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

[Lan Tianyu <tianyu.lan@xxxxxxxxx>]

On 2017年09月04日 17:05, Roger Pau Monné wrote:
> 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>

So we still need to introduce LAPIC_ID() here, right?

> 
>>> 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.
> 




-- 
Best regards
Tianyu Lan

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