Re: [PATCH v9 13/18] KVM: s390: pv: cleanup leftover protected VMs if needed

Claudio Imbrenda
2022-04-01T15:52:07Z

On Thu, 31 Mar 2022 16:02:55 +0200
Janosch Frank <frankja@linux.ibm.com> wrote:

> On 3/30/22 14:26, Claudio Imbrenda wrote:
> > In upcoming patches it will be possible to start tearing down a
> > protected VM, and finish the teardown concurrently in a different
> > thread.
> >
> > Protected VMs that are pending for tear down ("leftover") need to be
> > cleaned properly when the userspace process (e.g. qemu) terminates.
> >
> > This patch makes sure that all "leftover" protected VMs are always
> > properly torn down.
> >
> > Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> > ---
> > arch/s390/include/asm/kvm_host.h | 2 +
> > arch/s390/kvm/kvm-s390.c | 1 +
> > arch/s390/kvm/pv.c | 69 ++++++++++++++++++++++++++++++++
> > 3 files changed, 72 insertions(+)
> >
> > diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> > index 1bccb8561ba9..50e3516cbc03 100644
> > --- a/arch/s390/include/asm/kvm_host.h
> > +++ b/arch/s390/include/asm/kvm_host.h
> > @@ -922,6 +922,8 @@ struct kvm_s390_pv {
> > u64 guest_len;
> > unsigned long stor_base;
> > void *stor_var;
> > + void *async_deinit;
> > + struct list_head need_cleanup;
> > struct mmu_notifier mmu_notifier;
> > };
> >
> > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> > index 446f89db93a1..3637f556ff33 100644
> > --- a/arch/s390/kvm/kvm-s390.c
> > +++ b/arch/s390/kvm/kvm-s390.c
> > @@ -2788,6 +2788,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> > kvm_s390_vsie_init(kvm);
> > if (use_gisa)
> > kvm_s390_gisa_init(kvm);
> > + INIT_LIST_HEAD(&kvm->arch.pv.need_cleanup);
>
> kvm->arch.pv.sync_deinit = NULL;

isn't the struct allocated with __GFP_ZERO ?

>
> > KVM_EVENT(3, "vm 0x%pK created by pid %u", kvm, current->pid);
> >
> > return 0;
> > diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
> > index be3b467f8feb..56412617dd01 100644
> > --- a/arch/s390/kvm/pv.c
> > +++ b/arch/s390/kvm/pv.c
> > @@ -17,6 +17,19 @@
> > #include <linux/mmu_notifier.h>
> > #include "kvm-s390.h"
> >
> > +/**
> > + * @struct deferred_priv
> > + * Represents a "leftover" protected VM that does not correspond to any
> > + * active KVM VM.
>
> Maybe something like:
> ...that is still registered with the Ultravisor but isn't registered
> with KVM anymore.

will fix

>
> > + */
> > +struct deferred_priv {
> > + struct list_head list;
> > + unsigned long old_table;
> > + u64 handle;
> > + void *stor_var;
> > + unsigned long stor_base;
> > +};
> > +
> > static void kvm_s390_clear_pv_state(struct kvm *kvm)
> > {
> > kvm->arch.pv.handle = 0;
> > @@ -163,6 +176,60 @@ static int kvm_s390_pv_alloc_vm(struct kvm *kvm)
> > return -ENOMEM;
> > }
> >
> > +/**
> > + * kvm_s390_pv_cleanup_deferred - Clean up one leftover protected VM.
> > + * @kvm the KVM that was associated with this leftover protected VM
> > + * @deferred details about the leftover protected VM that needs a clean up
> > + * Return: 0 in case of success, otherwise 1
> > + */
> > +static int kvm_s390_pv_cleanup_deferred(struct kvm *kvm, struct deferred_priv *deferred)
> > +{
> > + u16 rc, rrc;
> > + int cc;
> > +
> > + cc = uv_cmd_nodata(deferred->handle, UVC_CMD_DESTROY_SEC_CONF, &rc, &rrc);
> > + KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", rc, rrc);
> > + WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", rc, rrc);
> > + if (cc)
> > + return cc;
> > + /*
> > + * Intentionally leak unusable memory. If the UVC fails, the memory
> > + * used for the VM and its metadata is permanently unusable.
> > + * This can only happen in case of a serious KVM or hardware bug; it
> > + * is not expected to happen in normal operation.
> > + */
> > + free_pages(deferred->stor_base, get_order(uv_info.guest_base_stor_len));
> > + free_pages(deferred->old_table, CRST_ALLOC_ORDER);
> > + vfree(deferred->stor_var);
> > + return 0;
> > +}
> > +
> > +/**
> > + * kvm_s390_pv_cleanup_leftovers - Clean up all leftover protected VMs.
> > + * @kvm the KVM whose leftover protected VMs are to be cleaned up
> > + * Return: 0 in case of success, otherwise 1
> > + */
> > +static int kvm_s390_pv_cleanup_leftovers(struct kvm *kvm)
> > +{
> > + struct deferred_priv *deferred;
> > + int cc = 0;
> > +
> > + if (kvm->arch.pv.async_deinit)
> > + list_add(kvm->arch.pv.async_deinit, &kvm->arch.pv.need_cleanup);
> > +
> > + while (!list_empty(&kvm->arch.pv.need_cleanup)) {
> > + deferred = list_first_entry(&kvm->arch.pv.need_cleanup, typeof(*deferred), list);
> > + if (kvm_s390_pv_cleanup_deferred(kvm, deferred))
> > + cc = 1;
> > + else
> > + atomic_dec(&kvm->mm->context.protected_count);
> > + list_del(&deferred->list);
> > + kfree(deferred);
> > + }
> > + kvm->arch.pv.async_deinit = NULL;
> > + return cc;
> > +}
> > +
> > /* this should not fail, but if it does, we must not free the donated memory */
> > int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
> > {
> > @@ -190,6 +257,8 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
> > KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc);
> > WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc);
> >
> > + cc |= kvm_s390_pv_cleanup_leftovers(kvm);
> > +
> > return cc ? -EIO : 0;
> > }
> >
>