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Re: [Qemu-devel] [PATCH] hw/i386: fill in the CENTURY field of the FADT
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH] hw/i386: fill in the CENTURY field of the FADT (FACP) ACPI table |
Date: |
Thu, 7 Jan 2016 11:07:46 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 |
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