Add SBSA generic watchdog to virt machine type with
all necessary wiring for ACPI watchdog. Which includes
setting its frequency to 1KHz (max that WDAT is able to handle).

Signed-off-by: Igor Mammedov <[email protected]>
---
 include/hw/acpi/wdat-gwdt.h | 19 ++++++++
 include/hw/arm/virt.h       |  3 ++
 hw/acpi/meson.build         |  2 +
 hw/acpi/wdat-gwdt-stub.c    | 16 +++++++
 hw/acpi/wdat-gwdt.c         | 92 +++++++++++++++++++++++++++++++++++++
 hw/arm/Kconfig              |  1 +
 hw/arm/virt-acpi-build.c    | 16 +++++++
 hw/arm/virt.c               | 26 +++++++++++
 8 files changed, 175 insertions(+)
 create mode 100644 include/hw/acpi/wdat-gwdt.h
 create mode 100644 hw/acpi/wdat-gwdt-stub.c
 create mode 100644 hw/acpi/wdat-gwdt.c

diff --git a/include/hw/acpi/wdat-gwdt.h b/include/hw/acpi/wdat-gwdt.h
new file mode 100644
index 0000000000..42339e031e
--- /dev/null
+++ b/include/hw/acpi/wdat-gwdt.h
@@ -0,0 +1,19 @@
+/*
+ * GWDT Watchdog Action Table (WDAT) definition
+ *
+ * Copyright Red Hat, Inc. 2026
+ * Author(s): Igor Mammedov <[email protected]>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#ifndef QEMU_HW_ACPI_WDAT_GWDT_H
+#define QEMU_HW_ACPI_WDAT_GWDT_H
+
+#include "hw/acpi/aml-build.h"
+#include "hw/watchdog/sbsa_gwdt.h"
+
+void build_gwdt_wdat(GArray *table_data, BIOSLinker *linker, const char 
*oem_id,
+                     const char *oem_table_id, uint64_t rbase, uint64_t cbase,
+                     uint64_t freq);
+
+#endif /* QEMU_HW_ACPI_WDAT_GWDT_H */
diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
index 3b382bdf49..d47bb8a72d 100644
--- a/include/hw/arm/virt.h
+++ b/include/hw/arm/virt.h
@@ -82,6 +82,9 @@ enum {
     VIRT_NVDIMM_ACPI,
     VIRT_PVTIME,
     VIRT_ACPI_PCIHP,
+    VIRT_GWDT_WS0,
+    VIRT_GWDT_REFRESH,
+    VIRT_GWDT_CONTROL,
     VIRT_LOWMEMMAP_LAST,
 };
 
