Re: [PATCH qemu v2 2/2] ppc/spapr: Implement H_WATCHDOG

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 6/20/22 16:23, Cédric Le Goater wrote:
> On 6/20/22 05:13, Alexey Kardashevskiy wrote:
>>
>>
>> On 6/18/22 21:01, Cédric Le Goater wrote:
>>> On 6/17/22 08:07, Alexey Kardashevskiy wrote:
>>>> The new PAPR 2.12 defines a watchdog facility managed via the new
>>>> H_WATCHDOG hypercall.
>>>>
>>>> This adds H_WATCHDOG support which a proposed driver for pseries uses:
>>>> https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=303120
>>>>
>>>> This was tested by running QEMU with a debug kernel and command line:
>>>> -append \
>>>>   "pseries-wdt.timeout=60 pseries-wdt.nowayout=1 pseries-wdt.action=2"
>>>>
>>>> and running "echo V > /dev/watchdog0" inside the VM.
>>>>
>>>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>>>> ---
>>>> Changes:
>>>> v2:
>>>> * QOM'ed timers, "action" and "expire" are available via QMP
>>>> * removed @timeout from SpaprWatchdog
>>>> * moved the driver to hw/watchdog
>>>> * fixed error handling in the hcall handler
>>>> * used new SETFIELD/GETFIELD
>>>> ---
>>>>   include/hw/ppc/spapr.h       |  29 +++-
>>>>   hw/ppc/spapr.c               |   4 +
>>>>   hw/watchdog/spapr_watchdog.c | 248 
>>>> +++++++++++++++++++++++++++++++++++
>>>>   hw/watchdog/meson.build      |   1 +
>>>>   hw/watchdog/trace-events     |   7 +
>>>>   5 files changed, 288 insertions(+), 1 deletion(-)
>>>>   create mode 100644 hw/watchdog/spapr_watchdog.c
>>>>
>>>> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
>>>> index 072dda2c7265..ef1e38abd5c7 100644
>>>> --- a/include/hw/ppc/spapr.h
>>>> +++ b/include/hw/ppc/spapr.h
>>>> @@ -164,6 +164,25 @@ struct SpaprMachineClass {
>>>>       SpaprIrq *irq;
>>>>   };
>>>> +#define WDT_MAX_WATCHDOGS       4      /* Maximum number of 
>>>> watchdog devices */
>>>> +
>>>> +#define WDT_HARD_POWER_OFF      0
>>>> +#define WDT_HARD_RESTART        1
>>>> +#define WDT_DUMP_RESTART        2
>>>> +
>>>> +#define TYPE_SPAPR_WDT "spapr-wdt"
>>>> +OBJECT_DECLARE_SIMPLE_TYPE(SpaprWatchdog, SPAPR_WDT)
>>>> +
>>>> +typedef struct SpaprWatchdog {
>>>> +    /*< private >*/
>>>> +    DeviceState parent_obj;
>>>> +    /*< public >*/
>>>> +
>>>> +    unsigned num;
>>>
>>> uint8_t should be enough no ? I see num is only used for trace events.
>>
>>
>> It should but why? It is not migrating, and using uint8_t creates 
>> alignment gap here, and no benefit :) And I am removing it anyway, see 
>> below.
>>
>>>
>>>> +    QEMUTimer timer;
>>>> +    uint8_t action;
>>>> +} SpaprWatchdog;
>>>> +
>>>>   /**
>>>>    * SpaprMachineState:
>>>>    */
>>>> @@ -264,6 +283,8 @@ struct SpaprMachineState {
>>>>       uint32_t 
>>>> FORM2_assoc_array[NUMA_NODES_MAX_NUM][FORM2_NUMA_ASSOC_SIZE];
>>>>       Error *fwnmi_migration_blocker;
>>>> +
>>>> +    SpaprWatchdog wds[WDT_MAX_WATCHDOGS];
>>>>   };
>>>>   #define H_SUCCESS         0
>>>> @@ -344,6 +365,7 @@ struct SpaprMachineState {
>>>>   #define H_P7              -60
>>>>   #define H_P8              -61
>>>>   #define H_P9              -62
>>>> +#define H_NOOP            -63
>>>>   #define H_UNSUPPORTED     -67
>>>>   #define H_OVERLAP         -68
>>>>   #define H_UNSUPPORTED_FLAG -256
>>>> @@ -564,8 +586,9 @@ struct SpaprMachineState {
>>>>   #define H_SCM_HEALTH            0x400
>>>>   #define H_RPT_INVALIDATE        0x448
>>>>   #define H_SCM_FLUSH             0x44C
>>>> +#define H_WATCHDOG              0x45C
>>>> -#define MAX_HCALL_OPCODE        H_SCM_FLUSH
>>>> +#define MAX_HCALL_OPCODE        H_WATCHDOG
>>>>   /* The hcalls above are standardized in PAPR and implemented by pHyp
>>>>    * as well.
