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    SubjectRe: [PATCH] ACPI, APEI, Add APEI _OSC support
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    On Thursday, June 16, 2011, Matthew Garrett wrote:
    > On Thu, Jun 16, 2011 at 08:40:11AM +0800, Huang Ying wrote:
    > > On 06/15/2011 08:17 PM, Matthew Garrett wrote:
    > > >> You means the "APEI Support" bit for standard UUID? Do you know which
    > > >> machine uses this bit? I can write the code, but I have no machine to
    > > >> test it.
    > > >
    > > > I have access to a Dell system that uses this.
    > >
    > > Great! Can you help us to test the code?
    >
    > Yup, no problem.
    >
    > > > Urgh. One machine I've looked at enables APEI if the WHEA _OSC call is
    > > > made, and then clears a flag if any other _OSC call is made. In that
    > > > specific case it doesn't seem to matter (the flag never actually gets
    > > > checked in any of the other codepaths), but it seems that the intention
    > > > is for the generic call to be made and the WHEA one to be made after
    > > > that.
    > >
    > > Yes. The WHEA call should be made after the generic one. Another
    > > situation is as follow:
    > >
    > > - Generic _OSC call without "APEI Support" bit is called (in
    > > acpi_bus_osc_support).
    > >
    > > - After some time, when we think it is good to turn on firmware first
    > > mode fully, usually after we checking HEST and initializing
    > > corresponding module, we make generic _OSC call with "APEI Support" bit
    > > to turn on firmware first mode fully in standard way.
    > >
    > > Is it a good idea to make generic _OSC call twice, one without "APEI
    > > Support" bit, the other with "APEI Support" bit?
    >
    > I think we probably need to make the HEST decision early, and use that
    > to decide how to make the generic call. Our experience has been that
    > many firmware vendors only expect _OSC to be called once with any given
    > UUID - multiple calls can result in unexpected behaviour.

    Not really, as long as the "query enable" bit is set.

    Thanks,
    Rafael


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