diff --git a/hw/acpi/meson.build b/hw/acpi/meson.build
index ba974b2f0f..200b525ae1 100644
--- a/hw/acpi/meson.build
+++ b/hw/acpi/meson.build
@@ -28,12 +28,14 @@ acpi_ss.add(when: 'CONFIG_ACPI_ICH9', if_true: 
files('ich9.c', 'ich9_tco.c', 'ic
 acpi_ss.add(when: 'CONFIG_ACPI_ERST', if_true: files('erst.c'))
 acpi_ss.add(when: 'CONFIG_IPMI', if_true: files('ipmi.c'), if_false: 
files('ipmi-stub.c'))
 acpi_ss.add(when: 'CONFIG_PC', if_false: files('acpi-x86-stub.c'))
+acpi_ss.add(when: 'CONFIG_WDT_SBSA', if_true: files('wdat-gwdt.c'))
 if have_tpm
   acpi_ss.add(files('tpm.c'))
 endif
 system_ss.add(when: 'CONFIG_ACPI', if_false: files('acpi-stub.c', 
'aml-build-stub.c', 'ghes-stub.c', 'acpi_interface.c'))
 system_ss.add(when: 'CONFIG_ACPI_PCI_BRIDGE', if_false: 
files('pci-bridge-stub.c'))
 system_ss.add(when: 'CONFIG_ACPI_ICH9', if_false: files('wdat-ich9-stub.c'))
+system_ss.add(when: 'CONFIG_WDT_SBSA', if_false: files('wdat-gwdt-stub.c'))
 system_ss.add_all(when: 'CONFIG_ACPI', if_true: acpi_ss)
 system_ss.add(when: 'CONFIG_GHES_CPER', if_true: files('ghes_cper.c'))
 system_ss.add(when: 'CONFIG_GHES_CPER', if_false: files('ghes_cper_stub.c'))
diff --git a/hw/acpi/wdat-gwdt-stub.c b/hw/acpi/wdat-gwdt-stub.c
new file mode 100644
index 0000000000..4d43783f70
--- /dev/null
+++ b/hw/acpi/wdat-gwdt-stub.c
@@ -0,0 +1,16 @@
+/*
+ * Copyright Red Hat, Inc. 2026
+ * Author(s): Igor Mammedov <[email protected]>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "hw/acpi/wdat-gwdt.h"
+
+void build_gwdt_wdat(GArray *table_data, BIOSLinker *linker, const char 
*oem_id,
+                     const char *oem_table_id, uint64_t rbase, uint64_t cbase,
+                     uint64_t freq)
+{
+    g_assert_not_reached();
+}
diff --git a/hw/acpi/wdat-gwdt.c b/hw/acpi/wdat-gwdt.c
new file mode 100644
index 0000000000..226ba3f01e
--- /dev/null
+++ b/hw/acpi/wdat-gwdt.c
@@ -0,0 +1,92 @@
+/*
+ * SBSA GWDT Watchdog Action Table (WDAT)
+ *
+ * Copyright Red Hat, Inc. 2026
+ * Author(s): Igor Mammedov <[email protected]>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "hw/acpi/aml-build.h"
+#include "hw/acpi/wdat-gwdt.h"
+#include "hw/acpi/wdat.h"
+#include "hw/watchdog/sbsa_gwdt.h"
+
+#define GWDT_REG(base, reg_offset, reg_width) { \
+                 .space_id = AML_AS_SYSTEM_MEMORY, \
+                 .address = base + reg_offset, .bit_width = reg_width, \
+                 .access_width = AML_DWORD_ACC };
+
+/*
+ *   "Hardware Watchdog Timers Design Specification"
+ *       https://uefi.org/acpi 'Watchdog Action Table (WDAT)'
+ */
+void build_gwdt_wdat(GArray *table_data, BIOSLinker *linker, const char 
*oem_id,
+                     const char *oem_table_id, uint64_t rbase, uint64_t cbase,
+                     uint64_t freq)
+{
