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

[Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>]

On Fri, 10 Jan 2025 16:40:04 +0100
"Christoph Schlameuss" <schlameuss@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
> > ---
> >  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