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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Tue, 7 Feb 2023 08:20:31 -0800
Message-ID: <CAHk-=wi53OX86-yLBp4rCHOH67XhVbzV78qa63mh4-rOhxQSLw@mail.gmail.com>
Subject: Re: [PATCH 4/6] x86/mtrr: don't let mtrr_type_lookup() return MTRR_TYPE_INVALID
To:     Juergen Gross <jgross@suse.com>
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org,
        lists@nerdbynature.de, mikelley@microsoft.com,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>
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On Mon, Feb 6, 2023 at 11:29 PM Juergen Gross <jgross@suse.com> wrote:
>
> mtrr_type_lookup() should always return a valid memory type. In case
> there is no information available, it should return the default UC.

Why isn't the second case (ie MTRR_STATE_MTRR_ENABLED not being set)
returning 'mtrr_state.def_type'. That's what the hw does, no?

> At the same time the mtrr_type_lookup() stub for the !CONFIG_MTRR
> case should set uniform to 1, as if the memory range would be
> covered by no MTRR at all.

.. but you didn't do that for the CONFIG_MTRR, so now they return
MTRR_TYPE_UNCACHABLE, but don't set uniform=1.

              Linus