Re: [PATCH v3 2/4] s390x: Add missing vcpu reset functions

[Cornelia Huck <cohuck@redhat.com>]

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On Wed, 4 Dec 2019 10:00:45 +0100
Janosch Frank <frankja@linux.ibm.com> wrote:

> On 12/3/19 6:44 PM, Cornelia Huck wrote:
> > On Tue,  3 Dec 2019 08:28:11 -0500
> > Janosch Frank <frankja@linux.ibm.com> wrote:
> >   
> >> Up to now we only had an ioctl to reset vcpu data QEMU couldn't reach
> >> for the initial reset, and that was also called for the clear
> >> reset. To be architecture compliant, we also need to clear local
> >> interrupts on a normal reset.
> >>
> >> Because of this and the upcoming protvirt support we need to add
> >> ioctls for the missing clear and normal resets.
> >>
> >> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> >> Reviewed-by: Thomas Huth <thuth@redhat.com>
> >> Acked-by: David Hildenbrand <david@redhat.com>
> >> ---
> >>  target/s390x/cpu.c       | 16 +++++++++++++--
> >>  target/s390x/kvm-stub.c  | 10 +++++++++-
> >>  target/s390x/kvm.c       | 42 ++++++++++++++++++++++++++++++++--------
> >>  target/s390x/kvm_s390x.h |  4 +++-
> >>  4 files changed, 60 insertions(+), 12 deletions(-)
> >>
> >> diff --git a/target/s390x/cpu.c b/target/s390x/cpu.c
> >> index 829ce6ad54..4973365d6c 100644
> >> --- a/target/s390x/cpu.c
> >> +++ b/target/s390x/cpu.c
> >> @@ -139,8 +139,20 @@ static void s390_cpu_reset(CPUState *s, cpu_reset_type type)
> >>      }
> >>  
> >>      /* Reset state inside the kernel that we cannot access yet from QEMU. */  
> > 
> > For the last iteration, I asked about the 'yet' here...  
> 
> I have not written those comments, I merely refuse to delete them :)
> We still reset some state in the kernel, I'm not sure how much of that
> is already exposed via ioctls to QEMU, so I won't remove the comment.
> 
> >   
> >> -    if (kvm_enabled() && type != S390_CPU_RESET_NORMAL) {
> >> -        kvm_s390_reset_vcpu(cpu);
> >> +    if (kvm_enabled()) {
> >> +        switch (type) {
> >> +        case S390_CPU_RESET_CLEAR:
> >> +            kvm_s390_reset_vcpu_clear(cpu);
> >> +            break;
> >> +        case S390_CPU_RESET_INITIAL:
> >> +            kvm_s390_reset_vcpu_initial(cpu);
> >> +            break;
> >> +        case S390_CPU_RESET_NORMAL:
> >> +            kvm_s390_reset_vcpu_normal(cpu);
> >> +            break;
> >> +        default:
> >> +            g_assert_not_reached();
> >> +        }
> >>      }
> >>  }
> >>    
> > 
> > (...)
> >   
> >> @@ -403,17 +405,41 @@ int kvm_arch_destroy_vcpu(CPUState *cs)
> >>      return 0;
> >>  }
> >>  
> >> -void kvm_s390_reset_vcpu(S390CPU *cpu)
> >> +static void kvm_s390_reset_vcpu(S390CPU *cpu, unsigned long type)
> >>  {
> >>      CPUState *cs = CPU(cpu);
> >>  
> >> -    /* 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(cs, KVM_S390_INITIAL_RESET, NULL)) {
> >> -        error_report("Initial CPU reset failed on CPU %i", cs->cpu_index);
> >> +    /*
> >> +     * The 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  
> > 
> > ...and this reference to 'older kernels' here.
> > 
> > Are the comments still correct/relevant?  
> 
> See above

Fair enough, let's keep them for now and revisit this later.

> 
> >   
> >> +     * cpu_synchronize_state() is called in common kvm code
> >> +     * (kvm-all).
> >> +     */
> >> +    if (kvm_vcpu_ioctl(cs, type)) {
> >> +        error_report("CPU reset failed on CPU %i type %lx",
> >> +                     cs->cpu_index, type);
> >> +    }
> >> +}  
> >   
> 
> 


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