Re: [Qemu-devel] [PATCH v2] s390: clear registers, psw and prefix at vcpu reset

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

On Tue, Nov 27, 2012 at 10:37:25AM +0100, Alexander Graf wrote:
> 
> 
> On 27.11.2012, at 09:33, Jens Freimann <jfrei@linux.vnet.ibm.com> wrote:
> 
> > When resetting vcpus on s390/kvm we have to clear registers, psw
> > and prefix as described in the z/Architecture PoP, otherwise a
> > reboot won't work. IPL PSW and prefix are set later on by the
> > s390-ipl device reset code.
> > 
> > Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
> > ---
> > 
> > changes v1->v2:
> > - moved cpu reset code from kvm.c to cpu.c
> > - only kvm initial_reset ioctl remains in kvm.c
> > - registered reset handler for s390 cpu reset, like x86 does it
> > 
> > target-s390x/cpu.c | 29 +++++++++++++++++++++++++++--
> > target-s390x/kvm.c |  9 ++++++++-
> > 2 files changed, 35 insertions(+), 3 deletions(-)
> > 
> > diff --git a/target-s390x/cpu.c b/target-s390x/cpu.c
> > index 619b202..f74d6f6 100644
> > --- a/target-s390x/cpu.c
> > +++ b/target-s390x/cpu.c
> > @@ -24,10 +24,21 @@
> > #include "qemu-common.h"
> > #include "qemu-timer.h"
> > 
> > +#ifndef CONFIG_USER_ONLY
> > +#include "hw/s390x/sclp.h"
> > +
> > +/* TODO: remove me, when reset over QOM tree is implemented */
> > +static void s390_cpu_machine_reset_cb(void *opaque)
> > +{
> > +    S390CPU *cpu = opaque;
> > +    cpu_reset(CPU(cpu));
> > +}
> > +#endif
> > 
> > /* CPUClass::reset() */
> > static void s390_cpu_reset(CPUState *s)
> > {
> > +    int i;
> >     S390CPU *cpu = S390_CPU(s);
> >     S390CPUClass *scc = S390_CPU_GET_CLASS(cpu);
> >     CPUS390XState *env = &cpu->env;
> > @@ -40,9 +51,22 @@ static void s390_cpu_reset(CPUState *s)
> >     scc->parent_reset(s);
> > 
> >     memset(env, 0, offsetof(CPUS390XState, breakpoints));
> > -    /* FIXME: reset vector? */
> > +
> > +    env->halted = 1;
> 
> Every cpu would start in halted state? So how does the primary one get rolling?

The first cpu is set to not-halted by the ipl device reset code.
> 
> > +    env->exception_index = EXCP_HLT;
> > +    for (i = 0; i < 16; i++) {
> > +        env->regs[i] = 0;
> > +        env->aregs[i] = 0;
> > +        env->cregs[i] = 0;
> > +        env->fregs[i].ll = 0;
> > +    }
> 
> Please make this more self-adjusting. For example using memset(sizeof));. You could also make the clear implicit by ensuring the registers are in the cpu struct before breakpoints. But explicit tends to be more readable ;).

Ok

> > +    /* architectured initial values for CR 0 and 14 */
> > +    env->cregs[0] = 0xE0UL;
> > +    env->cregs[14] = 0xC2000000UL;
> > +    env->psw.mask = 0;
> > +    env->psw.addr = 0;
> > +    env->psa = 0;
> >     tlb_flush(env, 1);
> > -    s390_add_running_cpu(env);
> 
> Why can we remove this one?

Good point. I took a closer look and found that we add an additional
cpu to the counter every time we reboot. Will fix this and send a new
version.

Jens

> 
> Alex
> 
> > }
> > 
> > static void s390_cpu_initfn(Object *obj)
> > @@ -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..d26555f 100644
> > --- a/target-s390x/kvm.c
> > +++ b/target-s390x/kvm.c
> > @@ -85,7 +85,14 @@ 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)
> > -- 
> > 1.7.12.4
> > 
> 

-- 
Mit freundlichen Grüßen / Kind regards 

Jens Freimann 

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