Re: [Xen-devel] [PATCH 1/2] hvmloader: limit CPUs exposed to guests

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 06/16/2016 12:04 PM, Jan Beulich wrote:
>>>> On 16.06.16 at 17:37, <boris.ostrovsky@xxxxxxxxxx> wrote:
>> On 06/16/2016 11:25 AM, Jan Beulich wrote:
>>>>>> On 16.06.16 at 17:09, <boris.ostrovsky@xxxxxxxxxx> wrote:
>>>> On 06/16/2016 05:40 AM, Jan Beulich wrote:
>>>>
>>>> --- a/tools/firmware/hvmloader/acpi/mk_dsdt.c
>>>> +++ b/tools/firmware/hvmloader/acpi/mk_dsdt.c
>>>> @@ -150,6 +150,14 @@ int main(int argc, char **argv)
>>>>      indent(); printf("MSU, 8\n");
>>>>      pop_block();
>>>>  
>>>> +    /* Processor object helpers. */
>>>> +    push_block("Method", "PMAT, 2");
>>>> +    push_block("If", "LLess(Arg0, NCPU)");
>>>> +    stmt("Return", "ToBuffer(Arg1)");
>>>> +    pop_block();
>>>> +    stmt("Return", "Buffer() {0, 8, 0xff, 0xff, 0, 0, 0, 0}");
>>>>
>>>>
>>>> Could you explain what this is? (I suspect  this is related to MAT
>>>> object and I don't think I understand what it is).
>>> This is a helper routine for _MAT(), helping greatly to reduce
>>> overall size of the DSDT. It checks whether the CPU is within the
>>> range of available ones (online or offline), and if it isn't returns a
>>> static buffer instead of data read from MADT (as it's the purpose
>>> of this patch to remove these MADT entries for not present CPUs).
>> I meant just the last line (I understand what the routine is --- I am
>> not clear where MAT format is defined).
> That's a MADT entry of type ACPI_MADT_TYPE_LOCAL_APIC. Basically
> an equivalent of the ToBuffer(MAT) used previously (and now still used
> for CPU0).

Ah, ok -- makes sense now.

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>


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