On Tue, Mar 03, 2026 at 10:25:14AM +0100, Igor Mammedov wrote:
> Date: Tue, 3 Mar 2026 10:25:14 +0100
> From: Igor Mammedov <[email protected]>
> Subject: [PATCH v2 03/21] x86: q35: generate WDAT ACPI table
>
> It will generate WDAT table [1] customized for TCO watchdog.
> This allows Windows guests (Windows Server 2008/Vista+) to
> use TCO watchdog using built-in generic driver, which
> alleviates need to install vendor specific drivers.
>
> Given that enabling it might change guest behaviour
> (both Windows/Linux) the feature is disabled by default.
>
> Users that need it can enable the feature with
> following CLI option.
> -machine wdat=on
>
> 1)
> "Hardware Watchdog Timers Design Specification"
> https://uefi.org/acpi 'Watchdog Action Table (WDAT)'
>
> Signed-off-by: Igor Mammedov <[email protected]>
> Reviewed-by: Ani Sinha <[email protected]>
> ---
> include/hw/acpi/wdat-ich9.h | 15 +++++++
> hw/acpi/meson.build | 3 +-
> hw/acpi/wdat-ich9-stub.c | 15 +++++++
> hw/acpi/wdat-ich9.c | 90 +++++++++++++++++++++++++++++++++++++
> hw/i386/acpi-build.c | 12 +++++
> 5 files changed, 134 insertions(+), 1 deletion(-)
> create mode 100644 include/hw/acpi/wdat-ich9.h
> create mode 100644 hw/acpi/wdat-ich9-stub.c
> create mode 100644 hw/acpi/wdat-ich9.c
...
> +void build_ich9_wdat(GArray *table_data, BIOSLinker *linker, const char
> *oem_id,
> + const char *oem_table_id, uint64_t tco_base)
> +{
> + AcpiTable table = { .sig = "WDAT", .rev = 1, .oem_id = oem_id,
> + .oem_table_id = oem_table_id };
> + struct AcpiGenericAddress tco_rld = TCO_REG(tco_base, 0x0, 16);
> + struct AcpiGenericAddress tco2_sts = TCO_REG(tco_base, 0x6, 16);
> + struct AcpiGenericAddress tco1_cnt = TCO_REG(tco_base, 0x8, 16);
> + struct AcpiGenericAddress tco_tmr = TCO_REG(tco_base, 0x12, 16);
> +
> + acpi_table_begin(&table, table_data);
> + build_append_int_noprefix(table_data, 0x20, 4); /* Watchdog Header
> Length */
> + build_append_int_noprefix(table_data, 0xff, 2); /* PCI Segment */
> + build_append_int_noprefix(table_data, 0xff, 1); /* PCI Bus Number */
> + build_append_int_noprefix(table_data, 0xff, 1); /* PCI Device Number */
> + build_append_int_noprefix(table_data, 0xff, 1); /* PCI Function Number */
> + build_append_int_noprefix(table_data, 0, 3); /* Reserved */
> + /*
> + * limits/resolution are defined by ICH9 TCO spec
> + */
> + build_append_int_noprefix(table_data, 0x258, 4);/* Timer Period, ms */
> + build_append_int_noprefix(table_data, 0x3ff, 4);/* Maximum Count */
> + build_append_int_noprefix(table_data, 0x4, 4); /* Minimum Count */
Spec said: The time-out period before the WDT fires is recommended to be at
least 5 minutes and is required to be less than 4,294,967,296 count
intervals.
Here we encode 0x4 * 0x258 = 2400ms, less than 5 minutes. But I
understand because "5 minutes" is just "recommanded" by spec, so 2400ms is
okay.
LGTM,
Reviewed-by: Zhao Liu <[email protected]>