+    AcpiTable table = { .sig = "WDAT", .rev = 1, .oem_id = oem_id,
+                        .oem_table_id = oem_table_id };
+
+    struct AcpiGenericAddress wrr =  GWDT_REG(rbase, 0x0, 32);
+    struct AcpiGenericAddress wor_l =  GWDT_REG(cbase, SBSA_GWDT_WOR, 32);
+    struct AcpiGenericAddress wcs =  GWDT_REG(cbase, SBSA_GWDT_WCS, 32);
+
+    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 */
+    /*
+     * WDAT spec suports only 1KHz or more coarse watchdog timer,
+     * Set resolution to minimum supported 1ms.
+     * Before starting watchdog Windows set countdown value to 5min.
+     */
+    g_assert(freq <= 1000);
+    build_append_int_noprefix(table_data, 1, 4);/* Timer Period, ms */
+    /*
+     * Needs to be more than 4min, otherwise Windows 11 won't start watchdog.
+     * Set max to limits to arbitrary max 10min and min to 5sec.
+     */
+    build_append_int_noprefix(table_data, 600 * freq, 4);/* Maximum Count */
+    build_append_int_noprefix(table_data, 5 * freq, 4);  /* Minimum Count */
+    /*
+     * WATCHDOG_ENABLED
+     */
+    build_append_int_noprefix(table_data, 0x81, 1); /* Watchdog Flags */
+    build_append_int_noprefix(table_data, 0, 3);    /* Reserved */
+    /*
+     * watchdog instruction entries
+     */
+    build_append_int_noprefix(table_data, 8, 4);
+    /* Action table */
+    build_append_wdat_ins(table_data, WDAT_ACTION_QUERY_RUNNING_STATE,
+        WDAT_INS_READ_VALUE,
+        wcs, 0x1, 0x1);
+    build_append_wdat_ins(table_data, WDAT_ACTION_RESET,
+        WDAT_INS_WRITE_VALUE,
+        wrr, 0x1, 0x7);
+    build_append_wdat_ins(table_data, WDAT_ACTION_SET_COUNTDOWN_PERIOD,
+        WDAT_INS_WRITE_COUNTDOWN,
+        wor_l, 0, 0xffffffff);
+    build_append_wdat_ins(table_data, WDAT_ACTION_SET_RUNNING_STATE,
+        WDAT_INS_WRITE_VALUE | WDAT_INS_PRESERVE_REGISTER,
+        wcs, 1, 0x00000001);
+    build_append_wdat_ins(table_data, WDAT_ACTION_QUERY_STOPPED_STATE,
+        WDAT_INS_READ_VALUE,
+        wcs, 0x0, 0x00000001);
+    build_append_wdat_ins(table_data, WDAT_ACTION_SET_STOPPED_STATE,
+        WDAT_INS_WRITE_VALUE | WDAT_INS_PRESERVE_REGISTER,
+        wcs, 0x0, 0x00000001);
+    build_append_wdat_ins(table_data, WDAT_ACTION_QUERY_WATCHDOG_STATUS,
+        WDAT_INS_READ_VALUE,
+        wcs, 0x4, 0x00000004);
+    build_append_wdat_ins(table_data, WDAT_ACTION_SET_WATCHDOG_STATUS,
+        WDAT_INS_WRITE_VALUE | WDAT_INS_PRESERVE_REGISTER,
+        wrr, 0x4, 0x4);
+
+    acpi_table_end(linker, &table);
+}
diff --git a/hw/arm/Kconfig b/hw/arm/Kconfig
index c66c452737..1222efadd1 100644
--- a/hw/arm/Kconfig
+++ b/hw/arm/Kconfig
@@ -36,6 +36,7 @@ config ARM_VIRT
     select VIRTIO_MEM_SUPPORTED
     select ACPI_CXL
     select ACPI_HMAT
+    select WDT_SBSA
 
