Re: [Qemu-devel] [PATCH] tpm: Add a caching layer for the TPM Established flag

[Stefan Berger]

On 11/08/2017 02:45 PM, Stefan Berger wrote:
> Add a caching layer for the TPM established flag so that we don't
> need to go to the backend every time the flag is read by accessing
> the REG_ACCESS register.

The v2 I just sent moves this to the tpm_emulator.

    Stefan

> Signed-off-by: Stefan Berger <address@hidden>
> ---
>   hw/tpm/tpm_tis.c | 27 +++++++++++++++++++++++++--
>   1 file changed, 25 insertions(+), 2 deletions(-)
>
> diff --git a/hw/tpm/tpm_tis.c b/hw/tpm/tpm_tis.c
> index 7402528..6b81bbf 100644
> --- a/hw/tpm/tpm_tis.c
> +++ b/hw/tpm/tpm_tis.c
> @@ -95,6 +95,9 @@ struct TPMState {
>       char *backend;
>       TPMBackend *be_driver;
>       TPMVersion be_tpm_version;
> +
> +    unsigned int established_flag:1;
> +    unsigned int established_flag_cached:1;
>   };
>
>   #define TPM(obj) OBJECT_CHECK(TPMState, (obj), TYPE_TPM_TIS)
> @@ -529,6 +532,26 @@ static void tpm_tis_dump_state(void *opaque, hwaddr addr)
>   }
>   #endif
>
> +static void tpm_tis_reset_tpm_established_flag(TPMState *s,
> +                                               uint8_t locty)
> +{
> +    s->established_flag_cached = 0;
> +
> +    tpm_backend_reset_tpm_established_flag(s->be_driver, locty);
> +}
> +
> +static unsigned int tpm_tis_get_tpm_established_flag(TPMState *s)
> +{
> +    if (s->established_flag_cached) {
> +        return s->established_flag;
> +    }
> +
> +    s->established_flag = !tpm_backend_get_tpm_established_flag(s->be_driver);
> +    s->established_flag_cached = 1;
> +
> +    return s->established_flag;
> +}
> +
>   /*
>    * Read a register of the TIS interface
>    * See specs pages 33-63 for description of the registers
> @@ -556,7 +579,7 @@ static uint64_t tpm_tis_mmio_read(void *opaque, hwaddr addr,
>           if (tpm_tis_check_request_use_except(s, locty)) {
>               val |= TPM_TIS_ACCESS_PENDING_REQUEST;
>           }
> -        val |= !tpm_backend_get_tpm_established_flag(s->be_driver);
> +        val |= tpm_tis_get_tpm_established_flag(s);
>           break;
>       case TPM_TIS_REG_INT_ENABLE:
>           val = s->loc[locty].inte;
> @@ -840,7 +863,7 @@ static void tpm_tis_mmio_write(void *opaque, hwaddr addr,
>
>               if (val & TPM_TIS_STS_RESET_ESTABLISHMENT_BIT) {
>                   if (locty == 3 || locty == 4) {
> -                    tpm_backend_reset_tpm_established_flag(s->be_driver, 
> locty);
> +                    tpm_tis_reset_tpm_established_flag(s, locty);
>                   }
>               }
>           }