Re: [Xen-devel] [RFC PATCH V2 2/4] Tool/ACPI: DSDT extension to support more vcpus

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Mon, Sep 04, 2017 at 11:07:14AM +0800, Lan Tianyu wrote:
> On 2017年09月01日 17:41, Roger Pau Monné wrote:
> > On Fri, Sep 01, 2017 at 10:54:02AM +0800, Lan Tianyu wrote:
> >> On 2017年08月31日 23:38, Roger Pau Monné wrote:
> >>> On Thu, Aug 31, 2017 at 01:01:47AM -0400, Lan Tianyu wrote:
> >>>> This patch is to change DSDT table for processor object to support >128 
> >>>> vcpus
> >>>> accroding to ACPI spec 8.4 Declaring Processors
> >>>>
> >>>> Signed-off-by: Lan Tianyu <tianyu.lan@xxxxxxxxx>
> >>>> ---
> >>>>  tools/libacpi/mk_dsdt.c | 18 ++++++++++++------
> >>>>  1 file changed, 12 insertions(+), 6 deletions(-)
> >>>>
> >>>> diff --git a/tools/libacpi/mk_dsdt.c b/tools/libacpi/mk_dsdt.c
> >>>> index 2daf32c..6c4c325 100644
> >>>> --- a/tools/libacpi/mk_dsdt.c
> >>>> +++ b/tools/libacpi/mk_dsdt.c
> >>>> @@ -24,6 +24,8 @@
> >>>>  #include <xen/arch-arm.h>
> >>>>  #endif
> >>>>  
> >>>> +#define CPU_NAME_FMT      "P%.03X"
> >>>> +
> >>>>  static unsigned int indent_level;
> >>>>  static bool debug = false;
> >>>>  
> >>>> @@ -196,10 +198,14 @@ int main(int argc, char **argv)
> >>>>      /* Define processor objects and control methods. */
> >>>>      for ( cpu = 0; cpu < max_cpus; cpu++)
> >>>>      {
> >>>> -        push_block("Processor", "PR%02X, %d, 0x0000b010, 0x06", cpu, 
> >>>> cpu);
> >>>> +        unsigned int apic_id = cpu * 2;
> >>>
> >>> This is fragile, ideally there should be a single point where the APIC
> >>> ID is calculated. Although there are already two places where the APIC
> >>> ID is calculated, in hvmloader and libxl.
> >>>
> >>> And I'm not sure how to use any of those here in order to avoid
> >>> introducing a third one.
> >>
> >> The mk_dsdt is independent tool to build dsdt table. It wasn't linked
> >> with libxl and hvmloader. We can't reuse old function to do that.
> >>
> >> But I think we may introduce a new LAPIC_ID(vcpu) in the arch head
> >> file(i.e, #include <xen/arch-x86/xen.h>) and replace old ones.
> > 
> > There's already a LAPIC_ID macro in hvmloader headers which should be
> > placed somewhere suitable.
> 
> Yes, this is what I mentioned.

Jan has expressed some concerns with removing the hook, see:

<59A94E320200007800176754@xxxxxxxxxxxxxxxxxxxxxxx>

> > What about removing the lapic_id hook from
> > acpi_config and placing the LAPIC_ID macro in the libacpi.h header?
> 
> I think this should be ARCH specific. I am not sure whether ARM follows
> rule of "apic_id = vcpu_id *2".
> 
> Julien, could you give some inputs? Thanks.

AFAIK ARM doesn't have a local APIC, so there are no xAPIC/x2APIC
entries in the ARM MADT.

Roger.

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