Re: [Xen-devel] [PATCH RFC 19/20] acpi: Set HW_REDUCED_ACPI in FADT if IOAPIC is not supported

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.04.16 at 03:25, <boris.ostrovsky@xxxxxxxxxx> wrote:
> With this flags set guests will not try to set up SCI.

I've just read through the respective ACPI spec section again, and
I couldn't find a reference to SCI from there ("Hardware-Reduced
ACPI"). Can you clarify this connection please. Also there are other
consequences of setting that flag, so in order to understand the
reasons behind this change in case of future problems I think the
description here will need to be significantly extended, despite the
change being so small.

> --- a/xen/common/libacpi/build.c
> +++ b/xen/common/libacpi/build.c
> @@ -555,6 +555,8 @@ void acpi_build_tables(struct acpi_config *config, 
> unsigned long physical)
>      fadt->x_dsdt = config->mem_ops.v2p(dsdt);
>      fadt->firmware_ctrl   = config->mem_ops.v2p(facs);
>      fadt->x_firmware_ctrl = config->mem_ops.v2p(facs);
> +    if ( !(config->table_flags & ACPI_BUILD_IOAPIC) )
> +        fadt->flags |= (1<<20); /* HW_REDUCED_ACPI */

I think this would better be made a suitable #define in acpi2_0.h.

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel