Re: [PATCH v6 04/10] s390: vfio-ap: filter CRYCB bits for unavailable queue devices

[Tony Krowiak]

On 9/19/19 6:34 AM, Halil Pasic wrote:
> On Fri, 13 Sep 2019 17:26:52 -0400
> Tony Krowiak <akrowiak@xxxxxxxxxxxxx> wrote:
>
> > +static void vfio_ap_mdev_get_crycb_matrix(struct ap_matrix_mdev *matrix_mdev)
> > +{
> > +	unsigned long apid, apqi;
> > +	unsigned long masksz = BITS_TO_LONGS(AP_DEVICES) *
> > +			       sizeof(unsigned long);
> > +
> > +	memset(matrix_mdev->crycb.apm, 0, masksz);
> > +	memset(matrix_mdev->crycb.apm, 0, masksz);
> > +	memcpy(matrix_mdev->crycb.adm, matrix_mdev->matrix.adm, masksz);
> > +
> > +	for_each_set_bit_inv(apid, matrix_mdev->matrix.apm,
> > +			     matrix_mdev->matrix.apm_max + 1) {
> > +		for_each_set_bit_inv(apqi, matrix_mdev->matrix.aqm,
> > +				     matrix_mdev->matrix.aqm_max + 1) {
> > +			if (vfio_ap_find_queue(AP_MKQID(apid, apqi))) {
> > +				if (!test_bit_inv(apid, matrix_mdev->crycb.apm))
> > +					set_bit_inv(apid,
> > +						    matrix_mdev->crycb.apm);
> > +				if (!test_bit_inv(apqi, matrix_mdev->crycb.aqm))
> > +					set_bit_inv(apqi,
> > +						    matrix_mdev->crycb.aqm);
> > +			}
> > +		}
> > +	}
> > +}
>
> Even with the discussed typo fixed (zero crycb.aqm) this procedure does
> not make sense to me. :(
>
> If in doubt please consider the following example:
> matrix_mdev->matrix.apm and matrix_mdev->matrix.aqm have both just bits
> 0 and 1 set (i.e. first byte 0xC0 the rest of the bytes 0x0). Queues
> bound to the vfio_ap driver (0,0), (0,1), (1,0); not bound to vfio_ap is
> however (1,1). If I read this correctly this filtering logic would grant
> access to (1,1) which seems to contradict with the stated intention.

Yep, I see your point. I'll have to rework this code.

> Regards,
> Halil