linux-kernel - Re: [PATCH v9 0/5] tpm: Command duration logging and chip-specific override

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Date:	Wed, 13 Jul 2016 13:00:28 -0700
From:	Ed Swierk <eswierk@...portsystems.com>
To:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Cc:	tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
	Stefan Berger <stefanb@...ibm.com>
Subject: Re: [PATCH v9 0/5] tpm: Command duration logging and chip-specific override

On Wed, Jul 13, 2016 at 10:36 AM, Jason Gunthorpe
<jgunthorpe@...idianresearch.com> wrote:
> I think your bios is broken?

The BIOS is broken in many ways. I already have to pass
memmap=256M$0x80000000, otherwise PCIe extended config space
(MMCONFIG) is inaccessible. Also I found memmap=0x7000$0x7a7d0000
works around "APEI: Can not request [mem 0x7a7d0018-0x7a7d0067] for
APEI ERST registers", as the BIOS seems to be mistakenly reserving
0x7b7d0000-7b7d7000 instead.

> A working BIOS will look like this:
>
>  $ cat /proc/iomem  | grep -i fed400
>  fed40000-fed44fff : pnp 00:00
>
> It sets aside the struct resource during pnp:
>
>  [    0.097318] pnp: PnP ACPI init
>  [    0.097366] system 00:00: [mem 0xfed40000-0xfed44fff] has been reserved
>
> What did your system do?
>
> You should see prints like this:
>
>                 printk(KERN_DEBUG
>                        "e820: reserve RAM buffer [mem %#010llx-%#010llx]\n",
>                        start, end);
>
> Which only happen if E820_RAM is set, which is certainly not right for
> TPM memory.

On my system I see

e820: reserve RAM buffer [mem 0x0009b000-0x0009ffff]
e820: reserve RAM buffer [mem 0x75b02000-0x77ffffff]
e820: reserve RAM buffer [mem 0x7a1f6000-0x7bffffff]
e820: reserve RAM buffer [mem 0x7b800000-0x7bffffff]
e820: reserve RAM buffer [mem 0xfed30000-0xffffffff]
e820: reserve RAM buffer [mem 0x505deb000-0x507ffffff]

which doesn't make a whole lot of sense, as several of those areas
overlap each other, never mind devices.

> I don't know what kernel convention is to handle these sorts of
> defects?
>
> Is the use of the memmap kernel command line an appropriate work
> around?

It works for me, though I would like to know if there's another approach.

--Ed