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.

> 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.



> 
> I'm not sure why lapic_id needs to be a hook in any case, both it's
> callers use the same exact formula (cpu_id * 2).
> 
> Thanks, Roger.
> 


-- 
Best regards
Tianyu Lan

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