Re: [Qemu-devel] [PATCH] hw/i386: fill in the CENTURY field of the FADT (FACP) ACPI table

[Paolo Bonzini]

On 04/01/2016 18:19, Laszlo Ersek wrote:
> On 12/10/15 19:53, Igor Mammedov wrote:
>> On Thu, 10 Dec 2015 18:25:34 +0100
>> Laszlo Ersek <address@hidden> wrote:
>>
>>> The ACPI specification (minimally versions 1.0b through 6.0) define
>>> the FADT.CENTURY field as:
>>>
>>>   The RTC CMOS RAM index to the century of data value (hundred and
>>>   thousand year decimals). If this field contains a zero, then the RTC
>>>   centenary feature is not supported. If this field has a non-zero
>>> value, then this field contains an index into RTC RAM space that OSPM
>>> can use to program the centenary field.
>>>
>>> The x86 targets generate ACPI payload, emulate an RTC
>>> (CONFIG_MC146818RTC), and that RTC supports the "centenary
>>> feature" (see occurrences of RTC_CENTURY in cmos_ioport_write() and
>>> cmos_ioport_read() in "hw/timer/mc146818rtc.c".)
>>>
>>> However, FADT.CENTURY is left at zero currently:
>>>
>>>   [06Ch 0108   1]            RTC Century Index : 00
>>>
>>> which -- according to analysis done by Ruiyu Ni at Intel -- should
>>> cause Linux and Windows 8+ to think the RTC centenary feature is
>>> unavailable, and cause Windows 7 to (incorrectly) assume that the
>>> offset to use is constant 0x32. (0x32 happens to be the right value
>>> on QEMU, but Windows 7 is wrong to assume anything at all).
>>>
>>> Exposing the right nonzero offset in FADT.CENTURY informs Linux and
>>> Windows 8+ about the right capabilities of the hardware, plus it
>>> retrofits our FADT to Windows 7's behavior.
>>>
>>> Regression tested with the following guests (all UEFI installs):
>>> - i386 Q35: Fedora 21 ("Fedlet" edition)
>>> - x86_64:
>>>   - i440fx:
>>>     - Fedora 21
>>>     - RHEL 6 and 7
>>>     - Windows 7 and 10
>>>     - Windows Server 2008 R2 and 2012 R2
>>>   - Q35:
>>>     - Fedora 22
>>>     - Windows 8.1
>>>
>>> Cc: "Michael S. Tsirkin" <address@hidden> (supporter:ACPI/SMBIOS)
>>> Cc: Igor Mammedov <address@hidden> (supporter:ACPI/SMBIOS)
>>> Cc: Paolo Bonzini <address@hidden> (maintainer:X86)
>>> Cc: Richard Henderson <address@hidden> (maintainer:X86)
>>> Cc: Eduardo Habkost <address@hidden> (maintainer:X86)
>>> Cc: Ruiyu Ni <address@hidden>
>>> Signed-off-by: Laszlo Ersek <address@hidden>
>>> ---
>>>  hw/i386/acpi-build.c | 2 ++
>>>  1 file changed, 2 insertions(+)
>>>
>>> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
>>> index 95e0c65..c5e6c4b 100644
>>> --- a/hw/i386/acpi-build.c
>>> +++ b/hw/i386/acpi-build.c
>>> @@ -42,6 +42,7 @@
>>>  #include "sysemu/tpm.h"
>>>  #include "hw/acpi/tpm.h"
>>>  #include "sysemu/tpm_backend.h"
>>> +#include "hw/timer/mc146818rtc_regs.h"
>>>  
>>>  /* Supported chipsets: */
>>>  #include "hw/acpi/piix4.h"
>>> @@ -334,6 +335,7 @@ static void fadt_setup(AcpiFadtDescriptorRev1
>>> *fadt, AcpiPmInfo *pm) if (max_cpus > 8) {
>>>          fadt->flags |= cpu_to_le32(1 <<
>>> ACPI_FADT_F_FORCE_APIC_CLUSTER_MODEL); }
>>> +    fadt->century = RTC_CENTURY;
>>>  }
>>>  
>>>  
>>
>> Reviewed-by: Igor Mammedov <address@hidden>
>>
> 
> Thanks.
> 
> Can someone please pick up this patch?

It should probably go in through Michael's tree, but I've queued it too
so that it isn't forgotten.

Paolo