Re: [PATCH 3/6] KVM: PPC: Book3S HV: Use IDA allocator for LPID allocator

[Fabiano Rosas <farosas@linux.ibm.com>]

Nicholas Piggin <npiggin@gmail.com> writes:

> This removes the fixed-size lpid_inuse array.
>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---

Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>

>  arch/powerpc/kvm/powerpc.c | 25 +++++++++++++------------
>  1 file changed, 13 insertions(+), 12 deletions(-)
>
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 102993462872..c527a5751b46 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -2453,20 +2453,22 @@ long kvm_arch_vm_ioctl(struct file *filp,
>  	return r;
>  }
>
> -static unsigned long lpid_inuse[BITS_TO_LONGS(KVMPPC_NR_LPIDS)];
> +static DEFINE_IDA(lpid_inuse);
>  static unsigned long nr_lpids;
>
>  long kvmppc_alloc_lpid(void)
>  {
> -	long lpid;
> +	int lpid;
>
> -	do {
> -		lpid = find_first_zero_bit(lpid_inuse, KVMPPC_NR_LPIDS);
> -		if (lpid >= nr_lpids) {
> +	/* The host LPID must always be 0 (allocation starts at 1) */
> +	lpid = ida_alloc_range(&lpid_inuse, 1, nr_lpids - 1, GFP_KERNEL);
> +	if (lpid < 0) {
> +		if (lpid == -ENOMEM)
> +			pr_err("%s: Out of memory\n", __func__);
> +		else
>  			pr_err("%s: No LPIDs free\n", __func__);
> -			return -ENOMEM;
> -		}
> -	} while (test_and_set_bit(lpid, lpid_inuse));
> +		return -ENOMEM;
> +	}
>
>  	return lpid;
>  }
> @@ -2474,15 +2476,14 @@ EXPORT_SYMBOL_GPL(kvmppc_alloc_lpid);
>
>  void kvmppc_free_lpid(long lpid)
>  {
> -	clear_bit(lpid, lpid_inuse);
> +	ida_free(&lpid_inuse, lpid);
>  }
>  EXPORT_SYMBOL_GPL(kvmppc_free_lpid);
>
> +/* nr_lpids_param includes the host LPID */
>  void kvmppc_init_lpid(unsigned long nr_lpids_param)
>  {
> -	nr_lpids = min_t(unsigned long, KVMPPC_NR_LPIDS, nr_lpids_param);
> -	memset(lpid_inuse, 0, sizeof(lpid_inuse));
> -	set_bit(0, lpid_inuse); /* The host LPID must always be 0 */
> +	nr_lpids = nr_lpids_param;
>  }
>  EXPORT_SYMBOL_GPL(kvmppc_init_lpid);