>>>> @@ -1027,6 +1050,7 @@ extern const VMStateDescription 
>>>> vmstate_spapr_cap_large_decr;
>>>>   extern const VMStateDescription vmstate_spapr_cap_ccf_assist;
>>>>   extern const VMStateDescription vmstate_spapr_cap_fwnmi;
>>>>   extern const VMStateDescription vmstate_spapr_cap_rpt_invalidate;
>>>> +extern const VMStateDescription vmstate_spapr_wdt;
>>>>   static inline uint8_t spapr_get_cap(SpaprMachineState *spapr, int 
>>>> cap)
>>>>   {
>>>> @@ -1063,4 +1087,7 @@ target_ulong 
>>>> spapr_vof_client_architecture_support(MachineState *ms,
>>>>                                                      target_ulong 
>>>> ovec_addr);
>>>>   void spapr_vof_client_dt_finalize(SpaprMachineState *spapr, void 
>>>> *fdt);
>>>> +/* H_WATCHDOG */
>>>> +void spapr_watchdog_init(SpaprMachineState *spapr);
>>>> +
>>>>   #endif /* HW_SPAPR_H */
>>>> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
>>>> index fd4942e8813c..9a5382d5270f 100644
>>>> --- a/hw/ppc/spapr.c
>>>> +++ b/hw/ppc/spapr.c
>>>> @@ -898,6 +898,8 @@ static void spapr_dt_rtas(SpaprMachineState 
>>>> *spapr, void *fdt)
>>>>           add_str(hypertas, "hcall-hpt-resize");
>>>>       }
>>>> +    add_str(hypertas, "hcall-watchdog");
>>>> +
>>>>       _FDT(fdt_setprop(fdt, rtas, "ibm,hypertas-functions",
>>>>                        hypertas->str, hypertas->len));
>>>>       g_string_free(hypertas, TRUE);
>>>> @@ -3051,6 +3053,8 @@ static void spapr_machine_init(MachineState 
>>>> *machine)
>>>>           spapr->vof->fw_size = fw_size; /* for claim() on itself */
>>>>           spapr_register_hypercall(KVMPPC_H_VOF_CLIENT, 
>>>> spapr_h_vof_client);
>>>>       }
>>>> +
>>>> +    spapr_watchdog_init(spapr);
>>>>   }
>>>>   #define DEFAULT_KVM_TYPE "auto"
>>>> diff --git a/hw/watchdog/spapr_watchdog.c 
>>>> b/hw/watchdog/spapr_watchdog.c
>>>> new file mode 100644
>>>> index 000000000000..aeaf7c52cbad
>>>> --- /dev/null
>>>> +++ b/hw/watchdog/spapr_watchdog.c
>>>> @@ -0,0 +1,248 @@
>>>> +/*
>>>> + * This library is free software; you can redistribute it and/or
>>>> + * modify it under the terms of the GNU Lesser General Public
>>>> + * License as published by the Free Software Foundation; either
>>>> + * version 2.1 of the License, or (at your option) any later version.
>>>> + *
>>>> + * This library is distributed in the hope that it will be useful,
>>>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>>>> + * Lesser General Public License for more details.
>>>> + *
>>>> + * You should have received a copy of the GNU Lesser General Public
>>>> + * License along with this library; if not, see 
>>>> <http://www.gnu.org/licenses/>.
