linux-kernel - Re: [PATCH v1 2/2] firmware: dmi_scan: Pass dmi_entry

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Message-ID: <20200120224204.4e5cc0df@endymion>
Date:   Mon, 20 Jan 2020 22:42:04 +0100
From:   Jean Delvare <jdelvare@...e.de>
To:     ebiederm@...ssion.com (Eric W. Biederman)
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Dave Young <dyoung@...hat.com>, linux-efi@...r.kernel.org,
        ard.biesheuvel@...aro.org, matt@...eblueprint.co.uk,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: Re: [PATCH v1 2/2] firmware: dmi_scan: Pass dmi_entry_point to
 kexec'ed kernel

On Mon, 20 Jan 2020 10:04:04 -0600, Eric W. Biederman wrote:
> Second.  I looked at your test results and they don't directly make
> sense.  dmidecode bypasses the kernel completely or it did last time
> I looked so I don't know why you would be using that to test if
> something in the kernel is working.

That must have been long ago. A recent version of dmidecode (>= 3.0)
running on a recent kernel
(>= d7f96f97c4031fa4ffdb7801f9aae23e96170a6f, v4.2) will read the DMI
data from /sys/firmware/dmi/tables, so it is very much relying on the
kernel doing the right thing. If not, it will still try to fallback to
reading from /dev/mem directly on certain architectures. You can force
that old method with --no-sysfs.

Hope that helps,
-- 
Jean Delvare
SUSE L3 Support