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

Christian Borntraeger
2018-09-24T10:32:09Z

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.

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);
>