linux-kernel - Re: [PATCH 4/7] x86/idle: Disable IBRS entering idle and enable it on wakeup

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Date:   Fri, 5 Jan 2018 00:45:58 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andrea Arcangeli <aarcange@...hat.com>
cc:     Tim Chen <tim.c.chen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Arjan Van De Ven <arjan.van.de.ven@...el.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/7] x86/idle: Disable IBRS entering idle and enable it
 on wakeup

On Fri, 5 Jan 2018, Andrea Arcangeli wrote:

> On Thu, Jan 04, 2018 at 03:22:09PM -0800, Tim Chen wrote:
> > No one should be calling this with IRQs enabled.  This check is probably
> > just paranoid.  I can get rid of it.
> 
> Yes, confirmed.
> 
> > It probably doesn't matter as we will be switching the check
> > to the spec_ctrl_ibrs a couple of patches later. 
> 
> The other problem with static_cpu_has is later the code intends to
> support the cpuid rescan post late microcode update which will set
> bits in boot_cpu_data (and transfer them to each cpu_has). If we'd
> only support early microcode update static_cpu_has should have been ok
> too.

What's the problem to make the early update mandatory for this?

Thanks,

	tglx