Re: [PATCH v2 2/3] s390x: Add missing vcpu reset functions

[Cornelia Huck]

On Mon,  2 Dec 2019 09:01:45 -0500
Janosch Frank <address@hidden> wrote:

> Up to now we only had an ioctl to reset vcpu data QEMU couldn't reach
> for the initial reset, which was also called for the clear reset. To

s/which/and that/ ?

> 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 <address@hidden>
> ---
>  target/s390x/cpu.c       | 14 ++++++++++++--
>  target/s390x/kvm-stub.c  | 10 +++++++++-
>  target/s390x/kvm.c       | 42 ++++++++++++++++++++++++++++++++--------
>  target/s390x/kvm_s390x.h |  4 +++-
>  4 files changed, 58 insertions(+), 12 deletions(-)
> 
> diff --git a/target/s390x/cpu.c b/target/s390x/cpu.c
> index 829ce6ad54..906285888e 100644
> --- a/target/s390x/cpu.c
> +++ b/target/s390x/cpu.c
> @@ -139,8 +139,18 @@ static void s390_cpu_reset(CPUState *s, cpu_reset_type 
> type)
>      }
>  
>      /* Reset state inside the kernel that we cannot access yet from QEMU. */

Hm, why does this comment talk about 'yet'? Did we have any plans to
change that?

> -    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;

Add a default case to catch errors?

> +        }
>      }
>  }
>  

(...)

> diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
> index ad6e38c876..7a2ec8b9f8 100644
> --- a/target/s390x/kvm.c
> +++ b/target/s390x/kvm.c
> @@ -151,6 +151,7 @@ static int cap_s390_irq;
>  static int cap_ri;
>  static int cap_gs;
>  static int cap_hpage_1m;
> +static int cap_vcpu_resets;
>  
>  static int active_cmma;
>  
> @@ -342,6 +343,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
>      cap_async_pf = kvm_check_extension(s, KVM_CAP_ASYNC_PF);
>      cap_mem_op = kvm_check_extension(s, KVM_CAP_S390_MEM_OP);
>      cap_s390_irq = kvm_check_extension(s, KVM_CAP_S390_INJECT_IRQ);
> +    cap_vcpu_resets = kvm_check_extension(s, KVM_CAP_S390_VCPU_RESETS);
>  
>      if (!kvm_check_extension(s, KVM_CAP_S390_GMAP)
>          || !kvm_check_extension(s, KVM_CAP_S390_COW)) {
> @@ -403,20 +405,44 @@ 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

Is the reference to sync_regs/ONE_REG still relevant? I'm a bit
confused here, especially with regard to what we'll need for protected
virt.

> +     * 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", cs->cpu_index);
>      }
>  }
>  
> +void kvm_s390_reset_vcpu_initial(S390CPU *cpu)
> +{
> +    kvm_s390_reset_vcpu(cpu, KVM_S390_INITIAL_RESET);
> +}
> +
> +void kvm_s390_reset_vcpu_clear(S390CPU *cpu)
> +{
> +    if (!cap_vcpu_resets) {
> +        kvm_s390_reset_vcpu(cpu, KVM_S390_INITIAL_RESET);
> +    } else {
> +        kvm_s390_reset_vcpu(cpu, KVM_S390_CLEAR_RESET);
> +    }

kvm_s390_reset_vcpu(cpu, cap_vcpu_resets ? KVM_S390_CLEAR_RESET : 
KVM_S390_INITIAL_RESET);

One line, but maybe the conventional if is still better :)

> +}
> +
> +void kvm_s390_reset_vcpu_normal(S390CPU *cpu)
> +{
> +    if (!cap_vcpu_resets) {
> +        return;
> +    }
> +    kvm_s390_reset_vcpu(cpu, KVM_S390_NORMAL_RESET);
> +}
> +
>  static int can_sync_regs(CPUState *cs, int regs)
>  {
>      return cap_sync_regs && (cs->kvm_run->kvm_valid_regs & regs) == regs;
> diff --git a/target/s390x/kvm_s390x.h b/target/s390x/kvm_s390x.h
> index caf985955b..0b21789796 100644
> --- a/target/s390x/kvm_s390x.h
> +++ b/target/s390x/kvm_s390x.h
> @@ -34,7 +34,9 @@ int kvm_s390_assign_subch_ioeventfd(EventNotifier 
> *notifier, uint32_t sch,
>                                      int vq, bool assign);
>  int kvm_s390_cmma_active(void);
>  void kvm_s390_cmma_reset(void);
> -void kvm_s390_reset_vcpu(S390CPU *cpu);
> +void kvm_s390_reset_vcpu_clear(S390CPU *cpu);
> +void kvm_s390_reset_vcpu_normal(S390CPU *cpu);
> +void kvm_s390_reset_vcpu_initial(S390CPU *cpu);
>  int kvm_s390_set_mem_limit(uint64_t new_limit, uint64_t *hw_limit);
>  void kvm_s390_set_max_pagesize(uint64_t pagesize, Error **errp);
>  void kvm_s390_crypto_reset(void);