2018-01-22 10:08+0100, Christian Borntraeger:
> On 01/18/2018 01:56 PM, Claudio Imbrenda wrote:
> > These are some utilty functions that will be used later on for storage
> > attributes migration.
> >
> > Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxxxxxxx>
> > ---
> > arch/s390/kvm/kvm-s390.c | 32 ++++++++++++++++++++++++++++++++
> > arch/s390/kvm/kvm-s390.h | 6 ++++++
> > 2 files changed, 38 insertions(+)
> >
> > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> > index 6f17031..5a69334 100644
> > --- a/arch/s390/kvm/kvm-s390.c
> > +++ b/arch/s390/kvm/kvm-s390.c
> > @@ -1512,6 +1512,38 @@ static long kvm_s390_set_skeys(struct kvm *kvm, struct kvm_s390_skeys *args)
> > #define KVM_S390_CMMA_SIZE_MAX ((u32)KVM_S390_SKEYS_MAX)
> >
> > /*
> > + * Similar to gfn_to_memslot, but returns a memslot also when the address falls
>
> gfn_to_memslot returns a memslot, this returns an int?
>
> > + * in a hole. In that case a memslot near the hole is returned.
>
> Can you please clarify that statement? Will it be the slot that is closest
> in terms of bytes or what? Maybe also provide a use case and an example
> > + */
> > +static int gfn_to_memslot_approx(struct kvm *kvm, gfn_t gfn)
> > +{
> > + struct kvm_memslots *slots = kvm_memslots(kvm);
> > + int start = 0, end = slots->used_slots;
> > + int slot = atomic_read(&slots->lru_slot);
> > + struct kvm_memory_slot *memslots = slots->memslots;
> > +
> > + if (gfn >= memslots[slot].base_gfn &&
> > + gfn < memslots[slot].base_gfn + memslots[slot].npages)
> > + return slot;
> > +
> > + while (start < end) {
> > + slot = start + (end - start) / 2;
> > +
> > + if (gfn >= memslots[slot].base_gfn)
> > + end = slot;
> > + else
> > + start = slot + 1;
> > + }
> > +
> > + if (gfn >= memslots[start].base_gfn &&
> > + gfn < memslots[start].base_gfn + memslots[start].npages) {
> > + atomic_set(&slots->lru_slot, start);
> > + }
>
> Another question for Paolo/Radim. In case we need such function, would
> it be better in common code (kvm_main.c)
Please keep it in s390 and don't do it in the best case.
The function doesn't look reusable. If a gfn isn't in a slot, then we
shouldn't be using slots to work with it.
I don't understand why CMMA need adresses in the gaps, so I can't
provide a good idea here -- maybe we can add slots where needed?
