Messages in this thread | | | Subject | Re: [PATCH 1/2] s390/vfio-ap: r/w lock for PQAP interception handler function pointer | From | Christian Borntraeger <> | Date | Wed, 18 Aug 2021 19:03:33 +0200 |
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On 19.07.21 21:35, Tony Krowiak wrote: > The function pointer to the interception handler for the PQAP instruction > can get changed during the interception process. Let's add a > semaphore to struct kvm_s390_crypto to control read/write access to the > function pointer contained therein. > > The semaphore must be locked for write access by the vfio_ap device driver > when notified that the KVM pointer has been set or cleared. It must be > locked for read access by the interception framework when the PQAP > instruction is intercepted. > > Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com> > Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> > --- > arch/s390/include/asm/kvm_host.h | 8 +++----- > arch/s390/kvm/kvm-s390.c | 1 + > arch/s390/kvm/priv.c | 10 ++++++---- > drivers/s390/crypto/vfio_ap_ops.c | 23 +++++++++++++++++------ > drivers/s390/crypto/vfio_ap_private.h | 2 +- > 5 files changed, 28 insertions(+), 16 deletions(-) > > diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h > index 9b4473f76e56..f18849d259e6 100644 > --- a/arch/s390/include/asm/kvm_host.h > +++ b/arch/s390/include/asm/kvm_host.h > @@ -798,14 +798,12 @@ struct kvm_s390_cpu_model { > unsigned short ibc; > }; > > -struct kvm_s390_module_hook { > - int (*hook)(struct kvm_vcpu *vcpu); > - struct module *owner; > -}; > +typedef int (*crypto_hook)(struct kvm_vcpu *vcpu); > > struct kvm_s390_crypto { > struct kvm_s390_crypto_cb *crycb; > - struct kvm_s390_module_hook *pqap_hook; > + struct rw_semaphore pqap_hook_rwsem; > + crypto_hook *pqap_hook; > __u32 crycbd; > __u8 aes_kw; > __u8 dea_kw; > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c > index b655a7d82bf0..a08f242a9f27 100644 > --- a/arch/s390/kvm/kvm-s390.c > +++ b/arch/s390/kvm/kvm-s390.c > @@ -2630,6 +2630,7 @@ static void kvm_s390_crypto_init(struct kvm *kvm) > { > kvm->arch.crypto.crycb = &kvm->arch.sie_page2->crycb; > kvm_s390_set_crycb_format(kvm); > + init_rwsem(&kvm->arch.crypto.pqap_hook_rwsem); > > if (!test_kvm_facility(kvm, 76)) > return; > diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c > index 9928f785c677..6bed9406c1f3 100644 > --- a/arch/s390/kvm/priv.c > +++ b/arch/s390/kvm/priv.c > @@ -610,6 +610,7 @@ static int handle_io_inst(struct kvm_vcpu *vcpu) > static int handle_pqap(struct kvm_vcpu *vcpu) > { > struct ap_queue_status status = {}; > + crypto_hook pqap_hook; > unsigned long reg0; > int ret; > uint8_t fc; > @@ -657,15 +658,16 @@ static int handle_pqap(struct kvm_vcpu *vcpu) > * Verify that the hook callback is registered, lock the owner > * and call the hook. > */ > + down_read(&vcpu->kvm->arch.crypto.pqap_hook_rwsem); > if (vcpu->kvm->arch.crypto.pqap_hook) { > - if (!try_module_get(vcpu->kvm->arch.crypto.pqap_hook->owner)) > - return -EOPNOTSUPP; > - ret = vcpu->kvm->arch.crypto.pqap_hook->hook(vcpu); > - module_put(vcpu->kvm->arch.crypto.pqap_hook->owner); > + pqap_hook = *vcpu->kvm->arch.crypto.pqap_hook;
Dont we have to check for NULL here? If not can you add a comment why?
Otherwise this looks good.
> + ret = pqap_hook(vcpu); [...]
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