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Tsirkin" , Paolo Bonzini , Igor Mammedov , Richard Henderson Subject: [Qemu-devel] [PATCH] hw/i386: fill in the CENTURY field of the FADT (FACP) ACPI table X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+patch=linaro.org@nongnu.org Sender: qemu-devel-bounces+patch=linaro.org@nongnu.org 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" (supporter:ACPI/SMBIOS) Cc: Igor Mammedov (supporter:ACPI/SMBIOS) Cc: Paolo Bonzini (maintainer:X86) Cc: Richard Henderson (maintainer:X86) Cc: Eduardo Habkost (maintainer:X86) Cc: Ruiyu Ni Signed-off-by: Laszlo Ersek --- hw/i386/acpi-build.c | 2 ++ 1 file changed, 2 insertions(+) -- 1.8.3.1 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; }