Messages in this thread | | | Date | Sat, 17 Aug 2013 09:42:56 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86, apic: Enable x2APIC physical when cpu < 256 native |
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* Youquan Song <youquan.song@linux.intel.com> wrote:
> > No problem - you might want to send another patch adding some comments to > > the code, explaining why we don't switch to physical mode, quoting from > > the SDM and so. > > Here is the revert patch. > > Subject: [PATCH] Revert "x86/apic: Enable x2APIC physical mode on native hardware too, when there are fewer than 256 CPUs" > > x2APIC without interrupt remapping is not architecture and no guarantee it > will work in future. > There are some words in SDM3, 10.12.7 Initialization by System > Software Routing of device interrupts to local APIC units operating in > x2APIC mode requires use of the interrupt-remapping architecture > specified in the Intel Virtualization Technology for Directed I/O, > Revision 1.3. Because of this, BIOS must enumerate support for and > software must enable this interrupt remapping with Extended Interrupt > Mode Enabled before it enabling x2APIC mode in the local APIC units. > > This reverts commit 3d1acb49d22fbbae96524040e9e2d4cbbb3adbef, do not use > x2apic_pysical mode if interrupt remapping is not enabled even at CPU > number fewer than 256. > > Signed-off-by: Youquan Song <youquan.song@intel.com> > --- > arch/x86/kernel/apic/apic.c | 7 +++++-- > 1 files changed, 5 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c > index d9dd5a6..eca89c5 100644 > --- a/arch/x86/kernel/apic/apic.c > +++ b/arch/x86/kernel/apic/apic.c > @@ -1622,8 +1622,11 @@ void __init enable_IR_x2apic(void) > goto skip_x2apic; > > if (ret < 0) { > - /* IR is required if there is APIC ID > 255 */ > - if (max_physical_apicid > 255) { > + /* IR is required if there is APIC ID > 255 even when running > + * under KVM > + */ > + if (max_physical_apicid > 255 || > + !hypervisor_x2apic_available()) {
Firstly, please use the customary (multi-line) comment style:
/* * Comment ..... * ...... goes here. */
specified in Documentation/CodingStyle.
Secondly, please send a patch against a vanilla (e.g. v3.11-rc5) kernel, as I've already zapped your previous patch from tip:x86/apic per your request.
Thanks,
Ingo
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