Messages in this thread | | | Date | Mon, 7 Feb 2022 12:04:56 +0100 | From | Janosch Frank <> | Subject | Re: [PATCH v7 10/17] KVM: s390: pv: add mmu_notifier |
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On 2/4/22 16:53, Claudio Imbrenda wrote: > Add an mmu_notifier for protected VMs. The callback function is > triggered when the mm is torn down, and will attempt to convert all > protected vCPUs to non-protected. This allows the mm teardown to use > the destroy page UVC instead of export. > > Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com> > --- > arch/s390/include/asm/kvm_host.h | 2 ++ > arch/s390/kvm/pv.c | 20 ++++++++++++++++++++ > 2 files changed, 22 insertions(+) > > diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h > index a22c9266ea05..1bccb8561ba9 100644 > --- a/arch/s390/include/asm/kvm_host.h > +++ b/arch/s390/include/asm/kvm_host.h > @@ -19,6 +19,7 @@ > #include <linux/kvm.h> > #include <linux/seqlock.h> > #include <linux/module.h> > +#include <linux/mmu_notifier.h> > #include <asm/debug.h> > #include <asm/cpu.h> > #include <asm/fpu/api.h> > @@ -921,6 +922,7 @@ struct kvm_s390_pv { > u64 guest_len; > unsigned long stor_base; > void *stor_var; > + struct mmu_notifier mmu_notifier; > }; > > struct kvm_arch{ > diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c > index f1e812a45acb..d3b8fd9b5b3e 100644 > --- a/arch/s390/kvm/pv.c > +++ b/arch/s390/kvm/pv.c > @@ -193,6 +193,21 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc) > return -EIO; > } > > +static void kvm_s390_pv_mmu_notifier_release(struct mmu_notifier *subscription, > + struct mm_struct *mm) > +{ > + struct kvm *kvm = container_of(subscription, struct kvm, arch.pv.mmu_notifier);
Are we sure that the kvm pointer is still valid at this point?
> + u16 dummy; > + > + mutex_lock(&kvm->lock);
Against what are we locking here?
> + kvm_s390_cpus_from_pv(kvm, &dummy, &dummy);
I'd guess that we can't really have a second kvm_s390_cpus_from_pv() call in flight, right? If the mm is being torn down there would be no code left that can execute the IOCTL.
> + mutex_unlock(&kvm->lock); > +} > + > +static const struct mmu_notifier_ops kvm_s390_pv_mmu_notifier_ops = { > + .release = kvm_s390_pv_mmu_notifier_release, > +}; > + > int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc) > { > struct uv_cb_cgc uvcb = { > @@ -234,6 +249,11 @@ int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc) > return -EIO; > } > kvm->arch.gmap->guest_handle = uvcb.guest_handle; > + /* Add the notifier only once. No races because we hold kvm->lock */ > + if (kvm->arch.pv.mmu_notifier.ops != &kvm_s390_pv_mmu_notifier_ops) { > + kvm->arch.pv.mmu_notifier.ops = &kvm_s390_pv_mmu_notifier_ops; > + mmu_notifier_register(&kvm->arch.pv.mmu_notifier, kvm->mm); > + } > return 0; > } > >
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