Re: [PATCH v2] KVM: s390: Also reset registers in sync regs for initial cpu reset

[Christian Borntraeger <borntraeger@de.ibm.com>]

On 10.03.20 14:21, David Hildenbrand wrote:
> On 10.03.20 14:12, Christian Borntraeger wrote:
>> When we do the initial CPU reset we must not only clear the registers
>> in the internal data structures but also in kvm_run sync_regs. For
>> modern userspace sync_regs is the only place that it looks at.
>>
>> Cc: stable@vger.kernel.org
> 
> # v?
> 
>> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
>> ---
>>  arch/s390/kvm/kvm-s390.c | 18 +++++++++++++++++-
>>  1 file changed, 17 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>> index d7ff30e45589..c2e6d4ba4e23 100644
>> --- a/arch/s390/kvm/kvm-s390.c
>> +++ b/arch/s390/kvm/kvm-s390.c
>> @@ -3268,7 +3268,10 @@ static void kvm_arch_vcpu_ioctl_initial_reset(struct kvm_vcpu *vcpu)
>>  	/* Initial reset is a superset of the normal reset */
>>  	kvm_arch_vcpu_ioctl_normal_reset(vcpu);
>>  
>> -	/* this equals initial cpu reset in pop, but we don't switch to ESA */
>> +	/*
>> +	 * This equals initial cpu reset in pop, but we don't switch to ESA.
>> +	 * We do not only reset the internal data, but also ...
>> +	 */
>>  	vcpu->arch.sie_block->gpsw.mask = 0;
>>  	vcpu->arch.sie_block->gpsw.addr = 0;
>>  	kvm_s390_set_prefix(vcpu, 0);
>> @@ -3278,6 +3281,19 @@ static void kvm_arch_vcpu_ioctl_initial_reset(struct kvm_vcpu *vcpu)
>>  	memset(vcpu->arch.sie_block->gcr, 0, sizeof(vcpu->arch.sie_block->gcr));
>>  	vcpu->arch.sie_block->gcr[0] = CR0_INITIAL_MASK;
>>  	vcpu->arch.sie_block->gcr[14] = CR14_INITIAL_MASK;
>> +
>> +	/* ... the data in sync regs */
>> +	memset(vcpu->run->s.regs.crs, 0, sizeof(vcpu->run->s.regs.crs));
>> +	vcpu->run->s.regs.ckc = 0;
>> +	vcpu->run->s.regs.crs[0] = CR0_INITIAL_MASK;
>> +	vcpu->run->s.regs.crs[14] = CR14_INITIAL_MASK;
>> +	vcpu->run->psw_addr = 0;
>> +	vcpu->run->psw_mask = 0;
>> +	vcpu->run->s.regs.todpr = 0;
>> +	vcpu->run->s.regs.cputm = 0;
>> +	vcpu->run->s.regs.ckc = 0;
>> +	vcpu->run->s.regs.pp = 0;
>> +	vcpu->run->s.regs.gbea = 1;
>>  	vcpu->run->s.regs.fpc = 0;
>>  	vcpu->arch.sie_block->gbea = 1;
>>  	vcpu->arch.sie_block->pp = 0;
>>
> 
> Acked-by: David Hildenbrand <david@redhat.com>
> 
> However, I do wonder if that ioctl *originally* was designed for that -
> IOW if this is rally a stable patch or just some change that makes
> sense. IIRC, userspace/QEMU always did the right thing, no? There was no
> documentation about the guarantees AFAIK.
> 

Yes, I moved forth and back. 
Maybe removing cc stable and just adding
Fixes: 7de3f1423ff ("KVM: s390: Add new reset vcpu API")
is better then.