>>>> + */
>>>> +
>>>> +#include "qemu/osdep.h"
>>>> +#include "qapi/error.h"
>>>> +#include "target/ppc/cpu.h"
>>>> +#include "migration/vmstate.h"
>>>> +#include "trace.h"
>>>> +
>>>> +#include "hw/ppc/spapr.h"
>>>> +
>>>> +/*
>>>> + * Bits 47: "leaveOtherWatchdogsRunningOnTimeout", specified on
>>>> + * the "Start watchdog" operation,
>>>> + * 0 - stop out-standing watchdogs on timeout,
>>>> + * 1 - leave outstanding watchdogs running on timeout
>>>> + */
>>>> +#define PSERIES_WDTF_LEAVE_OTHER    PPC_BIT(47)
>>>> +
>>>> +/*    Bits 48-55: "operation" */
>>>> +#define PSERIES_WDTF_OP(op)             SETFIELD(PPC_BITMASK(48, 
>>>> 55), 0, (op))
>>>> +#define PSERIES_WDTF_OP_START           PSERIES_WDTF_OP(0x1)
>>>> +#define PSERIES_WDTF_OP_STOP            PSERIES_WDTF_OP(0x2)
>>>> +#define PSERIES_WDTF_OP_QUERY           PSERIES_WDTF_OP(0x3)
>>>> +#define PSERIES_WDTF_OP_QUERY_LPM       PSERIES_WDTF_OP(0x4)
>>>> +
>>>> +/*    Bits 56-63: "timeoutAction" */
>>>> +#define PSERIES_WDTF_ACTION(ac)         SETFIELD(PPC_BITMASK(56, 
>>>> 63), 0, (ac))
>>>> +#define PSERIES_WDTF_ACTION_HARD_POWER_OFF  PSERIES_WDTF_ACTION(0x1)
>>>> +#define PSERIES_WDTF_ACTION_HARD_RESTART    PSERIES_WDTF_ACTION(0x2)
>>>> +#define PSERIES_WDTF_ACTION_DUMP_RESTART    PSERIES_WDTF_ACTION(0x3)
>>>> +#define PSERIES_WDTF_RESERVED           PPC_BITMASK(0, 46)
>>>> +
>>>> +/*
>>>> + * For the "Query watchdog capabilities" operation, a uint64 structure
>>>> + * defined as:
>>>> + * Bits 0-15: The minimum supported timeout in milliseconds
>>>> + * Bits 16-31: The number of watchdogs supported
>>>> + * Bits 32-63: Reserved
>>>> + */
>>>> +#define PSERIES_WDTQ_MIN_TIMEOUT(ms)    SETFIELD(PPC_BITMASK(0, 
>>>> 15), 0, (ms))
>>>> +#define PSERIES_WDTQ_NUM(n)             SETFIELD(PPC_BITMASK(16, 
>>>> 31), 0, (n))
>>>> +
>>>> +/*
>>>> + * For the "Query watchdog LPM requirement" operation:
>>>> + * 1 = The given "watchdogNumber" must be stopped prior to suspending
>>>> + * 2 = The given "watchdogNumber" does not have to be stopped prior to
>>>> + * suspending
>>>> + */
>>>> +#define PSERIES_WDTQL_STOPPED               1
>>>> +#define PSERIES_WDTQL_QUERY_NOT_STOPPED     2
>>>> +
>>>> +#define WDT_MIN_TIMEOUT 1 /* 1ms */
>>>> +
>>>> +static void watchdog_expired(void *pw)
>>>> +{
>>>> +    struct SpaprWatchdog *w = pw;
>>>
>>> s/struct//
>>>
>>>> +    CPUState *cs;
>>>> +
>>>> +    trace_spapr_watchdog_expired(w->num, w->action);
>>>> +    switch (w->action) {
>>>> +    case WDT_HARD_POWER_OFF:
>>>> +        qemu_system_vmstop_request(RUN_STATE_SHUTDOWN);
>>>> +        break;
>>>> +    case WDT_HARD_RESTART:
>>>> +        qemu_system_reset_request(SHUTDOWN_CAUSE_GUEST_RESET);
