Re: [Qemu-ppc] [PATCH 4/4] Enable kvm emulated watchdog

[Bhushan Bharat-R65777]

> -----Original Message-----
> From: Alexander Graf [mailto:address@hidden
> Sent: Wednesday, August 01, 2012 7:57 AM
> To: Bhushan Bharat-R65777
> Cc: address@hidden List; address@hidden; Bhushan Bharat-R65777;
> qemu-devel qemu-devel; KVM list
> Subject: Re: [PATCH 4/4] Enable kvm emulated watchdog
> 
> 
> On 20.07.2012, at 07:23, Bharat Bhushan wrote:
> 
> > Enable the KVM emulated watchdog if KVM supports (use the capability
> > enablement in watchdog handler). Also watchdog exit
> > (KVM_EXIT_WATCHDOG) handling is added.
> > Watchdog state machine is cleared whenever VM state changes to running.
> > This is to handle the cases like return from debug halt etc.
> >
> > Signed-off-by: Bharat Bhushan <address@hidden>
> > ---
> > v4: Enbale watchdog support only when user specifies watchdog-action
> >    Earlier this was [3/3] of the patch series. Now because i separated
> >    linux-header updation in separate patch, so this become [4/4]
> >
> > v3:
> > - TSR clearing is removed in whatchdog exit handling as this is
> >   no more needed.
> >
> > v2:
> > - Merged ([PATCH 3/4] Watchdog exit handling support) and
> >   ([PATCH 4/4] Enable to use kvm emulated watchdog)
> > - Clear watchdog state machine when VM state changes to running.
> >
> > hw/ppc_booke.c   |    5 ++++
> > sysemu.h         |    1 +
> > target-ppc/cpu.h |    1 +
> > target-ppc/kvm.c |   69 
> > ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> > vl.c             |    2 +
> > 5 files changed, 78 insertions(+), 0 deletions(-)
> >
> > diff --git a/hw/ppc_booke.c b/hw/ppc_booke.c index 837a5b6..478dbcd
> > 100644
> > --- a/hw/ppc_booke.c
> > +++ b/hw/ppc_booke.c
> > @@ -203,6 +203,11 @@ static void booke_wdt_cb(void *opaque)
> >                              booke_timer->wdt_timer); }
> >
> > +void ppc_booke_watchdog_clear_tsr(CPUPPCState *env, target_ulong tsr)
> > +{
> > +    env->spr[SPR_BOOKE_TSR] = tsr & ~(TSR_ENW | TSR_WIS |
> > +TSR_WRS_MASK); }
> > +
> > void store_booke_tsr(CPUPPCState *env, target_ulong val) {
> >     env->spr[SPR_BOOKE_TSR] &= ~val;
> > diff --git a/sysemu.h b/sysemu.h
> > index bc2c788..fc388b7 100644
> > --- a/sysemu.h
> > +++ b/sysemu.h
> > @@ -131,6 +131,7 @@ extern uint8_t *boot_splash_filedata; extern int
> > boot_splash_filedata_size; extern uint8_t qemu_extra_params_fw[2];
> > extern QEMUClock *rtc_clock;
> > +extern int enable_watchdog_support;
> >
> > #define MAX_NODES 64
> > extern int nb_numa_nodes;
> > diff --git a/target-ppc/cpu.h b/target-ppc/cpu.h index
> > ca2fc21..163389a 100644
> > --- a/target-ppc/cpu.h
> > +++ b/target-ppc/cpu.h
> > @@ -1191,6 +1191,7 @@ void store_40x_dbcr0 (CPUPPCState *env, uint32_t
> > val); void store_40x_sler (CPUPPCState *env, uint32_t val); void
> > store_booke_tcr (CPUPPCState *env, target_ulong val); void
> > store_booke_tsr (CPUPPCState *env, target_ulong val);
> > +void ppc_booke_watchdog_clear_tsr(CPUPPCState *env, target_ulong
> > +tsr);
> > void booke206_flush_tlb(CPUPPCState *env, int flags, const int
> > check_iprot); target_phys_addr_t booke206_tlb_to_page_size(CPUPPCState
> > *env, ppcmas_tlb_t *tlb); int ppcmas_tlb_check(CPUPPCState *env,
