From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Cc: Peter Huewe <peterhuewe@gmx.de>,
Marcel Selhorst <tpmdd@selhorst.net>,
"moderated list:TPM DEVICE DRIVER"
<tpmdd-devel@lists.sourceforge.net>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH RFC 1/3] tpm_crb: expand struct crb_control_area to struct crb_regs
Date: Mon, 10 Oct 2016 07:45:08 +0300 [thread overview]
Message-ID: <20161010044508.GA5920@intel.com> (raw)
In-Reply-To: <20161009230737.GA23823@obsidianresearch.com>
On Sun, Oct 09, 2016 at 05:07:37PM -0600, Jason Gunthorpe wrote:
> On Sun, Oct 09, 2016 at 09:33:58PM +0300, Jarkko Sakkinen wrote:
>
> > > Sorry I missed this part.
> > >
> > > Here are the constraints for existing hardware:
> > >
> > > 1. All the existing CRB start only hardware has the iomem covering the
> > > control area and registers for multiple localities.
> > > 2. All the existing ACPI start hardware has only the control area.
> > >
> > > If you assume that SSDT does not have malicous behavior caused by either
> > > a BIOS bug or maybe a rootkit, then the current patch works for all the
> > > existing hardware.
> > >
> > > To counter-measure for unexpected behavior in non-existing hardware and
> > > buggy or malicious firmware it probably make sense to use crb_map_res to
> > > validate the part of the CRB registers that is not part of the control
> > > area.
>
> I don't know how much I'd assume BIOS authors do what you think - the
> spec I saw for this seems very vauge.
>
> Certainly checking that locality region falls within the acpi mapping
> seems essential.
>
> > > Doing it in the way you proposed does not work for ACPI start devices.
> > >
> > > For them it should be done in the same way as I'm doing in the existing
> > > patch as for ACPI start devices the address below the control area are
> > > never accessed. Having a separate crb_map_res for CRB start only devices
> > > is sane thing to do for validation.
> >
> > Alternative is to do two structures crb_regs_head and crb_regs_tail,
> > which might be cleaner. I'm fine with going either route.
>
> Since the iomem doesn't actually exist for a configuration having two
> pointers is the better choice. Make sure one is null for the
> configuration that does not support it.
>
> The negative offset thing is way too subtle.
Yeah, I do agree with you on this. Even if it was functionalliy correct,
it is hard to understand if you don't proactively work on the driver.
> Jason
/Jarkko
next prev parent reply other threads:[~2016-10-10 4:45 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-09 0:15 [PATCH RFC 0/3] Locality support for the CRB driver Jarkko Sakkinen
2016-10-09 0:15 ` [PATCH RFC 1/3] tpm_crb: expand struct crb_control_area to struct crb_regs Jarkko Sakkinen
2016-10-09 1:42 ` Jason Gunthorpe
2016-10-09 9:38 ` Jarkko Sakkinen
2016-10-09 16:49 ` Jason Gunthorpe
2016-10-09 18:06 ` Jarkko Sakkinen
2016-10-09 18:32 ` Jarkko Sakkinen
2016-10-09 18:33 ` Jarkko Sakkinen
2016-10-09 23:07 ` Jason Gunthorpe
2016-10-10 0:25 ` [tpmdd-devel] " Winkler, Tomas
2016-10-10 3:26 ` Jason Gunthorpe
2016-10-10 4:59 ` Jarkko Sakkinen
2016-10-10 4:45 ` Jarkko Sakkinen [this message]
2016-10-09 0:15 ` [PATCH RFC 2/3] tpm_crb: encapsulate crb_wait_for_reg_32 Jarkko Sakkinen
2016-10-09 0:15 ` [PATCH RFC 3/3] tpm_crb: request and relinquish locality 0 Jarkko Sakkinen
2016-10-09 6:35 ` [tpmdd-devel] " Winkler, Tomas
2016-10-09 9:25 ` Jarkko Sakkinen
2016-10-09 9:43 ` Winkler, Tomas
2016-10-09 10:47 ` Jarkko Sakkinen
2016-10-11 9:23 [PATCH 0/3] Locality support for the CRB driver Jarkko Sakkinen
2016-10-11 9:23 ` [PATCH RFC 1/3] tpm_crb: expand struct crb_control_area to struct crb_regs Jarkko Sakkinen
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