 config CUBIEBOARD
     bool
diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
index c145678185..51a1c040a4 100644
--- a/hw/arm/virt-acpi-build.c
+++ b/hw/arm/virt-acpi-build.c
@@ -64,6 +64,7 @@
 #include "hw/virtio/virtio-acpi.h"
 #include "target/arm/cpu.h"
 #include "target/arm/multiprocessing.h"
+#include "hw/acpi/wdat-gwdt.h"
 
 #define ARM_SPI_BASE 32
 
@@ -1270,6 +1271,21 @@ void virt_acpi_build(VirtMachineState *vms, 
AcpiBuildTables *tables)
     acpi_add_table(table_offsets, tables_blob);
     build_madt(tables_blob, tables->linker, vms);
 
+    acpi_add_table(table_offsets, tables_blob);
+    if (ms->acpi_watchdog) {
+        uint64_t freq;
+
+        freq = object_property_get_uint(
+            object_resolve_type_unambiguous(TYPE_WDT_SBSA, &error_abort),
+            "clock-frequency", &error_abort);
+
+        build_gwdt_wdat(tables_blob, tables->linker,
+                        vms->oem_id, vms->oem_table_id,
+                        vms->memmap[VIRT_GWDT_REFRESH].base,
+                        vms->memmap[VIRT_GWDT_CONTROL].base,
+                        freq);
+    }
+
     if (!vmc->no_cpu_topology) {
         acpi_add_table(table_offsets, tables_blob);
         build_pptt(tables_blob, tables->linker, ms,
diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 390845c503..caf5700ed2 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -93,6 +93,7 @@
 #include "hw/cxl/cxl.h"
 #include "hw/cxl/cxl_host.h"
 #include "qemu/guest-random.h"
+#include "hw/watchdog/sbsa_gwdt.h"
 
 static GlobalProperty arm_virt_compat[] = {
     { TYPE_VIRTIO_IOMMU_PCI, "aw-bits", "48" },
@@ -194,6 +195,8 @@ static const MemMapEntry base_memmap[] = {
     [VIRT_PVTIME] =             { 0x090a0000, 0x00010000 },
     [VIRT_SECURE_GPIO] =        { 0x090b0000, 0x00001000 },
     [VIRT_ACPI_PCIHP] =         { 0x090c0000, ACPI_PCIHP_SIZE },
+    [VIRT_GWDT_REFRESH] =       { 0x090d0000, 0x00001000 },
+    [VIRT_GWDT_CONTROL] =       { 0x090d1000, 0x00001000 },
     [VIRT_MMIO] =               { 0x0a000000, 0x00000200 },
     /* ...repeating for a total of NUM_VIRTIO_TRANSPORTS, each of that size */
     [VIRT_PLATFORM_BUS] =       { 0x0c000000, 0x02000000 },
@@ -245,12 +248,32 @@ static const int a15irqmap[] = {
     [VIRT_GPIO] = 7,
     [VIRT_UART1] = 8,
     [VIRT_ACPI_GED] = 9,
+    [VIRT_GWDT_WS0] = 10,
     [VIRT_MMIO] = 16, /* ...to 16 + NUM_VIRTIO_TRANSPORTS - 1 */
     [VIRT_GIC_V2M] = 48, /* ...to 48 + NUM_GICV2M_SPIS - 1 */
     [VIRT_SMMU] = 74,    /* ...to 74 + NUM_SMMU_IRQS - 1 */
     [VIRT_PLATFORM_BUS] = 112, /* ...to 112 + PLATFORM_BUS_NUM_IRQS -1 */
 };
 
+static void create_wdt(const VirtMachineState *vms)
+{
+    hwaddr rbase = vms->memmap[VIRT_GWDT_REFRESH].base;
+    hwaddr cbase = vms->memmap[VIRT_GWDT_CONTROL].base;
+    int irq = vms->irqmap[VIRT_GWDT_WS0];
+    DeviceState *dev = qdev_new(TYPE_WDT_SBSA);
+    SysBusDevice *s = SYS_BUS_DEVICE(dev);
+
+    /*
+     * Set watchdog tick freq to 1Kz as it's the max WDAT driver
+     * is able to handle.
+     */
+    qdev_prop_set_uint64(dev, "clock-frequency", 1000 /* 1KHz */);
+    sysbus_realize_and_unref(s, &error_fatal);
+    sysbus_mmio_map(s, 0, rbase);
+    sysbus_mmio_map(s, 1, cbase);
+    sysbus_connect_irq(s, 0, qdev_get_gpio_in(vms->gic, irq));
+}
+
 static void create_randomness(MachineState *ms, const char *node)
 {
     struct {
@@ -2515,6 +2538,9 @@ static void machvirt_init(MachineState *machine)
     vms->highmem_ecam &= (!firmware_loaded || aarch64);
 
     create_rtc(vms);
+    if (machine->acpi_watchdog) {
+        create_wdt(vms);
+    }
 
     create_pcie(vms);
     create_cxl_host_reg_region(vms);
-- 
2.47.3


Reply via email to