linux-kernel - Re: Getting weird TPM error after rebasing my tree to security/next-general

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Message-ID: <20190204115823.GC26799@linux.intel.com>
Date:   Mon, 4 Feb 2019 13:58:23 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Tomas Winkler <tomas.winkler@...el.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>
Subject: Re: Getting weird TPM error after rebasing my tree to
 security/next-general

On Fri, Feb 01, 2019 at 10:04:35AM -0800, Linus Torvalds wrote:
> On Thu, Jan 31, 2019 at 12:45 PM Jarkko Sakkinen
> <jarkko.sakkinen@...ux.intel.com> wrote:
> >
> > I understand what you mean. Just surprised that this hasn't failed
> > before to anyone (the same driver has been even successfully used
> > on ARM64 with TrustZone based fTPM implementation). It has been in
> > for three years now.
> 
> Just to finish this thread off: it turns out that both ARM and ARM64
> worked fine, because neither did a memcpy(), but had explicit IO copy
> routines.
> 
> And in those explicit routines, 32-bit ARM did only byte accesses, and
> 64-bit ARM did 8-byte accesses for the bulk transfer part, but byte
> accesses for the unaligned head and tail of the IO area.
> 
> So I think it's all good. x86 used to work by luck (either because all
> machines that used that TPM chip always had ERMS, or because the
> people who didn't have it never cared), and ARM just worked because it
> would never do unaligned IO accesses anyway (well, I guess you can
> force them with "readl()" on an unaligned address, but then you just
> have yourself to blame).
> 
>            Linus

OK, thanks for the summary. This kind of answered to my question. Should
be sufficient to include the tpm_crb fix to the 5.1 PR.

/Jarkko