Re: [PATCH] x86: Unbreak early processor microcode loading

From: Borislav Petkov
Date: Wed Apr 29 2015 - 14:44:06 EST

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

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[] = {
"/lib/firmware/updates/" UTS_RELEASE,
"/lib/firmware/" UTS_RELEASE,

and that's different from CONFIG_FIRMWARE_DIR.


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