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    SubjectRe: 2.6.26, PAT and AMD family 6
    On 07-05-08 21:39, Daniel Hazelton wrote:

    > HPA asked about why they used a whitelist instead of a blacklist in [1]. The
    > answer (in [2]) was that those are the CPU's that are guaranteed to properly
    > support PAT (no known or potential errata). However in [3] Dean Gaudet
    > complained about the AMD detection code having a limit that the Intel
    > detection code did not.

    And in that thread both HPA and Ingo Molnar -- two of the three x86 arch
    maintainers -- agreed that a whitelist is the wrong approach, with HPA
    commenting that it lead to vendor lockin. And here I am talkng to an
    Intel employee about why my entire AMD CPU family was excluded.

    So why is this thing now in mainline with Ingo's sign-off and not a line
    of changelog to explain it?

    > ^^^^^---- Here in Rene's patch...


    > Wouldn't this be better if written the same as the Intel side, ie:
    > if (c->x86 >= 0xF && (c->x86 == 6 && c->x86_model == 7))
    > (or even with c->x86_model >= 7 ?)

    I doubt it, given that that condition would optimize to 0 but assuming
    s/&&/||/ that's still excluding my previous Duron model 4 which, as far
    as I'm aware, had functional PAT as well. Nor am I myself aware of any
    model 1 trouble. Really, this whitelist seems a pretty bad idea.

    > [1]
    > [2]
    > [3]


    -- Why is this thing in with the whitelist over the objection of arch
    -- why is this thing in without a single line of changelog?
    -- Why does this thing hide the fact that my CPU does have PAT from
    me (even though it might elect to not trust it)?


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