linux-kernel - Re: [PATCH 2/2] intel_microcode, Fix long microcode load time when firmware file is missing

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Date:	Mon, 21 Oct 2013 20:20:50 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Prarit Bhargava <prarit@...hat.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	x86@...nel.org, herrmann.der.user@...glemail.com,
	tigran@...azian.fsnet.co.uk
Subject: Re: [PATCH 2/2] intel_microcode, Fix long microcode load time when
 firmware file is missing

On Mon, Oct 21, 2013 at 5:35 AM, Prarit Bhargava <prarit@...hat.com> wrote:
> If no firmware is found on the system that matches the processor, the
> microcode module can take hours to load.  For example on recent kernels
> when loading the microcode module on an Intel system:
>
> [  239.532116] microcode: CPU0 sig=0x306e4, pf=0x1, revision=0x413
> [  299.693447] microcode: CPU1 sig=0x306e4, pf=0x1, revision=0x413
> [  359.821972] microcode: CPU2 sig=0x306e4, pf=0x1, revision=0x413
> [  419.960263] microcode: CPU3 sig=0x306e4, pf=0x1, revision=0x413
> [  480.090024] microcode: CPU4 sig=0x306e4, pf=0x1, revision=0x413
> ...
> [ 2825.151364] microcode: CPU43 sig=0x306e4, pf=0x1, revision=0x413
> [ 2885.280863] microcode: CPU44 sig=0x306e4, pf=0x1, revision=0x413
> [ 2945.410719] microcode: CPU45 sig=0x306e4, pf=0x1, revision=0x413
> [ 3005.540541] microcode: CPU46 sig=0x306e4, pf=0x1, revision=0x413
> [ 3065.670405] microcode: CPU47 sig=0x306e4, pf=0x1, revision=0x413
> ...
> etc.
>
> Similarly there is a 60 second "hang" when loading the AMD module, which
> isn't as bad as the Intel situation, but it is a noticeable delay in the
> system boot and can be improved upon.
>
> Using request_firmware_nowait() seems more appropriate here and then we
> can avoid these delays, resulting in very quick load times for the
> microcode.

request_firmware_nowait() should be a good idea for the problem, but
why do you pass FW_ACTION_NOHOTPLUG as uevent?  It is used now
by drivers which requires their own user-space applications to handle
the request by polling the firmware device under sysfs.

So I am wondering if your microcode case belongs to the above case
of FW_ACTION_NOHOTPLUG?

And why don't you pass FW_ACTION_HOTPLUG? and you are sure
that udev isn't required to handle your microcode update request?


Thanks,
--
Ming Lei
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