Re: [PATCH v1 1/2] KVM: s390x: some utility functions for migration

[David Hildenbrand <david@redhat.com>]

On 15.01.2018 18:03, Claudio Imbrenda wrote:
> These are some utilty functions that will be used later on for storage
> attributes migration.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.vnet.ibm.com>
> ---
>  arch/s390/kvm/kvm-s390.c | 40 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 40 insertions(+)
> 
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 6f17031..100ea15 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -764,6 +764,14 @@ static void kvm_s390_sync_request_broadcast(struct kvm *kvm, int req)
>  		kvm_s390_sync_request(req, vcpu);
>  }
>  
> +static inline unsigned long *_cmma_bitmap(struct kvm_memory_slot *ms)

I think you can get rid of the "_" here. And ususally we use two _ ?

> +{
> +	unsigned long long len;
> +
> +	len = kvm_dirty_bitmap_bytes(ms) / sizeof(*ms->dirty_bitmap);

return (void *) ms->dirty_bitmap + kvm_dirty_bitmap_bytes(ms);

?

> +	return ms->dirty_bitmap + len;
> +}


> +
>  /*
>   * Must be called with kvm->srcu held to avoid races on memslots, and with
>   * kvm->lock to avoid races with ourselves and kvm_s390_vm_stop_migration.
> @@ -1512,6 +1520,38 @@ 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
> + * in a hole. In that case a memslot near the hole is returned.
> + */
> +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);
> +	}
> +
> +	return start;
> +}

This looks ugly, hope we can avoid this ....

> +
> +/*
>   * This function searches for the next page with dirty CMMA attributes, and
>   * saves the attributes in the buffer up to either the end of the buffer or
>   * until a block of at least KVM_S390_MAX_BIT_DISTANCE clean bits is found;
> 


-- 

Thanks,

David / dhildenb