> > ppcmas_tlb_t *tlb, diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
> > index b6ef72d..0226b5e 100644
> > --- a/target-ppc/kvm.c
> > +++ b/target-ppc/kvm.c
> > @@ -32,6 +32,7 @@
> > #include "device_tree.h"
> > #include "hw/sysbus.h"
> > #include "hw/spapr.h"
> > +#include "hw/watchdog.h"
> >
> > #include "hw/sysbus.h"
> > #include "hw/spapr.h"
> > @@ -60,6 +61,7 @@ static int cap_booke_sregs; static int cap_ppc_smt;
> > static int cap_ppc_rma; static int cap_spapr_tce;
> > +static int cap_ppc_watchdog;
> >
> > /* XXX We have a race condition where we actually have a level triggered
> >  *     interrupt, but the infrastructure can't expose that yet, so the guest
> > @@ -86,6 +88,7 @@ int kvm_arch_init(KVMState *s)
> >     cap_ppc_smt = kvm_check_extension(s, KVM_CAP_PPC_SMT);
> >     cap_ppc_rma = kvm_check_extension(s, KVM_CAP_PPC_RMA);
> >     cap_spapr_tce = kvm_check_extension(s, KVM_CAP_SPAPR_TCE);
> > +    cap_ppc_watchdog = kvm_check_extension(s, KVM_CAP_PPC_BOOKE_WATCHDOG);
> >
> >     if (!cap_interrupt_level) {
> >         fprintf(stderr, "KVM: Couldn't find level irq capability. Expect 
> > the "
> > @@ -168,6 +171,30 @@ static int kvm_booke206_tlb_init(CPUPPCState *env)
> >     return 0;
> > }
> >
> > +static int kvm_watchdog_enable(CPUPPCState *env)
> > +{
> > +    int ret;
> > +    struct kvm_enable_cap encap = {};
> > +
> > +    if (!kvm_enabled()) {
> > +        return 0;
> > +    }
> > +
> > +    if (!cap_ppc_watchdog) {
> > +        printf("warning: KVM does not support watchdog");
> > +        return 0;
> > +    }
> > +
> > +    encap.cap = KVM_CAP_PPC_BOOKE_WATCHDOG;
> > +    ret = kvm_vcpu_ioctl(env, KVM_ENABLE_CAP, &encap);
> > +    if (ret < 0) {
> > +        fprintf(stderr, "%s: couldn't enable KVM_CAP_PPC_BOOKE_WATCHDOG:
> %s\n",
> > +                __func__, strerror(-ret));
> > +        return ret;
> > +    }
> > +
> > +    return ret;
> > +}
> >
> > #if defined(TARGET_PPC64)
> > static void kvm_get_fallback_smmu_info(CPUPPCState *env,
> > @@ -371,6 +398,32 @@ static inline void kvm_fixup_page_sizes(CPUPPCState 
> > *env)
> >
> > #endif /* !defined (TARGET_PPC64) */
> >
> > +static void cpu_state_change_handler(void *opaque, int running, RunState
> state)
> > +{
> > +    CPUPPCState *env = opaque;
> > +
> > +    struct kvm_sregs sregs;
> 
> = { };
> 
> > +
> > +    if (!running)
> > +        return;
> 
> Did you run checkpatch.pl? You're also missing a comment here which case we 
> want
> to act upon.
> 
> > +
> > +    /*
> > +     * Clear watchdog interrupt condition by clearing TSR.
> > +     * Similar logic needed to be implemented for watchdog
> > +     * emulation in qemu.
> > +     */
> > +    if (cap_booke_sregs && cap_ppc_watchdog) {
> > +        kvm_vcpu_ioctl(env, KVM_GET_SREGS, &sregs);
> > +
> > +        /* Clear TSR.ENW, TSR.WIS and TSR.WRS */
> > +        ppc_booke_watchdog_clear_tsr(env, sregs.u.e.tsr);
> > +        sregs.u.e.tsr = env->spr[SPR_BOOKE_TSR];
> > +        sregs.u.e.update_special = KVM_SREGS_E_UPDATE_TSR;
> > +
> > +        kvm_vcpu_ioctl(env, KVM_SET_SREGS, &sregs);
> 
> I'd prefer to see that logic implemented in the booke timer code with some
> special case around it for the kvm enabled case. But the event action is
> independent of kvm.

