Re: [PATCH v1 02/13] KVM: s390: fake memslots for ucontrol VMs

Claudio Imbrenda
2025-01-10T16:18:22Z

On Fri, 10 Jan 2025 16:40:04 +0100
"Christoph Schlameuss" <schlameuss@linux.ibm.com> wrote:

> On Wed Jan 8, 2025 at 7:14 PM CET, Claudio Imbrenda wrote:
> > Create fake memslots for ucontrol VMs. The fake memslots identity-map
> > userspace.
> >
> > Now memslots will always be present, and ucontrol is not a special case
> > anymore.
> >
> > Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> > ---
> > arch/s390/kvm/kvm-s390.c | 42 ++++++++++++++++++++++++++++++++++++----
> > 1 file changed, 38 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> > index ecbdd7d41230..797b8503c162 100644
> > --- a/arch/s390/kvm/kvm-s390.c
> > +++ b/arch/s390/kvm/kvm-s390.c
> > @@ -59,6 +59,7 @@
> > #define LOCAL_IRQS 32
> > #define VCPU_IRQS_MAX_BUF (sizeof(struct kvm_s390_irq) * \
> > (KVM_MAX_VCPUS + LOCAL_IRQS))
> > +#define UCONTROL_SLOT_SIZE SZ_4T
> >
> > const struct _kvm_stats_desc kvm_vm_stats_desc[] = {
> > KVM_GENERIC_VM_STATS(),
> > @@ -3326,6 +3327,23 @@ void kvm_arch_free_vm(struct kvm *kvm)
> > __kvm_arch_free_vm(kvm);
> > }
> >
> > +static void kvm_s390_ucontrol_ensure_memslot(struct kvm *kvm, unsigned long addr)
> > +{
> > + struct kvm_userspace_memory_region2 region = {
> > + .slot = addr / UCONTROL_SLOT_SIZE,
> > + .memory_size = UCONTROL_SLOT_SIZE,
> > + .guest_phys_addr = ALIGN_DOWN(addr, UCONTROL_SLOT_SIZE),
> > + .userspace_addr = ALIGN_DOWN(addr, UCONTROL_SLOT_SIZE),
> > + };
> > + struct kvm_memory_slot *slot;
> > +
> > + mutex_lock(&kvm->slots_lock);
> > + slot = gfn_to_memslot(kvm, addr);
> > + if (!slot)
> > + __kvm_set_memory_region(kvm, &region);
>
> This will call into kvm_arch_commit_memory_region() where
> kvm->arch.gmap will still be NULL!

Oops!

will fix