>>>> +        break;
>>>> +    case WDT_DUMP_RESTART:
>>>> +        CPU_FOREACH(cs) {
>>>> +            async_run_on_cpu(cs, spapr_do_system_reset_on_cpu, 
>>>> RUN_ON_CPU_NULL);
>>>> +        }
>>>> +        break;
>>>> +    }
>>>> +}
>>>> +
>>>> +static target_ulong watchdog_stop(unsigned watchdogNumber,
>>>> +                                  struct SpaprWatchdog *w)
>>>> +{
>>>> +    target_ulong ret = H_NOOP;
>>>> +
>>>> +    if (timer_pending(&w->timer)) {
>>>> +        timer_del(&w->timer);
>>>> +        ret = H_SUCCESS;
>>>> +    }
>>>> +    trace_spapr_watchdog_stop(watchdogNumber, ret);
>>>> +
>>>> +    return ret;
>>>> +}
>>>> +
>>>> +static target_ulong h_watchdog(PowerPCCPU *cpu,
>>>> +                               SpaprMachineState *spapr,
>>>> +                               target_ulong opcode, target_ulong 
>>>> *args)
>>>> +{
>>>> +    target_ulong flags = args[0];
>>>> +    target_ulong watchdogNumber = args[1];
>>>> +    target_ulong timeoutInMs = args[2];
>>>> +    unsigned operation = flags & PSERIES_WDTF_OP(~0);
>>>> +    unsigned timeoutAction = flags & PSERIES_WDTF_ACTION(~0);
>>>> +    struct SpaprWatchdog *w;
>>>> +
>>>> +    if (flags & PSERIES_WDTF_RESERVED) {
>>>> +        return H_PARAMETER;
>>>> +    }
>>>> +
>>>> +    switch (operation) {
>>>> +    case PSERIES_WDTF_OP_START:
>>>> +        if (watchdogNumber > ARRAY_SIZE(spapr->wds)) {
>>>> +            return H_P2;
>>>> +        }
>>>> +        if (timeoutInMs <= WDT_MIN_TIMEOUT) {
>>>> +            return H_P3;
>>>> +        }
>>>> +
>>>> +        w = &spapr->wds[watchdogNumber - 1];
>>>
>>> So first index is 1 in PAPR ...
>>
>>
>> Yes, I thought I commented on this somewhere but lost in rebases.
>>
>>
>>>
>>>> +        switch (timeoutAction) {
>>>> +        case PSERIES_WDTF_ACTION_HARD_POWER_OFF:
>>>> +            w->action = WDT_HARD_POWER_OFF;
>>>> +            break;
>>>> +        case PSERIES_WDTF_ACTION_HARD_RESTART:
>>>> +            w->action = WDT_HARD_RESTART;
>>>> +            break;
>>>> +        case PSERIES_WDTF_ACTION_DUMP_RESTART:
>>>> +            w->action = WDT_DUMP_RESTART;
>>>> +            break;
>>>> +        default:
>>>> +            return H_PARAMETER;
>>>> +        }
>>>> +        timer_mod(&w->timer,
>>>> +                  qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + 
>>>> timeoutInMs);
>>>> +        trace_spapr_watchdog_start(flags, watchdogNumber, 
>>>> timeoutInMs);
>>>> +        break;
>>>> +    case PSERIES_WDTF_OP_STOP:
>>>> +        if (watchdogNumber == (uint64_t) ~0) {
>>>
>>> May be add a define for this special value. It's better for readability.
>>
>> Will do.
