From mboxrd@z Thu Jan  1 00:00:00 1970
From: Keir Fraser <keir.xen@gmail.com>
Subject: Re: [PATCH 2/2] x86/microcode: enable boot time
 (pre-Dom0) loading
Date: Thu, 01 Dec 2011 05:25:40 +0000
Message-ID: <CAFCC054.262CD%keir.xen@gmail.com>
References: <4ED7423602000078000648FE@nat28.tlf.novell.com>
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To: Jan Beulich <JBeulich@suse.com>
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On 01/12/2011 08:00, "Jan Beulich" <JBeulich@suse.com> wrote:

>>>> On 30.11.11 at 10:05, Keir Fraser <keir.xen@gmail.com> wrote:
>> On 30/11/2011 16:27, "Jan Beulich" <JBeulich@suse.com> wrote:
>> 
>>> 
>>> In order to not convert the spin_lock() in microcode_update_cpu() (and
>>> then obviously also all other uses on microcode_mutex) to
>>> spin_lock_irqsave() (which would be undesirable for the hypercall
>>> context in which the function also runs), the boot time handling gets
>>> done using a tasklet (instead of using on_selected_cpus()).
>> 
>> Can you explain this some more? Why would the conversion to
>> spin_lock_irqsave be required when spin_lock is sufficient for current usage
>> from dom0 hypercall?
> 
> Because check_lock() wants locks to be acquired consistently?

Oh I see, and we use continue_hypercall_on_cpu() in the hypercall case.
Makes sense then.

 -- Keir

> Jan
>