You want the logic inside the if (cap_booke_sregs && cap_ppc_watchdog) { } or 
complete function moved to hw/ppc_booke.c ?

> 
> > +    }
> > +}
> > +
> > int kvm_arch_init_vcpu(CPUPPCState *cenv)
> > {
> >     int ret;
> > @@ -384,6 +437,15 @@ int kvm_arch_init_vcpu(CPUPPCState *cenv)
> >         return ret;
> >     }
> >
> > +    if (enable_watchdog_support) {
> > +        ret = kvm_watchdog_enable(cenv);
> 
> Do you think this is a good idea? Why would real hardware not implement a
> watchdog just because the user didn't select an action?

If there is no watchdog action then why we want to run watchdog timer?

> 
> Also, we probably want this called from the booke watchdog initialization 
> code.

You mean hw/ppc_booke.c, right?

> 
> > +        if (ret) {
> > +            return ret;
> > +        }
> > +    }
> > +
> > +    qemu_add_vm_change_state_handler(cpu_state_change_handler, cenv);
> > +
> >     idle_timer = qemu_new_timer_ns(vm_clock, kvm_kick_env, cenv);
> >
> >     /* Some targets support access to KVM's guest TLB. */
> > @@ -769,6 +831,13 @@ int kvm_arch_handle_exit(CPUPPCState *env, struct 
> > kvm_run
> *run)
> >         ret = 1;
> >         break;
> > #endif
> > +#ifdef KVM_EXIT_WATCHDOG
> > +    case KVM_EXIT_WATCHDOG:
> > +        dprintf("handle watchdog expiry\n");
> > +        watchdog_perform_action();
> > +        ret = 0;
> > +        break;
> > +#endif
> >     default:
> >         fprintf(stderr, "KVM: unknown exit reason %d\n", run->exit_reason);
> >         ret = -1;
> > diff --git a/vl.c b/vl.c
> > index 1329c30..f5427a8 100644
> > --- a/vl.c
> > +++ b/vl.c
> > @@ -213,6 +213,7 @@ int no_shutdown = 0;
> > int cursor_hide = 1;
> > int graphic_rotate = 0;
> > const char *watchdog;
> > +int enable_watchdog_support = 0;
> 
> This is just plain ugly.
> 
> How do the other watchdog implementations today know if they're supposed to be
> used? And do we even need this bit?

If we call watchdog enable from hw/ppc_booke.c then we do not this.

Thanks
-Bharat

> 
> > QEMUOptionRom option_rom[MAX_OPTION_ROMS];
> > int nb_option_roms;
> > int semihosting_enabled = 0;
> > @@ -2888,6 +2889,7 @@ int main(int argc, char **argv, char **envp)
> >                     fprintf(stderr, "Unknown -watchdog-action parameter\n");
> >                     exit(1);
> >                 }
> > +                enable_watchdog_support = 1;
> >                 break;
> >             case QEMU_OPTION_virtiocon:
> >                 add_device_config(DEV_VIRTCON, optarg);
> 
> PS: Please CC qemu-devel and address@hidden for the next round and follow-up 
> mails.
> 
> 
> Alex
>