Messages in this thread | | | Date | Sun, 6 Jul 2014 20:28:05 +0300 | From | Gleb Natapov <> | Subject | Re: [PATCH] x86: Make x2APIC support depend on interrupt remapping or guest support |
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On Sun, Jul 06, 2014 at 05:49:09PM +0200, Jan Kiszka wrote: > On 2014-07-06 17:41, Gleb Natapov wrote: > > On Sun, Jul 06, 2014 at 05:24:27PM +0200, Jan Kiszka wrote: > >> On 2014-07-06 17:12, Gleb Natapov wrote: > >>> On Sat, Jul 05, 2014 at 09:47:54AM +0200, Jan Kiszka wrote: > >>>> From: Jan Kiszka <jan.kiszka@siemens.com> > >>>> > >>>> We are able to use x2APIC mode in the absence of interrupt remapping on > >>>> certain hypervisors. So it if fine to disable IRQ_REMAP without having > >>>> to give up x2APIC support. > >>> FWIW I did similar thing back when I added x2apic to KVM: > >>> http://linux.derkeiler.com/Mailing-Lists/Kernel/2009-06/msg14579.html > >>> But was advised against it. > >> > >> I don't get the point from that thread. > > It is not architectural to use x2apic without irq remapping, so Suresh > > Slightly off-topic for this patch: Is this dependency documented > somewhere? I guess there are broken systems where it can fail, but none > of the (Intel) boxes I tried so far had problems with x2APIC mode on > (given APIC IDs < 255) and IRQ remapping disabled. Not sure I saw that written, but I was told many times that this is so.
-- Gleb.
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