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

[Laszlo Ersek]

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?

Thanks
Laszlo