Re: [Qemu-devel] [PATCH 2/3] s390: Add CPU reset handler

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

On Thu, Jan 03, 2013 at 01:50:22PM +0100, Alexander Graf wrote:
> 
> On 18.12.2012, at 18:50, Jens Freimann wrote:
> 
> > Add a CPU reset handler to have all CPUs in a PoP compliant
> > state.
> > 
> > Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
> > 
> > ---
> > v2 -> v3:
> > * remove FIXME
> > * separate parent reset from local reset by adding a while line
> > * use defines for register reset values
> > 
> > v1 -> v2:
> > * move setting of control registers and psa to s390_cpu_reset
> >  and call it from the new s390_machine_cpu_reset_cb()
> >  This makes it more similar to how it is done on x86
> > * in s390_cpu_reset() set env->halted state of cpu after
> >  the memset. This is needed to keep our s390_cpu_running
> >  counter in sync when s390_cpu_reset is called via the
> >  qemu_devices_reset path
> > * set env->halted state in s390_cpu_initfn to 1 to avoid
> >  decrementing the cpu counter during first reset
> > ---
> > target-s390x/cpu.c | 35 +++++++++++++++++++++++++++++++++--
> > target-s390x/kvm.c |  9 ++++++++-
> > 2 files changed, 41 insertions(+), 3 deletions(-)
> > 
> > diff --git a/target-s390x/cpu.c b/target-s390x/cpu.c
> > index 619b202..58e412a 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 +19,19 @@
> >  * 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 2012-12-11 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"
> > 
> > +#define IPL_PSW_MASK    0x0000000180000000ULL
> > +#define CR0_RESET       0xE0UL
> > +#define CR14_RESET      0xC2000000UL;
> > 
> > /* CPUClass::reset() */
> > static void s390_cpu_reset(CPUState *s)
> > @@ -37,12 +45,30 @@ static void s390_cpu_reset(CPUState *s)
> >         log_cpu_state(env, 0);
> >     }
> > 
> > +    s390_del_running_cpu(env);
> > +
> >     scc->parent_reset(s);
> > 
> >     memset(env, 0, offsetof(CPUS390XState, breakpoints));
> > -    /* FIXME: reset vector? */
> > +
> > +    /* architectured initial values for CR 0 and 14 */
> > +    env->cregs[0] = CR0_RESET;
> > +    env->cregs[14] = CR14_RESET;
> > +    /* set to z/Architecture mode */
> > +    env->psw.mask = IPL_PSW_MASK;
> 
> Why would we set psw.mask, but not psw.addr? In fact, why are we setting psw at all here? Shouldn't we just leave it at 0 from the memset and simply override it in the ipl device?

I agree that it's redundand as we set it in the ipl device code and that it would work without setting
the mask here. I put it in here because I consider it part of the CPU reset code since we always want to start
in z/Architecture mode regardless of what code runs after the reset.

Jens

> 
> Alex
>