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  • James Bottomley's avatar
    tpm: add retry logic · e2fb992d
    James Bottomley authored
    
    
    TPM2 can return TPM2_RC_RETRY to any command and when it does we get
    unexpected failures inside the kernel that surprise users (this is
    mostly observed in the trusted key handling code).  The UEFI 2.6 spec
    has advice on how to handle this:
    
        The firmware SHALL not return TPM2_RC_RETRY prior to the completion
        of the call to ExitBootServices().
    
        Implementer’s Note: the implementation of this function should check
        the return value in the TPM response and, if it is TPM2_RC_RETRY,
        resend the command. The implementation may abort if a sufficient
        number of retries has been done.
    
    So we follow that advice in our tpm_transmit() code using
    TPM2_DURATION_SHORT as the initial wait duration and
    TPM2_DURATION_LONG as the maximum wait time.  This should fix all the
    in-kernel use cases and also means that user space TSS implementations
    don't have to have their own retry handling.
    
    Signed-off-by: default avatarJames Bottomley <James.Bottomley@HansenPartnership.com>
    Cc: stable@vger.kernel.org
    Reviewed-by: default avatarJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
    Tested-by: default avatarJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
    Signed-off-by: default avatarJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
    e2fb992d