linux-kernel - Re: [PATCH v2 2/8] x86/mtrr: support setting MTRR state for software defined MTRRs

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Date:   Tue, 14 Feb 2023 10:02:51 +0100
From:   Juergen Gross <jgross@...e.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        lists@...dbynature.de, mikelley@...rosoft.com,
        torvalds@...ux-foundation.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v2 2/8] x86/mtrr: support setting MTRR state for software
 defined MTRRs

On 14.02.23 09:58, Borislav Petkov wrote:
> On Tue, Feb 14, 2023 at 08:04:47AM +0100, Juergen Gross wrote:
>> Okay, if you really want to dictate the allowed use cases (this seems to be
> 
> Read upthread - TDX guests cause #VEs for MTRR accesses. #VEs which are
> unneeded and should be avoided if possible.

Of course, I don't question the need for TDX guests to use the overwrite.

> 
>> a layering violation), but you are the maintainer of that code.
> 
> And why are you so against catching misuses of this, which should
> absolutely *not* be needed by anything else

I just don't like the idea of trying to catch all possible misuses in
lower levels, at the same time introducing the need to modify those
tests in case a new valid use case is popping up.

But as said, you are the maintainer, so its your final decision.


Juergen

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