linux-kernel - Re: ibmvtpm byteswapping inconsistency

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Date:   Thu, 26 Jan 2017 15:05:36 -0700
From:   Jason Gunthorpe <jgunthorpe@...idianresearch.com>
To:     Michal Such??nek <msuchanek@...e.de>,
        Nayna Jain <nayna@...ux.vnet.ibm.com>
Cc:     Ashley Lai <ashleydlai@...il.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Peter Huewe <peterhuewe@....de>,
        Marcel Selhorst <tpmdd@...horst.net>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        tpmdd-devel@...ts.sourceforge.net, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: ibmvtpm byteswapping inconsistency

On Thu, Jan 26, 2017 at 09:22:48PM +0100, Michal Such??nek wrote:

> This is repeated a few times in the driver so I added memset to quiet
> gcc and make behavior deterministic in case the unused fields get some
> meaning in the future.

Yep, reserved certainly needs to be zeroed.. Can you send a patch?
memset is overkill...

> However, in tpm_ibmvtpm_send the structure is initialized as
> 
> 	struct ibmvtpm_crq crq;
>         __be64 *word = (__be64 *)&crq;
> ...
>         crq.valid = (u8)IBMVTPM_VALID_CMD;
>         crq.msg = (u8)VTPM_TPM_COMMAND;
>         crq.len = cpu_to_be16(count);
>         crq.data = cpu_to_be32(ibmvtpm->rtce_dma_handle);
> 
> and submitted with
> 
> 	rc = ibmvtpm_send_crq(ibmvtpm->vdev, be64_to_cpu(word[0]),
>                               be64_to_cpu(word[1]));
> meaning it is swapped twice.

No idea, Nayna may know.

My guess is that '__be64 *word' should be 'u64 *word'...

Jason