* result delivered */
> +    tpm_backend_cmd_completed(s);
>   }
>
>   static void tpm_backend_thread_end(TPMBackend *s)
> @@ -64,6 +75,10 @@ int tpm_backend_init(TPMBackend *s, TPMIf *tpmif, Error **errp)
>       object_ref(OBJECT(tpmif));
>
>       s->had_startup_error = false;
> +    s->tpm_busy = false;
> +
> +    qemu_mutex_init(&s->state_lock);
> +    qemu_cond_init(&s->cmd_complete);
>
>       return 0;
>   }
> @@ -93,6 +108,10 @@ bool tpm_backend_had_startup_error(TPMBackend *s)
>
>   void tpm_backend_deliver_request(TPMBackend *s, TPMBackendCmd *cmd)
>   {
> +    qemu_mutex_lock(&s->state_lock);
> +    s->tpm_busy = true;
> +    qemu_mutex_unlock(&s->state_lock);
> +
>       g_thread_pool_push(s->thread_pool, cmd, NULL);
>   }
>
> diff --git a/include/sysemu/tpm_backend.h b/include/sysemu/tpm_backend.h
> index 0d6c994..39598e3 100644
> --- a/include/sysemu/tpm_backend.h
> +++ b/include/sysemu/tpm_backend.h
> @@ -18,6 +18,7 @@
>   #include "qapi-types.h"
>   #include "qemu/option.h"
>   #include "sysemu/tpm.h"
> +#include "qemu/thread.h"
>
>   #define TYPE_TPM_BACKEND "tpm-backend"
>   #define TPM_BACKEND(obj) \
> @@ -53,6 +54,10 @@ struct TPMBackend {
>       char *id;
>
>       QLIST_ENTRY(TPMBackend) list;
> +
> +    QemuMutex state_lock;

This lock only locks the tpm_busy flag. So maybe I should rename it to 
tpm_busy_lock. It's not meant to be a general state lock.

    Stefan

> +    QemuCond cmd_complete; /* signaled once tpm_busy is false */
> +    bool tpm_busy;
>   };
>
>   struct TPMBackendClass {
> @@ -206,6 +211,15 @@ size_t tpm_backend_get_buffer_size(TPMBackend *s);
>    */
>   TPMInfo *tpm_backend_query_tpm(TPMBackend *s);
>
> +/**
> + * tpm_backend_cmd_completed:
> + * @s: the backend
> + *
> + * Mark the backend as not busy and notify anyone interested
> + * in the state changed
> + */
> +void tpm_backend_cmd_completed(TPMBackend *s);
> +
>   TPMBackend *qemu_find_tpm_be(const char *id);
>
>   #endif