On Wed, 16 May 2018 08:23:20 -0600 Alex Williamson <alex.williamson@xxxxxxxxxx> wrote: > On Wed, 16 May 2018 11:05:06 +0200 > Cornelia Huck <cohuck@xxxxxxxxxx> wrote: > > > On Tue, 15 May 2018 14:17:04 -0600 > > Alex Williamson <alex.williamson@xxxxxxxxxx> wrote: > > > > > When we create an mdev device, we check for duplicates against the > > > parent device and return -EEXIST if found, but the mdev device > > > namespace is global since we'll link all devices from the bus. We do > > > catch this later in sysfs_do_create_link_sd() to return -EEXIST, but > > > with it comes a kernel warning and stack trace for trying to create > > > duplicate sysfs links, which makes it an undesirable response. > > > > > > Therefore we should really be looking for duplicates across all mdev > > > parent devices, or as implemented here, against our mdev device list. > > > > > > Notably, mdev_parent.lock really only seems to be serializing device > > > creation and removal per parent. I'm not sure if this is necessary, > > > mdev vendor drivers could easily provide this serialization if it > > > is required, but a side-effect of holding the mdev_list_lock to > > > protect the namespace is actually greater serialization across the > > > create and remove paths, so mdev_parent.lock is removed. If we can > > > show that vendor drivers handle the create/remove paths themselves, > > > perhaps we can refine the locking granularity. > > > > I'm not sure whether more locking granularity on the create/remove > > paths is really worth the effort. > > Perhaps not, but I thought I should at least mention it as a > consideration. > > > > Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx> > > > --- > > > drivers/vfio/mdev/mdev_core.c | 79 ++++++++++---------------------------- > > > drivers/vfio/mdev/mdev_private.h | 1 > > > 2 files changed, 20 insertions(+), 60 deletions(-) > > > > In general, I think this patch makes sense; some nits below. > > > > > > > > diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c > > > index 126991046eb7..3d8898a2baaf 100644 > > > --- a/drivers/vfio/mdev/mdev_core.c > > > +++ b/drivers/vfio/mdev/mdev_core.c > > > > > @@ -376,12 +346,13 @@ int mdev_device_remove(struct device *dev, bool force_remove) > > > struct mdev_device *mdev, *tmp; > > > struct mdev_parent *parent; > > > struct mdev_type *type; > > > - int ret; > > > + int ret = 0; > > > > I don't think you need to init this, as ret should either be set to > > -ENODEV or the return code of mdev_device_remove_ops(), shouldn't it? > > Yep, I think this is a leftover from before I decided I should goto a > common out, it's unnecessary now. Removed. OK, with that change Reviewed-by: Cornelia Huck <cohuck@xxxxxxxxxx>
