arm: virt: add support for WDAT based watchdog
Add WDAT handling for sbsa-gwdt on arm/virt machine. WDAT mode is enabled by 'wdat' option: ex: "-device sbsa-gwdt,wdat=on" When WDAT is enabled: - Build the WDAT ACPI table instead of the GTDT watchdog entry, since they are mutually exclusive due to different timer resolution (WDAT uses 1 kHz vs GTDT's system counter frequency). - Skip FDT watchdog node creation, as the DT-based Linux driver would use the system counter frequency which doesn't match the WDAT-mode 1 kHz clock. Signed-off-by: Igor Mammedov <imammedo@redhat.com> Reviewed-by: Eric Auger <eric.auger@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Message-ID: <20260702145856.1539572-8-imammedo@redhat.com>
Igor Mammedov committed
Jul 2, 2026 at 16:58 UTC
285bc90d5b31775b7803e50822930a2914bf42de
3 files changed
+49
-12
docs/system/arm/virt.rst
+15
@@ -323,6 +323,21 @@ using ``-device sbsa-gwdt``. It is only supported on the virt machine,
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which wires up statically assigned MMIO regions and IRQs via
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machine-specific plug handlers.
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+Two modes are available:
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+
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+Native mode (default)
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+ The watchdog is described via the ACPI GTDT table and FDT, using
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+ the system counter frequency. Example::
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+
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+ -device sbsa-gwdt
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+
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+WDAT mode
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+ The watchdog is described via the ACPI WDAT table (no FDT node),
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+ using a 1 kHz timer frequency. WDAT and GTDT watchdog entries are
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+ mutually exclusive. Example::
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+
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+ -device sbsa-gwdt,wdat=on
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+
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Linux guest kernel configuration
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""""""""""""""""""""""""""""""""
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hw/arm/virt-acpi-build.c
+26
-8
@@ -65,6 +65,7 @@
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#include "target/arm/cpu.h"
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#include "target/arm/multiprocessing.h"
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#include "hw/watchdog/sbsa_gwdt.h"
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+#include "hw/acpi/wdat-gwdt.h"
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#include "smmuv3-accel.h"
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#include "tegra241-cmdqv.h"
@@ -859,7 +860,8 @@ build_srat(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
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* 5.2.25 Generic Timer Description Table (GTDT)
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*/
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static void
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-build_gtdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
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+build_gtdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms,
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+ bool add_watchdog)
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{
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/*
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* Table 5-117 Flag Definitions
@@ -870,7 +872,6 @@ build_gtdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
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AcpiTable table = { .sig = "GTDT", .rev = 3, .oem_id = vms->oem_id,
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.oem_table_id = vms->oem_table_id };
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uint32_t gtdt_start = table_data->len;
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- Object *wdt = object_resolve_type_unambiguous(TYPE_WDT_SBSA, NULL);
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acpi_table_begin(&table, table_data);
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@@ -903,12 +904,12 @@ build_gtdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
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build_append_int_noprefix(table_data, 0xFFFFFFFFFFFFFFFF, 8);
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/* Platform Timer Count */
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- build_append_int_noprefix(table_data, wdt ? 1 : 0, 4);
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+ build_append_int_noprefix(table_data, add_watchdog ? 1 : 0, 4);
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/* Platform Timer Offset */
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build_append_int_noprefix(table_data,
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- wdt ? (table_data->len - gtdt_start) +
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- 4 + 4 + 4 /* len of this & following 2 fields to skip */
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- : 0, 4);
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+ add_watchdog ? (table_data->len - gtdt_start) +
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+ 4 + 4 + 4 /* len of this & following 2 fields to skip */
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+ : 0, 4);
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if (vms->ns_el2_virt_timer_irq) {
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/* Virtual EL2 Timer GSIV */
@@ -921,7 +922,7 @@ build_gtdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
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}
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/* ACPI 6.5 spec: 5.2.25.2 ARM Generic Watchdog Structure (Table 5-124) */
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- if (wdt) {
