What's the status of x2APIC support in Linux kernel?

What's the status of x2APIC support in Linux kernel?

[Rijndael Cosque]

Hi all,

I found the x2APIC spec via http://www.intel.com/products/processor/manuals/.

Looks at present there is no x2APIC support in Linux kernel 2.6.24?

Is there any experimental patch available for Linux kernel? -- I
googled "x2APIC Linux";  looks no patch for now?

Thanks!

-- Rij

Re: What's the status of x2APIC support in Linux kernel?

[Jike Song]

On 2/1/08, Rijndael Cosque <rijcos@gmail.com> wrote:
> Hi all,
>
> I found the x2APIC spec via http://www.intel.com/products/processor/manuals/.
>
> Looks at present there is no x2APIC support in Linux kernel 2.6.24?
>
> Is there any experimental patch available for Linux kernel? -- I
> googled "x2APIC Linux";  looks no patch for now?
>
Maybe.   I have a question as well, what about the  status of I/O
xAPIC support in linux?  If it is not supported yet, is there any
effort to add it?  I'm interested in that, hopefully can take part in
the development.

Regards,

Re: What's the status of x2APIC support in Linux kernel?

[Peter Zijlstra]

On Fri, 2008-02-01 at 16:43 +0800, Rijndael Cosque wrote:
> Hi all,
> 
> I found the x2APIC spec via http://www.intel.com/products/processor/manuals/.
> 
> Looks at present there is no x2APIC support in Linux kernel 2.6.24?
> 
> Is there any experimental patch available for Linux kernel? -- I
> googled "x2APIC Linux";  looks no patch for now?

I think SGI has an implementation hidden away somewhere, Mike?

Re: What's the status of x2APIC support in Linux kernel?

[Andi Kleen]

"Jike Song" <albcamus@gmail.com> writes:

> On 2/1/08, Rijndael Cosque <rijcos@gmail.com> wrote:
>> Hi all,
>>
>> I found the x2APIC spec via http://www.intel.com/products/processor/manuals/.
>>
>> Looks at present there is no x2APIC support in Linux kernel 2.6.24?
>>
>> Is there any experimental patch available for Linux kernel? -- I
>> googled "x2APIC Linux";  looks no patch for now?

There are right no CPUs shipping which implement x2apic.

> Maybe.   I have a question as well, what about the  status of I/O
> xAPIC support in linux?  If it is not supported yet, is there any
> effort to add it?  I'm interested in that, hopefully can take part in
> the development.

xAPIC has been supported forever.

-Andi

Re: What's the status of x2APIC support in Linux kernel?

[Siddha, Suresh B]

On Fri, Feb 01, 2008 at 01:17:14PM +0100, Andi Kleen wrote:
> "Jike Song" <albcamus@gmail.com> writes:
> 
> > On 2/1/08, Rijndael Cosque <rijcos@gmail.com> wrote:
> >> Hi all,
> >>
> >> I found the x2APIC spec via http://www.intel.com/products/processor/manuals/.
> >>
> >> Looks at present there is no x2APIC support in Linux kernel 2.6.24?
> >>
> >> Is there any experimental patch available for Linux kernel? -- I
> >> googled "x2APIC Linux";  looks no patch for now?
> 
> There are right no CPUs shipping which implement x2apic.

That's correct. None of the released CPU's support it.

I am working on a patch enabling these future x2apic extensions and the plan 
is to post this kernel patch shortly.

thanks,
suresh

Re: What's the status of x2APIC support in Linux kernel?

[Jike Song]

On 2/1/08, Andi Kleen <andi@firstfloor.org> wrote:

> There are right no CPUs shipping which implement x2apic.
Thanks for your information.

> "Jike Song" <albcamus@gmail.com> writes:
> > Maybe.   I have a question as well, what about the  status of I/O
> > xAPIC support in linux?  If it is not supported yet, is there any
> > effort to add it?  I'm interested in that, hopefully can take part in
> > the development.
>
> xAPIC has been supported forever.

Thank you for your attention, Andi.

