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

[Paolo Bonzini]

On 07/01/2016 12:22, Michael S. Tsirkin wrote:
> On Thu, Jan 07, 2016 at 11:07:46AM +0100, Paolo Bonzini wrote:
>>
>>
>> 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
> 
> Yes - thanks!
> I picked this up - should I add your Reviewed-by tag?

Sure!

Reviewed-by: Paolo Bonzini <address@hidden>

Paolo