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+ if (add_watchdog) {
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hwaddr rbase = vms->memmap[VIRT_GWDT_REFRESH].base;
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hwaddr cbase = vms->memmap[VIRT_GWDT_CONTROL].base;
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int irq = ARM_SPI_BASE + vms->irqmap[VIRT_GWDT_WS0];
@@ -1332,13 +1333,19 @@ void virt_acpi_build(VirtMachineState *vms, AcpiBuildTables *tables)
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VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms);
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GArray *table_offsets;
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unsigned dsdt, xsdt;
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+ bool has_wdat = false;
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GArray *tables_blob = tables->table_data;
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MachineState *ms = MACHINE(vms);
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CPUCoreCaches caches[CPU_MAX_CACHES];
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unsigned int num_caches;
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+ Object *wdt = object_resolve_type_unambiguous(TYPE_WDT_SBSA, NULL);
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num_caches = virt_get_caches(vms, caches);
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+ if (wdt) {
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+ has_wdat = object_property_get_bool(wdt, "wdat", &error_abort);
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+ }
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+
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table_offsets = g_array_new(false, true /* clear */,
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sizeof(uint32_t));
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@@ -1357,6 +1364,17 @@ void virt_acpi_build(VirtMachineState *vms, AcpiBuildTables *tables)
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acpi_add_table(table_offsets, tables_blob);
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build_madt(tables_blob, tables->linker, vms);
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+ acpi_add_table(table_offsets, tables_blob);
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+ if (wdt && has_wdat) {
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+ uint64_t freq = object_property_get_uint(wdt, "clock-frequency",
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+ &error_abort);
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+ build_gwdt_wdat(tables_blob, tables->linker,
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+ vms->oem_id, vms->oem_table_id,
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+ vms->memmap[VIRT_GWDT_REFRESH].base,
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+ vms->memmap[VIRT_GWDT_CONTROL].base,
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+ freq);
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+ }
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+
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if (!vmc->no_cpu_topology) {
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acpi_add_table(table_offsets, tables_blob);
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build_pptt(tables_blob, tables->linker, ms, vms->oem_id,
@@ -1364,7 +1382,7 @@ void virt_acpi_build(VirtMachineState *vms, AcpiBuildTables *tables)
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}
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acpi_add_table(table_offsets, tables_blob);
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- build_gtdt(tables_blob, tables->linker, vms);
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+ build_gtdt(tables_blob, tables->linker, vms, wdt && !has_wdat);
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acpi_add_table(table_offsets, tables_blob);
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{
hw/arm/virt.c
+8
-4
@@ -3846,10 +3846,12 @@ static void virt_machine_device_pre_plug_cb(HotplugHandler *hotplug_dev,
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qdev_prop_set_array(dev, "reserved-regions", reserved_regions);
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g_free(resv_prop_str);
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} else if (object_dynamic_cast(OBJECT(dev), TYPE_WDT_SBSA)) {
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- uint64_t cntfrq = object_property_get_int(OBJECT(qemu_get_cpu(0)),
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- "cntfrq", &error_abort);
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+ if (!object_property_get_bool(OBJECT(dev), "wdat", &error_abort)) {
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+ uint64_t cntfrq = object_property_get_int(OBJECT(qemu_get_cpu(0)),
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+ "cntfrq", &error_abort);
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- qdev_prop_set_uint64(dev, "clock-frequency", cntfrq);
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+ qdev_prop_set_uint64(dev, "clock-frequency", cntfrq);
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+ }
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} else if (object_dynamic_cast(OBJECT(dev), TYPE_ARM_SMMUV3)) {
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if (vms->legacy_smmuv3_present || vms->iommu == VIRT_IOMMU_VIRTIO) {
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error_setg(errp, "virt machine already has %s set. "
@@ -3911,7 +3913,9 @@ static void virt_machine_device_plug_cb(HotplugHandler *hotplug_dev,
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sysbus_mmio_map(s, 1, cbase);
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sysbus_connect_irq(s, 0, qdev_get_gpio_in(vms->gic, irq));
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- create_gwdt_dt_bindings(vms);
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+ if (!object_property_get_bool(OBJECT(dev), "wdat", &error_abort)) {
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+ create_gwdt_dt_bindings(vms);
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+ }
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}
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if (vms->platform_bus_dev) {