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

["Michael S. Tsirkin" <mst@redhat.com>]

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 <lersek@redhat.com> 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" <mst@redhat.com> (supporter:ACPI/SMBIOS)
> >>> Cc: Igor Mammedov <imammedo@redhat.com> (supporter:ACPI/SMBIOS)
> >>> Cc: Paolo Bonzini <pbonzini@redhat.com> (maintainer:X86)
> >>> Cc: Richard Henderson <rth@twiddle.net> (maintainer:X86)
> >>> Cc: Eduardo Habkost <ehabkost@redhat.com> (maintainer:X86)
> >>> Cc: Ruiyu Ni <ruiyu.ni@intel.com>
> >>> Signed-off-by: Laszlo Ersek <lersek@redhat.com>
> >>> ---
> >>>  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 <imammedo@redhat.com>
> >>
> > 
> > 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?