Messages in this thread | | | Subject | Re: [PATCH v11 07/14] s390/vfio-ap: sysfs attribute to display the guest's matrix | From | Tony Krowiak <> | Date | Fri, 13 Nov 2020 12:27:32 -0500 |
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On 10/28/20 4:17 AM, Halil Pasic wrote: > On Thu, 22 Oct 2020 13:12:02 -0400 > Tony Krowiak <akrowiak@linux.ibm.com> wrote: > >> +static ssize_t guest_matrix_show(struct device *dev, >> + struct device_attribute *attr, char *buf) >> +{ >> + ssize_t nchars; >> + struct mdev_device *mdev = mdev_from_dev(dev); >> + struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev); >> + >> + if (!vfio_ap_mdev_has_crycb(matrix_mdev)) >> + return -ENODEV; > I'm wondering, would it make sense to have guest_matrix display the would > be guest matrix when we don't have a KVM? With the filtering in > place, the question in what guest_matrix would my (assign) matrix result > right now if I were to hook up my vfio_ap_mdev to a guest seems a > legitimate one.
A couple of thoughts here: * The ENODEV informs the user that there is no guest running which makes sense to me given this interface displays the guest matrix. The alternative, which I considered, was to display an empty matrix (i.e., nothing). * This would be a pretty drastic change to the design because the shadow_apcb - which is what is displayed via this interface - is only updated when the guest is started and while it is running (i.e., hot plug of new adapters/domains). Making this change would require changing that entire design concept which I am reluctant to do at this point in the game.
> > >> + >> + mutex_lock(&matrix_dev->lock); >> + nchars = vfio_ap_mdev_matrix_show(&matrix_mdev->shadow_apcb, buf); >> + mutex_unlock(&matrix_dev->lock); >> + >> + return nchars; >> +} >> +static DEVICE_ATTR_RO(guest_matrix);
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