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

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Message-Id: <0ade216d-b206-abe3-418c-199d9278e37e@de.ibm.com>
Date:   Mon, 24 Sep 2018 12:32:09 +0200
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Tony Krowiak <akrowiak@...ux.vnet.ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     freude@...ibm.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, cohuck@...hat.com, kwankhede@...dia.com,
        bjsdjshi@...ux.vnet.ibm.com, pbonzini@...hat.com,
        alex.williamson@...hat.com, pmorel@...ux.vnet.ibm.com,
        alifm@...ux.vnet.ibm.com, mjrosato@...ux.vnet.ibm.com,
        jjherne@...ux.vnet.ibm.com, thuth@...hat.com,
        pasic@...ux.vnet.ibm.com, berrange@...hat.com,
        fiuczy@...ux.vnet.ibm.com, buendgen@...ibm.com,
        frankja@...ux.ibm.com, David Hildenbrand <david@...hat.com>,
        Tony Krowiak <akrowiak@...ux.ibm.com>
Subject: Re: [PATCH v10 01/26] KVM: s390: vsie: simulate VCPU SIE entry/exit



On 09/12/2018 09:42 PM, Tony Krowiak wrote:
> From: David Hildenbrand <david@...hat.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@...ux.ibm.com>
> Reviewed-by: Cornelia Huck <cohuck@...hat.com>
> Reviewed-by: Janosch Frank <frankja@...ux.ibm.com>
> Signed-off-by: Tony Krowiak <akrowiak@...ux.ibm.com>
> Signed-off-by: David Hildenbrand <david@...hat.com>

I guess you should want to swap both signoffs? In the end they should show the
patch flow. 

Other than that:
Reviewed-by: Christian Borntraeger <borntraeger@...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);
>