Messages in this thread | | | Date | Thu, 20 Dec 2012 08:48:31 -0800 | From | "H. Peter Anvin" <> | Subject | Re: 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 ? |
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On 12/20/2012 08:46 AM, Yinghai Lu wrote: > On Thu, Dec 20, 2012 at 2:38 AM, Zhang, Lin-Bao (Linux Kernel R&D) > <linbao.zhang@hp.com> wrote: >> I think current core argument is our BIOS did following judgement , >> but Linux kernel did not(Linux seems just judge BSP supports x2apic mode or not by CPUID method) > > kernel checks that, if the BSP in x2apic mode, kernel will check if > intr-remapping can be enabled, otherwise > it will switch back to xapic mode. > >> Our BSP really supports x2apic mode, however,as this spec, our BIOS think some of configuration of server >> could not meet x2apic conditions ,So didn't place local xAPICs into x2apic mode. >> But linux kernel indeed enable x2apic mode(just believe BSP, didn't do above judgement) . so this is the conflict. > > so your BIOS is wrong, it does not enable intr-remapping. >
FWIW, I bought a *server* today and it didn't have interrupt remapping and x2APIC, I would consider it defective and return it.
-hpa
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