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SubjectRe: Why Linux kernel forced to enter X2APIC mode( just because of booting cpu has supported x2apic) without depending on BIOS' setting in MSR->x2apic enablement bit ?
On 12/18/2012 09:49 AM, Yinghai Lu wrote:
>
> So you need to make cpuid show does not support x2apic --- check with
> intel they have way to do that.
>

No, but there is a flag in ACPI that "this BIOS is broken with x2APIC".
Setting that flag as opposed to fixing the bugs, though is very much not
recommended, however; the lack of interrupt routing means there are ways
for a rogue device to compromise the security provided by VT-d, see:

http://www.invisiblethingslab.com/resources/2011/Software%20Attacks%20on%20Intel%20VT-d.pdf

-hpa




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