Messages in this thread | | | Subject | Re: [PATCH v3 04/14] KVM: s390: device attribute to set AP interpretive execution | From | Pierre Morel <> | Date | Thu, 15 Mar 2018 17:00:03 +0100 |
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On 15/03/2018 16:23, Tony Krowiak wrote: > On 03/14/2018 05:57 PM, Halil Pasic wrote: >> >> On 03/14/2018 07:25 PM, Tony Krowiak wrote: >>> The VFIO AP device model exploits interpretive execution of AP >>> instructions (APIE) to provide guests passthrough access to AP >>> devices. This patch introduces a new device attribute in the >>> KVM_S390_VM_CRYPTO device attribute group to set APIE from >>> the VFIO AP device defined on the guest. >>> >>> Signed-off-by: Tony Krowiak <akrowiak@linux.vnet.ibm.com> >>> --- >> [..] >> >>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c >>> index a60c45b..bc46b67 100644 >>> --- a/arch/s390/kvm/kvm-s390.c >>> +++ b/arch/s390/kvm/kvm-s390.c >>> @@ -815,6 +815,19 @@ static int kvm_s390_vm_set_crypto(struct kvm >>> *kvm, struct kvm_device_attr *attr) >>> sizeof(kvm->arch.crypto.crycb->dea_wrapping_key_mask)); >>> VM_EVENT(kvm, 3, "%s", "DISABLE: DEA keywrapping support"); >>> break; >>> + case KVM_S390_VM_CRYPTO_INTERPRET_AP: >>> + if (attr->addr) { >>> + if (!test_kvm_cpu_feat(kvm, KVM_S390_VM_CPU_FEAT_AP)) >> Unlock mutex before returning? > The mutex is unlocked prior to return at the end of the function. >> >> Maybe flip conditions (don't allow manipulating apie if feature not >> there). >> Clearing the anyways clear apie if feature not there ain't too bad, but >> rejecting the operation appears nicer to me. > I think what you're saying is something like this: > > if (!test_kvm_cpu_feat(kvm, KVM_S390_VM_CPU_FEAT_AP)) > return -EOPNOTSUPP; > > kvm->arch.crypto.apie = (attr->addr) ? 1 : 0; > > I can make arguments for doing this either way, but since the attribute > is will most likely only be set by an AP device in userspace, I suppose > it makes sense to allow setting of the attribute if the AP feature is > installed. It certainly makes sense for the dedicated implementation. >> >>> + return -EOPNOTSUPP;
Obviously Halil is speaking on this return statement. Which returns without unlocking the mutex.
-- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany
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