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    SubjectRe: [PATCH 1/2] VMware detection support for x86 and x86-64

    * Yan Li <elliot.li.tech@gmail.com> wrote:

    > On Mon, Sep 08, 2008 at 05:34:07PM -0700, H. Peter Anvin wrote:
    > >> VMware may change the PCI ID at their will so I prefer checking the
    > >> DMI since it's easier.
    > >>
    > >> So if we ditched the official method we run the risk of some false
    > >> negatives. But checking the DMI manufacturer would be good enough.
    > >>
    > >
    > > If we get false negatives that is quite frankly their problem, not ours.
    > > If nothing else, we should be able to look for a host bridge with the
    > > VMWare vendor ID -- that should arguably be safer than DMI.
    >
    > I found that in this situation we can't use PCI info. My intention to
    > do this is to fix the false warning from
    > arch/x86/kernel/cpu/mtrr/main.c (around L695). When booting a VMware
    > guest we got:
    > "WARNING: strange, CPU MTRRs all blank?"
    >
    > For VMware guest this warning is false, just as that for a KVM guest.
    >
    > This code is from mtrr_trim_uncached_memory(), and used by
    > setup_arch(), which is used far before PCI is ready.
    >
    > Therefore I think we can only use DMI here. Any idea?

    PCI quirks can be used almost arbitrarily early stage, see:
    arch/x86/kernel/early-quirks.c.

    Adding a VM identification callback to early-quirks.c would be fine. But
    if there's a reliable and specific enough DMI string that's fine as
    well. (but PCI is better, since it's a generally more stable enumeration
    interface)

    Ingo


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