linux-kernel - Re: [PATCH] x86: Unbreak early processor microcode loading

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Message-ID: <20150429184338.GF5498@pd.tnic>
Date:	Wed, 29 Apr 2015 20:43:38 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
Cc:	Daniel J Blueman <daniel@...ascale.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Quentin Casasnovas <quentin.casasnovas@...cle.com>,
	Steffen Persvold <sp@...ascale.com>,
	linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH] x86: Unbreak early processor microcode loading

On Wed, Apr 29, 2015 at 03:23:57PM -0300, Henrique de Moraes Holschuh wrote:
> That would obviously work, but people often have other firmware
> built-in, so the likehood of CONFIG_EXTRA_FIRMWARE_DIR pointing to the
> root of a linux-firmware work tree or to "/lib/firmware" is not low at
> all.
> 
> In fact, it is natural to expect that CONFIG_EXTRA_FIRMWARE should point
> to something that will result in the same filenames as the kernel would
> want to use for regular firmware loading.  The current text of the
> Kconfig help for CONFIG_EXTRA_FIRMWARE even says so.

You mean that:

	  "These files should exist under
          the directory specified by the EXTRA_FIRMWARE_DIR option, which is
          by default the firmware subdirectory of the kernel source tree.

          For example, you might set CONFIG_EXTRA_FIRMWARE="usb8388.bin", copy
          the usb8388.bin file into the firmware directory, and build the kernel.
          Then any request_firmware("usb8388.bin") will be satisfied internally
          without needing to call out to userspace."

So people with lotsa firmware should put it all under one directory and
all should just work.

> So, FWIW, I do think we should always use the same path for builtin and
> regular firmware requests, based on the least-surprise principle.

We don't hardcode the path - only the name. What I gave was an example
only.

The regular microcode updates, i.e. the late ones, use firmware class
which has a bunch of hardcoded paths:

static const char * const fw_path[] = {
        fw_path_para,
        "/lib/firmware/updates/" UTS_RELEASE,
        "/lib/firmware/updates",
        "/lib/firmware/" UTS_RELEASE,
        "/lib/firmware"
};

and that's different from CONFIG_FIRMWARE_DIR.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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