linux-kernel - Re: [patch 0/4] x86: AMD microcode patch loading v2 fixes

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Date:	Wed, 30 Jul 2008 12:34:04 +0200
From:	"Dmitry Adamushko" <dmitry.adamushko@...il.com>
To:	"Peter Oruba" <peter.oruba@....com>
Cc:	"Max Krasnyansky" <maxk@...lcomm.com>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Tigran Aivazian" <tigran@...azian.fsnet.co.uk>,
	"H. Peter Anvin" <hpa@...or.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [patch 0/4] x86: AMD microcode patch loading v2 fixes

2008/7/30 Dmitry Adamushko <dmitry.adamushko@...il.com>:
> 2008/7/30 Peter Oruba <peter.oruba@....com>:
>>> [ ... ]
>>
>> Since ucode updates may fix severe issues, it is supposed to happen as early
>> as possible. If you re-plug your CPU into your socket, your BIOS also
>> applies a ucode patch, but that won't necessarily be the latest and critical
>> one.
>
> Hum, let's say we don't do it from cpu-hotplug handlers [1] but from
> start_secondary() before calling cpu_idle()? [*]
>
> This way, we do it before any other task may have a chance to run on a
> cpu which is not a case with cpu-hotplug handlers
> (and we don't mess-up with cpu-hotplug events :-)
>
> [ the drawback is that 'microcode' subsystem is not local to
> microcode.c anymore ]
>
> [1] if we need a sync. operation in cpu-hotplug handlers and IPI is
> not ok (say, we need to run in a sleepablel context) then perhaps it's
> workqueues + wait_on_cpu_work(). But then it's not a bit later than
> could have been with [*].
>
> heh, this issue has already popped up in another thread so it should
> be fixed asap, imho.
>
> Ingo, Peter? What would be the best way from your pov?

or let's just use smth like a patch below so far:

(non-white-space-damaged version is enclosed)

--- kernel/cpu.c-old    2008-07-30 12:31:15.000000000 +0200
+++ kernel/cpu.c        2008-07-30 12:32:02.000000000 +0200
@@ -349,6 +349,8 @@ static int __cpuinit _cpu_up(unsigned in
                goto out_notify;
        BUG_ON(!cpu_online(cpu));

+       cpu_set(cpu, cpu_active_map);
+
        /* Now call notifier in preparation. */
        raw_notifier_call_chain(&cpu_chain, CPU_ONLINE | mod, hcpu);

@@ -383,9 +385,6 @@ int __cpuinit cpu_up(unsigned int cpu)

        err = _cpu_up(cpu, 0);

-       if (cpu_online(cpu))
-               cpu_set(cpu, cpu_active_map);
-
 out:
        cpu_maps_update_done();
        return err;


>
>
>>
>> Peter
>>
>
> --
> Best regards,
> Dmitry Adamushko
>



-- 
Best regards,
Dmitry Adamushko

View attachment "move-cpu_set-cpu_active_map.patch" of type "text/x-patch" (554 bytes)