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Re: [Qemu-devel] [PATCH v3 for-2.11 1/3] tpm_emulator: Add a caching lay
From: |
Marc-André Lureau |
Subject: |
Re: [Qemu-devel] [PATCH v3 for-2.11 1/3] tpm_emulator: Add a caching layer for the TPM Established flag |
Date: |
Wed, 15 Nov 2017 00:40:22 +0100 |
Hi
On Tue, Nov 14, 2017 at 10:52 PM, Stefan Berger
<address@hidden> wrote:
> Add a caching layer for the TPM established flag so that we don't
> need to go to the emulator every time the flag is read by accessing
> the REG_ACCESS register.
What's the impact? Isn't this just a "small" optimization? Iotw, why
is this for-2.11?
> Signed-off-by: Stefan Berger <address@hidden>
>
> v1->v2:
> - move the caching to the backend layer since detecting the
> TPM 1.2 TSC_ResetEstablishmentBit() command is easier to do
> here.
> ---
> hw/tpm/tpm_emulator.c | 17 ++++++++++++++---
> 1 file changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/hw/tpm/tpm_emulator.c b/hw/tpm/tpm_emulator.c
> index e1a6810..b293db7 100644
> --- a/hw/tpm/tpm_emulator.c
> +++ b/hw/tpm/tpm_emulator.c
> @@ -73,6 +73,9 @@ typedef struct TPMEmulator {
> Error *migration_blocker;
>
> QemuMutex mutex;
> +
> + unsigned int established_flag:1;
> + unsigned int established_flag_cached:1;
> } TPMEmulator;
>
>
> @@ -287,16 +290,22 @@ static bool
> tpm_emulator_get_tpm_established_flag(TPMBackend *tb)
> TPMEmulator *tpm_emu = TPM_EMULATOR(tb);
> ptm_est est;
>
> - DPRINTF("%s", __func__);
> + if (tpm_emu->established_flag_cached) {
> + return tpm_emu->established_flag;
> + }
> +
> if (tpm_emulator_ctrlcmd(tpm_emu, CMD_GET_TPMESTABLISHED, &est,
> 0, sizeof(est)) < 0) {
> error_report("tpm-emulator: Could not get the TPM established flag:
> %s",
> strerror(errno));
> return false;
> }
> - DPRINTF("established flag: %0x", est.u.resp.bit);
> + DPRINTF("got established flag: %0x", est.u.resp.bit);
> +
> + tpm_emu->established_flag_cached = 1;
> + tpm_emu->established_flag = (est.u.resp.bit != 0);
>
> - return (est.u.resp.bit != 0);
> + return tpm_emu->established_flag;
> }
>
> static int tpm_emulator_reset_tpm_established_flag(TPMBackend *tb,
> @@ -327,6 +336,8 @@ static int
> tpm_emulator_reset_tpm_established_flag(TPMBackend *tb,
> return -1;
> }
>
> + tpm_emu->established_flag_cached = 0;
> +
> return 0;
> }
>
> --
> 2.5.5
>
--
Marc-André Lureau
[Qemu-devel] [PATCH v3 for-2.11 3/3] tpm_tis: Return 0 for every register in case of failure mode, Stefan Berger, 2017/11/14
[Qemu-devel] [PATCH v3 for-2.11 2/3] tpm_tis: Return TPM_VERSION_UNSPEC in case of BE failure, Stefan Berger, 2017/11/14