Re: Why Linux kernel forced to enter X2APIC mode( just because ofbooting cpu has supported x2apic) without depending on BIOS' setting in MSR->x2apicenablement bit ?

[H. Peter Anvin]

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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