On 07.08.2018 14:51, David Hildenbrand wrote: > 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 VCPU requests > that will also be handled before running the vSIE again. > > So let's simulate a SIE entry when entering the vSIE loop and check > for PROG_ flags. The existing infrastructure (e.g. exit_sie()) will then > detect that the SIE (in form of the vSIE execution loop) 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. > > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> > --- > arch/s390/kvm/kvm-s390.c | 9 ++++++++- > arch/s390/kvm/kvm-s390.h | 1 + > arch/s390/kvm/vsie.c | 20 ++++++++++++++++++-- > 3 files changed, 27 insertions(+), 3 deletions(-) > > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c > index 91ad4a9425c0..c87734a31fdb 100644 > --- a/arch/s390/kvm/kvm-s390.c > +++ b/arch/s390/kvm/kvm-s390.c > @@ -2766,18 +2766,25 @@ 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 981e3ba97461..1f6e36cdce0d 100644 > --- a/arch/s390/kvm/kvm-s390.h > +++ b/arch/s390/kvm/kvm-s390.h > @@ -290,6 +290,7 @@ void kvm_s390_vcpu_start(struct kvm_vcpu *vcpu); > 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 63844b95c22c..faac06886f77 100644 > --- a/arch/s390/kvm/vsie.c > +++ b/arch/s390/kvm/vsie.c > @@ -989,6 +989,17 @@ static int vsie_run(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page) > struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s; > int rc = 0; > > + /* > + * Simulate a SIE entry of the VCPU (see sie64a), so VCPU blocking > + * and VCPU requests can hinder the whole vSIE loop from running > + * and lead to an immediate exit. We do it at this point (not > + * earlier), so kvm_s390_vsie_kick() works correctly already. > + */ > + vcpu->arch.sie_block->prog0c |= PROG_IN_SIE; > + barrier(); > + if (kvm_s390_vcpu_sie_inhibited(vcpu)) > + return 0; > + > while (1) { > rc = acquire_gmap_shadow(vcpu, vsie_page); > if (!rc) > @@ -1004,10 +1015,14 @@ 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; > } > > + barrier(); > + vcpu->arch.sie_block->prog0c &= ~PROG_IN_SIE; > + I am thinking about moving this down to the actual sie64 call. We eventually take locks and even call into MM code (to resolve faults) inside do_vsie_run(). I think this extra overhead can be avoided (where any caller - e.g. on prefix unmaps has to wait). -- Thanks, David / dhildenb -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html