Re: [PATCH v10 01/26] KVM: s390: vsie: simulate VCPU SIE entry/exit

[Tony Krowiak <akrowiak@linux.ibm.com>]

On 09/24/2018 06:32 AM, Christian Borntraeger wrote:
> 
> 
> On 09/12/2018 09:42 PM, Tony Krowiak wrote:
>> From: David Hildenbrand <david@redhat.com>
>>
>> VCPU requests and VCPU blocking right now don't take care of the vSIE
>> (as it was not necessary until now). But we want to have synchronous VCPU
>> requests that will also be handled before running the vSIE again.
>>
>> So let's simulate a SIE entry of the VCPU when calling the sie during
>> vSIE handling and check for PROG_ flags. The existing infrastructure
>> (e.g. exit_sie()) will then detect that the SIE (in form of the vSIE) is
>> running and properly kick the vSIE CPU, resulting in it leaving the vSIE
>> loop and therefore the vSIE interception handler, allowing it to handle
>> VCPU requests.
>>
>> E.g. if we want to modify the crycb of the VCPU and make sure that any
>> masks also get applied to the VSIE crycb shadow (which uses masks from the
>> VCPU crycb), we will need a way to hinder the vSIE from running and make
>> sure to process the updated crycb before reentering the vSIE again.
>>
>> Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
>> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
>> Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
>> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
> 
> I guess you should want to swap both signoffs? In the end they should show the
> patch flow.

Will do.

> 
> Other than that:
> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
> 
> 
>> ---
>>   arch/s390/kvm/kvm-s390.c |    9 ++++++++-
>>   arch/s390/kvm/kvm-s390.h |    1 +
>>   arch/s390/kvm/vsie.c     |   21 +++++++++++++++++----
>>   3 files changed, 26 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>> index f69333f..0b5aff0 100644
>> --- a/arch/s390/kvm/kvm-s390.c
>> +++ b/arch/s390/kvm/kvm-s390.c
>> @@ -2768,18 +2768,25 @@ static void kvm_s390_vcpu_request(struct kvm_vcpu *vcpu)
>>   	exit_sie(vcpu);
>>   }
>>
>> +bool kvm_s390_vcpu_sie_inhibited(struct kvm_vcpu *vcpu)
>> +{
>> +	return atomic_read(&vcpu->arch.sie_block->prog20) &
>> +	       (PROG_BLOCK_SIE | PROG_REQUEST);
>> +}
>> +
>>   static void kvm_s390_vcpu_request_handled(struct kvm_vcpu *vcpu)
>>   {
>>   	atomic_andnot(PROG_REQUEST, &vcpu->arch.sie_block->prog20);
>>   }
>>
>>   /*
>> - * Kick a guest cpu out of SIE and wait until SIE is not running.
>> + * Kick a guest cpu out of (v)SIE and wait until (v)SIE is not running.
>>    * If the CPU is not running (e.g. waiting as idle) the function will
>>    * return immediately. */
>>   void exit_sie(struct kvm_vcpu *vcpu)
>>   {
>>   	kvm_s390_set_cpuflags(vcpu, CPUSTAT_STOP_INT);
>> +	kvm_s390_vsie_kick(vcpu);
>>   	while (vcpu->arch.sie_block->prog0c & PROG_IN_SIE)
>>   		cpu_relax();
>>   }
>> diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
>> index 981e3ba..1f6e36c 100644
>> --- a/arch/s390/kvm/kvm-s390.h
>> +++ b/arch/s390/kvm/kvm-s390.h
>> @@ -290,6 +290,7 @@ void kvm_s390_set_tod_clock(struct kvm *kvm,
>>   void kvm_s390_vcpu_stop(struct kvm_vcpu *vcpu);
>>   void kvm_s390_vcpu_block(struct kvm_vcpu *vcpu);
>>   void kvm_s390_vcpu_unblock(struct kvm_vcpu *vcpu);
>> +bool kvm_s390_vcpu_sie_inhibited(struct kvm_vcpu *vcpu);
>>   void exit_sie(struct kvm_vcpu *vcpu);
>>   void kvm_s390_sync_request(int req, struct kvm_vcpu *vcpu);
>>   int kvm_s390_vcpu_setup_cmma(struct kvm_vcpu *vcpu);
>> diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
>> index a2b28cd..12b9707 100644
>> --- a/arch/s390/kvm/vsie.c
>> +++ b/arch/s390/kvm/vsie.c
>> @@ -830,7 +830,7 @@ static int do_vsie_run(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>>   	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
>>   	struct kvm_s390_sie_block *scb_o = vsie_page->scb_o;
>>   	int guest_bp_isolation;
>> -	int rc;
>> +	int rc = 0;
>>
>>   	handle_last_fault(vcpu, vsie_page);
>>
>> @@ -858,7 +858,18 @@ static int do_vsie_run(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>>   	guest_enter_irqoff();
>>   	local_irq_enable();
>>
>> -	rc = sie64a(scb_s, vcpu->run->s.regs.gprs);
>> +	/*
>> +	 * Simulate a SIE entry of the VCPU (see sie64a), so VCPU blocking
>> +	 * and VCPU requests also hinder the vSIE from running and lead
>> +	 * to an immediate exit. kvm_s390_vsie_kick() has to be used to
>> +	 * also kick the vSIE.
>> +	 */
>> +	vcpu->arch.sie_block->prog0c |= PROG_IN_SIE;
>> +	barrier();
>> +	if (!kvm_s390_vcpu_sie_inhibited(vcpu))
>> +		rc = sie64a(scb_s, vcpu->run->s.regs.gprs);
>> +	barrier();
>> +	vcpu->arch.sie_block->prog0c &= ~PROG_IN_SIE;
>>
>>   	local_irq_disable();
>>   	guest_exit_irqoff();
>> @@ -1005,7 +1016,8 @@ static int vsie_run(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>>   		if (rc == -EAGAIN)
>>   			rc = 0;
>>   		if (rc || scb_s->icptcode || signal_pending(current) ||
>> -		    kvm_s390_vcpu_has_irq(vcpu, 0))
>> +		    kvm_s390_vcpu_has_irq(vcpu, 0) ||
>> +		    kvm_s390_vcpu_sie_inhibited(vcpu))
>>   			break;
>>   	}
>>
>> @@ -1122,7 +1134,8 @@ int kvm_s390_handle_vsie(struct kvm_vcpu *vcpu)
>>   	if (unlikely(scb_addr & 0x1ffUL))
>>   		return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
>>
>> -	if (signal_pending(current) || kvm_s390_vcpu_has_irq(vcpu, 0))
>> +	if (signal_pending(current) || kvm_s390_vcpu_has_irq(vcpu, 0) ||
>> +	    kvm_s390_vcpu_sie_inhibited(vcpu))
>>   		return 0;
>>
>>   	vsie_page = get_vsie_page(vcpu->kvm, scb_addr);
>>