Re: [Qemu-devel] [PATCH 3/3] s390: add cpu reset handler

[Jens Freimann <jfrei@linux.vnet.ibm.com>]

On Fri, Dec 07, 2012 at 08:07:45PM +0100, Andreas Färber wrote:
> Am 07.12.2012 14:55, schrieb Jens Freimann:
> > Add a CPU reset handler to have all CPUs in a PoP compliant
> > state.
> > 
> > Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
> > ---
> >  target-s390x/cpu.c |   25 +++++++++++++++++++++++++
> >  target-s390x/kvm.c |   10 +++++++++-
> >  2 files changed, 34 insertions(+), 1 deletions(-)
> > 
> > diff --git a/target-s390x/cpu.c b/target-s390x/cpu.c
> > index 619b202..a601380 100644
> > --- a/target-s390x/cpu.c
> > +++ b/target-s390x/cpu.c
> > @@ -4,6 +4,7 @@
> >   * Copyright (c) 2009 Ulrich Hecht
> >   * Copyright (c) 2011 Alexander Graf
> >   * Copyright (c) 2012 SUSE LINUX Products GmbH
> > + * Copyright (c) 2012 IBM Corp.
> >   *
> >   * This library is free software; you can redistribute it and/or
> >   * modify it under the terms of the GNU Lesser General Public
> > @@ -18,12 +19,35 @@
> >   * 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/lgpl-2.1.html>
> > + * Contributions after 2012-12-07 are licensed under the terms of the
> > + * GNU GPL, version 2 or (at your option) any later version.
> > + *
> >   */
> >  
> >  #include "cpu.h"
> > +#include "hw/hw.h"
> >  #include "qemu-common.h"
> >  #include "qemu-timer.h"
> >  
> > +/* TODO: remove me, when reset over QOM tree is implemented */
> > +static void s390_cpu_machine_reset_cb(void *opaque)
> > +{
> > +    S390CPU *cpu = opaque;
> > +    CPUS390XState *env = &cpu->env;
> > +
> > +    memset(env->regs, 0, sizeof(env->regs));
> > +    memset(env->aregs, 0, sizeof(env->aregs));
> > +    memset(env->cregs, 0, sizeof(env->cregs));
> > +    memset(env->fregs, 0, sizeof(env->fregs));
> > +    /* architectured initial values for CR 0 and 14 */
> > +    env->cregs[0] = 0xE0UL;
> > +    env->cregs[14] = 0xC2000000UL;
> > +    env->psw.addr = 0;
> > +    /* set to z/Architecture mode */
> > +    env->psw.mask = 0x0000000180000000ULL;
> > +    env->psa = 0;
> > +    s390_del_running_cpu(env);
> > +}
> 
> What's the connection between lack of reset over QOM tree and not
> calling the existing s390_cpu_reset() from s390_cpu_machine_reset_cb()?
> Are some CPUS390XState fields maybe misplaced?

Thanks for the review!

Calling cpu_reset from s390_cpu_machine_reset() has an undesired
side-effect. By setting env->halted to zero we decrement our running cpu
counter too often. The way it is implemented in this patch, it works in all cases,
i.e. guest-triggered reboot, system_reset qmp command as well as system halt.

But I agree that it's not obvious why we do it this way. The running_cpus
counter complicates things. Maybe I can come up with a nicer solution...


Jens

> Regards,
> Andreas
> 
> >  
> >  /* CPUClass::reset() */
> >  static void s390_cpu_reset(CPUState *s)
> > @@ -56,6 +80,7 @@ static void s390_cpu_initfn(Object *obj)
> >  
> >      cpu_exec_init(env);
> >  #if !defined(CONFIG_USER_ONLY)
> > +    qemu_register_reset(s390_cpu_machine_reset_cb, cpu);
> >      qemu_get_timedate(&tm, 0);
> >      env->tod_offset = TOD_UNIX_EPOCH +
> >                        (time2tod(mktimegm(&tm)) * 1000000000ULL);
> > diff --git a/target-s390x/kvm.c b/target-s390x/kvm.c
> > index 94de764..3969a49 100644
> > --- a/target-s390x/kvm.c
> > +++ b/target-s390x/kvm.c
> > @@ -85,7 +85,15 @@ int kvm_arch_init_vcpu(CPUS390XState *env)
> >  
> >  void kvm_arch_reset_vcpu(CPUS390XState *env)
> >  {
> > -    /* FIXME: add code to reset vcpu. */
> > +    /* The initial reset call is needed here to reset in-kernel
> > +     * vcpu data that we can't access directly from QEMU
> > +     * (i.e. with older kernels which don't support sync_regs/ONE_REG).
> > +     * Before this ioctl cpu_synchronize_state() is called in common kvm
> > +     * code (kvm-all) */
> > +    if (kvm_vcpu_ioctl(env, KVM_S390_INITIAL_RESET, NULL)) {
> > +        perror("Can't reset vcpu\n");
> > +    }
> > +
> >  }
> >  
> >  int kvm_arch_put_registers(CPUS390XState *env, int level)
> > 
> 
> 
> -- 
> SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
> GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg
> 

-- 
Mit freundlichen Grüßen / Kind regards 

Jens Freimann 

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