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

[Janosch Frank]

On 12/2/19 4:46 PM, Cornelia Huck wrote:
> 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/ ?

Ok

> 
>> 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?

You're asking the wrong person :)

> 
>> -    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?

Sure, just did

> 
>> +        }
>>      }
>>  }
>>  
> 
> (...)
> 
>> 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.

I just didn't want to move/remove stuff
Even with kvm_run we do a lot of stuff for the initial reset.

> 
>> +     * 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 :)

I'd like to keep it as is.

> 
>> +}
>> +
>> +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);
> 
>

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