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    SubjectRe: i686 quirk for AMD Geode
    Date
    "H. Peter Anvin" <hpa@zytor.com> writes:
    > On 11/10/2009 09:24 AM, Alan Cox wrote:
    >>>
    >>> In the short term, yes, of course. However, if we're going to do
    >>> emulation, we might as well do it right.
    >>
    >> Why is using KVM doing it right ? It sounds like its doing it slowly,
    >> and hideously memory inefficiently. You are solving an uninteresting
    >> general case problem when you just need two tiny fixups (or perhaps 3 if
    >> you want to fix up early x86-64 prefetch)
    >
    > Why do we only need "two tiny fixups"? Where do we draw the line in
    > terms of ISA compatibility? One could easily argue that the Right
    > Thing[TM] is to be able to process any optional instruction -- otherwise
    > one has a very difficult place to draw a line.
    >
    > Consider SSE3, for example. Why should the same concept not apply to
    > SSE3 instructions as to CMOV?

    FWIW, the issue of the binary-only flashplayer.so came up later in the thread,
    but to add my few cents:

    When flash 10 was released the binary only 64-bit version generated
    instructions from the LAHF set unconditionally, in part because Windows chose
    to emulate those on the very few x86-64 platforms that didn't do them in
    hardware.

    At that time it would have been very nice from a "user support" point of view
    to be able to add LAHF emulation to support the software. Yes, it is ugly,
    binary-only code, but it is reasonably popular...

    Daniel

    ...in the end, in fact, popular enough to have at least a couple of people
    I know purchase a new CPU that did implement it, just for flash on Linux.
    --
    ✣ Daniel Pittman ✉ daniel@rimspace.net ☎ +61 401 155 707
    ♽ made with 100 percent post-consumer electrons
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