linux-kernel - Re: [PATCH] x86/mtrr: Check if fixed MTRRs exist before saving them

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Message-ID: <ZZ4b6aq6s_GbpbcN@tassilo>
Date: Tue, 9 Jan 2024 20:24:09 -0800
From: Andi Kleen <ak@...ux.intel.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/mtrr: Check if fixed MTRRs exist before saving them

On Tue, Jan 09, 2024 at 08:06:26PM +0100, Thomas Gleixner wrote:
> On Fri, Jan 05 2024 at 08:37, Andi Kleen wrote:
> > This one place forgot to check the fixed capability.
> 
> What's the consequence of that missing chec

You get a WARN_ON for a WRMSR failing if you don't have the MSR.

> and shouldn't this have a Fixes tag?

It's more an ancient bug back dating back to my tenure in 2007, but here it is:

Fixes: 2b1f6278d77c ("[PATCH] x86: Save the MTRRs of the BSP before")

-Andi