>>
>>
>>>> +            int i;
>>>> +
>>>> +            for (i = 1; i <= ARRAY_SIZE(spapr->wds); ++i) {
>>>> +                watchdog_stop(i, &spapr->wds[i - 1]);
>>>> +            }
>>>> +        } else if (watchdogNumber <= ARRAY_SIZE(spapr->wds)) {
>>>> +            watchdog_stop(watchdogNumber, 
>>>> &spapr->wds[watchdogNumber - 1]);
>>>> +        } else {
>>>> +            return H_P2;
>>>> +        }
>>>> +        break;
>>>> +    case PSERIES_WDTF_OP_QUERY:
>>>> +        args[0] = PSERIES_WDTQ_MIN_TIMEOUT(WDT_MIN_TIMEOUT) |
>>>> +            PSERIES_WDTQ_NUM(ARRAY_SIZE(spapr->wds));
>>>> +        trace_spapr_watchdog_query(args[0]);
>>>> +        break;
>>>> +    case PSERIES_WDTF_OP_QUERY_LPM:
>>>> +        if (watchdogNumber > ARRAY_SIZE(spapr->wds)) {
>>>> +            return H_P2;
>>>> +        }
>>>> +        args[0] = PSERIES_WDTQL_QUERY_NOT_STOPPED;
>>>> +        trace_spapr_watchdog_query_lpm(args[0]);
>>>> +        break;
>>>> +    default:
>>>> +        return H_PARAMETER;
>>>> +    }
>>>> +
>>>> +    return H_SUCCESS;
>>>> +}
>>>> +
>>>> +void spapr_watchdog_init(SpaprMachineState *spapr)
>>>
>>> This could have a 'Error **errp' parameter.
>>
>>
>> I was repeating somewhat similar spapr_rtc_create(), and the called - 
>> spapr_machine_init() - does not have *errp. Seems pointless as it 
>> fails - something is horrendously broken.
> 
> 
> Well, it's up to the caller to decide what to do in case of
> errors. If in this case, it is "log an error and exit",
> I would simply :
> 
>    spapr_watchdog_init(spapr, &error_fatal);
> 
> But it is not necessarily fatal to fail to initialize some
> device.

The device is so simple and not configurable via the command line that 
it is fatal. And it does not touch *errp anyway.

Passing errp also means spapr_watchdog_init() should do clean up of 
whatever it did in a loop before hitting the error, for example in this 
case - unrealize() previously realized watchdogs. This adds useless code 
as it is going to be fatal anyway. Thanks,


> 
>>
>>
>>>
>>>> +{
>>>> +    int i;
>>>> +
>>>> +    for (i = 0; i < ARRAY_SIZE(spapr->wds); ++i) {
>>>> +        char name[16];g_autofree char *name = 
>>>> g_strdup_printf("wdt%d", i + 1);
>>>
>>>> +        SpaprWatchdog *w = &spapr->wds[i];
>>>> +
>>>> +        w->num = i + 1;
>>>
>>> it should be a property.
>>
>> This cannot change and used only for tracing, and the QOM name has the 
>> number as well. I am replacing it with
>>
>> SpaprMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
>> unsigned num = w - spapr->wds;
>>
>> and removing the @num from the struct.
> 
> Nice !
> 
> Thanks
> 
> C.
> 
> 
>>
>> Thanks,
>>
>>>
>>> Thanks,
>>>
>>> C.
>>>
>>>> +        snprintf(name, sizeof(name) - 1, "wdt%d", i + 1);
>>>> +        object_initialize_child_with_props(OBJECT(spapr), name, w,
>>>> +                                           sizeof(SpaprWatchdog),
>>>> +                                           TYPE_SPAPR_WDT,
>>>> +                                           &error_fatal, NULL);
>>>> +        qdev_realize(DEVICE(w), NULL, &error_fatal);
>>>> +    }
>>>> +}
>>>> +
>>>> +static bool watchdog_needed(void *opaque)
>>>> +{
>>>> +    SpaprWatchdog *w = opaque;
>>>> +
>>>> +    return timer_pending(&w->timer);
>>>> +}
>>>> +
