Messages in this thread |  | | | Date | Thu, 26 May 2011 00:01:19 +0200 (CEST) | | From | Thomas Gleixner <> | | Subject | Re: [PATCH v4] x86, vt-d: enable x2apic opt out |
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On Wed, 25 May 2011, Ingo Molnar wrote:
> > * Youquan Song <youquan.song@intel.com> wrote: > > > New version of VT-d2 specification > > (http://download.intel.com/technology > > /computing/vptech/Intel(r)_VT_for_Direct_IO.pdf) includes a new > > feature that provide firmware a way to request system software to > > opt out of enable x2APIC mode. DMAR ACPI table newly define flags.1 > > bit: x2APIC_OPT_OUT which is set to request System software opt out > > xAPIC mode if flags.0 bit:INTR_REMAP is also set. > > So why isnt the x2apic disabled in the CPUID? That's the canonical > way to unsupport a particular non-working CPU hw feature.
Because some committee decided to make it an ACPI feature. That's broken by design, but you can't change the stupid spec retroactively.
Thanks,
tglx
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