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From:   Andi Kleen <andi@firstfloor.org>
To:     Dan Williams <dan.j.williams@intel.com>
Cc:     Bjorn Helgaas <bhelgaas@google.com>, Nadav Amit <namit@vmware.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>, Borislav Petkov <bp@suse.de>,
        Toshi Kani <toshi.kani@hpe.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Ingo Molnar <mingo@kernel.org>,
        "Kleen\, Andi" <andi.kleen@intel.com>
Subject: Re: [PATCH 3/3] resource: Introduce resource cache
References: <20190613045903.4922-1-namit@vmware.com>
        <20190613045903.4922-4-namit@vmware.com>
        <20190617215750.8e46ae846c09cd5c1f22fdf9@linux-foundation.org>
        <98464609-8F5A-47B9-A64E-2F67809737AD@vmware.com>
        <8072D878-BBF2-47E4-B4C9-190F379F6221@vmware.com>
        <CAErSpo5eiweMk2rfT81Kwnpd=MZsOa01prPo_rAFp-MZ9F2xdQ@mail.gmail.com>
        <CAPcyv4iAbWnWUT2d2VhnvuHvJE0-Vxgbf1TYtOPjkR6j3qROtw@mail.gmail.com>
Date:   Thu, 20 Jun 2019 14:31:48 -0700
In-Reply-To: <CAPcyv4iAbWnWUT2d2VhnvuHvJE0-Vxgbf1TYtOPjkR6j3qROtw@mail.gmail.com>
        (Dan Williams's message of "Wed, 19 Jun 2019 14:53:54 -0700")
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Dan Williams <dan.j.williams@intel.com> writes:
>
> The underlying issue is that the x86-PAT implementation wants to
> ensure that conflicting mappings are not set up for the same physical
> address. This is mentioned in the developer manuals as problematic on
> some cpus. Andi, is lookup_memtype() and track_pfn_insert() still
> relevant?

There have been discussions about it in the past, and the right answer
will likely differ for different CPUs: But so far the official answer
for Intel CPUs is that these caching conflicts should be avoided.

So I guess the cache in the original email makes sense for now.

-Andi