>>>> +static const VMStateDescription vmstate_wdt = {
>>>> +    .name = "spapr_watchdog",
>>>> +    .version_id = 1,
>>>> +    .minimum_version_id = 1,
>>>> +    .needed = watchdog_needed,
>>>> +    .fields = (VMStateField[]) {
>>>> +        VMSTATE_UINT8(action, SpaprWatchdog),
>>>> +        VMSTATE_TIMER(timer, SpaprWatchdog),
>>>> +        VMSTATE_END_OF_LIST()
>>>> +    }
>>>> +};
>>>> +
>>>> +static void spapr_wdt_realize(DeviceState *dev, Error **errp)
>>>> +{
>>>> +    SpaprWatchdog *w = SPAPR_WDT(dev);
>>>> +
>>>> +    timer_init_ms(&w->timer, QEMU_CLOCK_VIRTUAL, watchdog_expired, w);
>>>> +
>>>> +    object_property_add_uint64_ptr(OBJECT(dev), "expire",
>>>> +                                   (uint64_t *)&w->timer.expire_time,
>>>> +                                   OBJ_PROP_FLAG_READ);
>>>> +    object_property_add_uint8_ptr(OBJECT(dev), "action", &w->action,
>>>> +                                  OBJ_PROP_FLAG_READ);
>>>> +}
>>>> +
>>>> +static void spapr_wdt_class_init(ObjectClass *oc, void *data)
>>>> +{
>>>> +    DeviceClass *dc = DEVICE_CLASS(oc);
>>>> +
>>>> +    dc->renualize = spapr_wdt_realize;
>>>> +    dc->vmsd = &vmstate_wdt;
>>>> +    dc->user_creatable = false;
>>>> +}
>>>> +
>>>> +static const TypeInfo spapr_wdt_info = {
>>>> +    .name          = TYPE_SPAPR_WDT,
>>>> +    .parent        = TYPE_DEVICE,
>>>> +    .instance_size = sizeof(SpaprWatchdog),
>>>> +    .class_init    = spapr_wdt_class_init,
>>>> +};
>>>> +
>>>> +static void spapr_watchdog_register_types(void)
>>>> +{
>>>> +    spapr_register_hypercall(H_WATCHDOG, h_watchdog);
>>>> +    type_register_static(&spapr_wdt_info);
>>>> +}
>>>> +
>>>> +type_init(spapr_watchdog_register_types)
>>>> diff --git a/hw/watchdog/meson.build b/hw/watchdog/meson.build
>>>> index 054c403dea7c..8974b5cf4c8a 100644
>>>> --- a/hw/watchdog/meson.build
>>>> +++ b/hw/watchdog/meson.build
>>>> @@ -6,3 +6,4 @@ softmmu_ss.add(when: 'CONFIG_WDT_DIAG288', if_true: 
>>>> files('wdt_diag288.c'))
>>>>   softmmu_ss.add(when: 'CONFIG_ASPEED_SOC', if_true: 
>>>> files('wdt_aspeed.c'))
>>>>   softmmu_ss.add(when: 'CONFIG_WDT_IMX2', if_true: files('wdt_imx2.c'))
>>>>   softmmu_ss.add(when: 'CONFIG_WDT_SBSA', if_true: 
>>>> files('sbsa_gwdt.c'))
>>>> +specific_ss.add(when: 'CONFIG_PSERIES', if_true: 
>>>> files('spapr_watchdog.c'))
>>>> diff --git a/hw/watchdog/trace-events b/hw/watchdog/trace-events
>>>> index e7523e22aaf2..89ccbcfdfd20 100644
>>>> --- a/hw/watchdog/trace-events
>>>> +++ b/hw/watchdog/trace-events
>>>> @@ -9,3 +9,10 @@ cmsdk_apb_watchdog_lock(uint32_t lock) "CMSDK APB 
>>>> watchdog: lock %" PRIu32
>>>>   # wdt-aspeed.c
>>>>   aspeed_wdt_read(uint64_t addr, uint32_t size) "@0x%" PRIx64 " 
>>>> size=%d"
>>>>   aspeed_wdt_write(uint64_t addr, uint32_t size, uint64_t data) 
>>>> "@0x%" PRIx64 " size=%d value=0x%"PRIx64
>>>> +
>>>> +# spapr_watchdog.c
>>>> +spapr_watchdog_start(uint64_t flags, uint64_t num, uint64_t 
>>>> timeout) "Flags 0x%" PRIx64 " num=%" PRId64 " %" PRIu64 "ms"
>>>> +spapr_watchdog_stop(uint64_t num, uint64_t ret) "num=%" PRIu64 " 
>>>> ret=%" PRId64
>>>> +spapr_watchdog_query(uint64_t caps) "caps=0x%" PRIx64
>>>> +spapr_watchdog_query_lpm(uint64_t caps) "caps=0x%" PRIx64
>>>> +spapr_watchdog_expired(uint64_t num, unsigned action) "num=%" 
>>>> PRIu64 " action=%u"
>>
> 

-- 
Alexey