於 二，2014-01-07 於 08:35 -0800，H. Peter Anvin 提到：
> On 01/07/2014 02:40 AM, joeyli wrote:
> >
> > Due to accessing CMOS through ASL need enable SMM support in OVMF,
>
> Why? The CMOS is its own ASL address space, and you need that anyway to
> be able to access the RTC proper. If you don't want to use it because
> you don't want to export any indication of a legacy RTC you should be
> able to just do I/O port references directly in your ASL.
>
> -hpa
>
>
ACPICA denied AML access RTC ports.
I tried to access 0x70, 0x71 ports in ASL on a real machine, ACPICA
denied AML access to those ports. I got the following dmesg:
hwvalid-0188 hw_validate_io_request: Denied AML access to port
0x0000000000000071/1
The code in acpica denied it:
linux/drivers/acpi/acpica/hwvalid.c
* This provides ACPICA with the desired port protections and
* Microsoft compatibility.
*
* Description of port entries:
[...]
* RTC: Real-time clock
* CMOS: Extended CMOS
[...]
*/
static const struct acpi_port_info acpi_protected_ports[] = {
[...]
{"RTC", 0x0070, 0x0071, ACPI_OSI_WIN_XP},
{"CMOS", 0x0074, 0x0076, ACPI_OSI_WIN_XP},
Document of Windows XP:
http://www.freelists.org/post/windows_errors/what-error-messages-really-mean-WinXP-IO-Ports-Blocked-from-Bios-AML-on-Windows-XP
If just for ACPI TAD testing, we can remove the port protection check of
RTC ports in hwvalid.c. I have read 0x70/0x71 port success after removed
the checking in acpica/hwvalid.c.
I will try to write RTC port in AML after remove acpica check, maybe
have other unpredictable situation.
Thanks a lot!
Joey Lee
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