Oh, what do I mean is "I/O xAPIC", but not the "local xAPIC" or xAPIC
interrupt architecture introduced by Intel Pentium4 CPU.   It seems
that the "I/O xAPIC" hasn't been well documented yet, but some other
document do have some description about it.  Some Intel guys gave me
an URL for the document:

http://download.intel.com/technology/computing/vptech/Intel(r)_VT_for_Direct_IO.pdf

Section 5 and section 9.5 describe 'I/OxAPIC'. I'm not sure if it is
already supported by Linux, I guess it is not.

--
Best Regards,
Jike

Re: What's the status of x2APIC support in Linux kernel?

[Andi Kleen]

> Section 5 and section 9.5 describe 'I/OxAPIC'. I'm not sure if it is
> already supported by Linux, I guess it is not.

I'm not sure what the point of your questions is.  Do you want to 
do something concrete or are you just interested in random buzzwords?

Anyways as far as I know Linux supports the IO APICs implemented in all
x86 chipsets fully. That is it doesn't use every possible feature they have,
but I'm not aware of any particular limitation caused by Linux
not supporting some IO APIC feature.

The reason for the local x/APIC was that the original non x APIC did not support
more than 8 logical CPUs being active in the system. Presumably IO xAPIC 
refers to the IO APIC without this limitation too.

-Andi

Re: What's the status of x2APIC support in Linux kernel?

[Yinghai Lu]

On Feb 1, 2008 8:43 PM, Andi Kleen <andi@firstfloor.org> wrote:
> > Section 5 and section 9.5 describe 'I/OxAPIC'. I'm not sure if it is
> > already supported by Linux, I guess it is not.
>
> I'm not sure what the point of your questions is.  Do you want to
> do something concrete or are you just interested in random buzzwords?
>
> Anyways as far as I know Linux supports the IO APICs implemented in all
> x86 chipsets fully. That is it doesn't use every possible feature they have,
> but I'm not aware of any particular limitation caused by Linux
> not supporting some IO APIC feature.
>
> The reason for the local x/APIC was that the original non x APIC did not support
> more than 8 logical CPUs being active in the system. Presumably IO xAPIC
> refers to the IO APIC without this limitation too.

APIC: 4bit
xAPIC: 8bit?
x2APIC: 32bit? 4g logical cpu?

patch from SGI for 4096cpu/512node will use apicid as 16 bits, but
actually still use only from 8 bit.
they may wait from Intel release code for x2APIC support for extend
that to 16 bit.
x2APIC will use MSR instead of MMIO to access. that is good.
we don't need to go over mptable or ACPI madt to find phyaddress for local apic.

current code could work well with 8bit local APIC, and 4 bit IOAPIC.
I tried with lifting local apic id to 0x80 or 0x40 above, and io apic
for 0 in linuxbios then load kernel 2.6.21 ( one year ago). it worked
well

YH

Re: What's the status of x2APIC support in Linux kernel?

[Bjorn Helgaas]

On Friday 01 February 2008 11:08:23 am Siddha, Suresh B wrote:
> On Fri, Feb 01, 2008 at 01:17:14PM +0100, Andi Kleen wrote:
> > "Jike Song" <albcamus@gmail.com> writes:
> > 
> > > On 2/1/08, Rijndael Cosque <rijcos@gmail.com> wrote:
> > >> Hi all,
> > >>
> > >> I found the x2APIC spec via http://www.intel.com/products/processor/manuals/.
> > >>
> > >> Looks at present there is no x2APIC support in Linux kernel 2.6.24?
> > >>
> > >> Is there any experimental patch available for Linux kernel? -- I
> > >> googled "x2APIC Linux";  looks no patch for now?
> > 
> > There are right no CPUs shipping which implement x2apic.
> 
> That's correct. None of the released CPU's support it.
> 
> I am working on a patch enabling these future x2apic extensions and the plan 
> is to post this kernel patch shortly.

Are you adding x2apic support for both x86 and ia64, or only for x86?

Bjorn

Re: What's the status of x2APIC support in Linux kernel?

[Siddha, Suresh B]

On Thu, Feb 14, 2008 at 12:06:37PM -0700, Bjorn Helgaas wrote:
> 
> Are you adding x2apic support for both x86 and ia64, or only for x86?

x2apic extension is specific to x86. ia64 already has an advanced lsapic,
isn't it..

thanks,
suresh