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

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

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. What about removing the lapic_id hook from
acpi_config and placing the LAPIC_ID macro in the libacpi.h header?

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.

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