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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> 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).

Jan


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