Messages in this thread | | | Subject | Re: [PATCH] KVM: s390: reset crypto attributes for all vcpus | From | Tony Krowiak <> | Date | Sun, 22 Apr 2018 11:06:43 -0400 |
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On 04/20/2018 08:26 AM, David Hildenbrand wrote: > On 19.04.2018 23:13, Tony Krowiak wrote: >> Introduces a new function to reset the crypto attributes for all >> vcpus whether they are running or not. Each vcpu in KVM will >> be removed from SIE prior to resetting the crypto attributes in its >> SIE state description. After all vcpus have had their crypto attributes >> reset the vcpus will be restored to SIE. >> >> This function is incorporated into the kvm_s390_vm_set_crypto(kvm) >> function to fix a reported issue whereby the crypto key wrapping >> attributes could potentially get out of synch for running vcpus. >> >> Reported-by: Halil Pasic <pasic@linux.vnet.ibm.com> > A reported-by for a code refactoring is strange.
I was asked to include this.
> >> Signed-off-by: Tony Krowiak <akrowiak@linux.vnet.ibm.com> >> --- >> arch/s390/kvm/kvm-s390.c | 18 ++++++++++++++---- >> arch/s390/kvm/kvm-s390.h | 13 +++++++++++++ >> 2 files changed, 27 insertions(+), 4 deletions(-) >> >> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c >> index fa355a6..4fa3037 100644 >> --- a/arch/s390/kvm/kvm-s390.c >> +++ b/arch/s390/kvm/kvm-s390.c >> @@ -789,6 +789,19 @@ static int kvm_s390_set_mem_control(struct kvm *kvm, struct kvm_device_attr *att >> return ret; >> } >> >> +void kvm_s390_vcpu_crypto_reset_all(struct kvm *kvm) >> + { >> + int i; >> + struct kvm_vcpu *vcpu; >> + >> + kvm_s390_vcpu_block_all(kvm); >> + >> + kvm_for_each_vcpu(i, vcpu, kvm) >> + kvm_s390_vcpu_crypto_setup(vcpu); >> + >> + kvm_s390_vcpu_unblock_all(kvm); > This code has to be protected by kvm->lock. Can that be guaranteed by > the caller?
I can hold the kvm->lock in this function, but if you look at the function from which it is called, kvm_s390_vm_set_crypto(vcpu) below, the kvm->lock is already held by that function to do other work. I suppose the kvm_s390_vm_set_crypto(vcpu) instruction could have released the lock prior to calling kvm_s390_vcpu_crypto_reset_all(kvm), but since this function is called within a block of crypto work, it made sense to me to place the responsibility for locking in the caller and include a comment in the comments for the function definition:
Note: The kvm->lock must be held while calling this function
> >> +} >> + >> static void kvm_s390_vcpu_crypto_setup(struct kvm_vcpu *vcpu); >> >> static int kvm_s390_vm_set_crypto(struct kvm *kvm, struct kvm_device_attr *attr) >> @@ -832,10 +845,7 @@ static int kvm_s390_vm_set_crypto(struct kvm *kvm, struct kvm_device_attr *attr) >> return -ENXIO; >> } >> >> - kvm_for_each_vcpu(i, vcpu, kvm) { >> - kvm_s390_vcpu_crypto_setup(vcpu); >> - exit_sie(vcpu); >> - } >> + kvm_s390_vcpu_crypto_reset_all(kvm); >> mutex_unlock(&kvm->lock); >> return 0; >> } >> diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h >> index 1b5621f..981e3ba 100644 >> --- a/arch/s390/kvm/kvm-s390.h >> +++ b/arch/s390/kvm/kvm-s390.h >> @@ -410,4 +410,17 @@ static inline int kvm_s390_use_sca_entries(void) >> } >> void kvm_s390_reinject_machine_check(struct kvm_vcpu *vcpu, >> struct mcck_volatile_info *mcck_info); >> + >> +/** >> + * kvm_s390_vcpu_crypto_reset_all >> + * >> + * Reset the crypto attributes for each vcpu. This can be done while the vcpus >> + * are running as each vcpu will be removed from SIE before resetting the crypt >> + * attributes and restored to SIE afterward. >> + * >> + * Note: The kvm->lock must be held while calling this function >> + * >> + * @kvm: the KVM guest >> + */ >> +void kvm_s390_vcpu_crypto_reset_all(struct kvm *kvm); >> #endif >> >
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