> From: Tian, Kevin <kevin.tian@xxxxxxxxx> > Sent: Monday, March 30, 2020 4:41 PM > To: Liu, Yi L <yi.l.liu@xxxxxxxxx>; alex.williamson@xxxxxxxxxx; > Subject: RE: [PATCH v1 2/8] vfio/type1: Add vfio_iommu_type1 parameter for quota > tuning > > > From: Liu, Yi L <yi.l.liu@xxxxxxxxx> > > Sent: Sunday, March 22, 2020 8:32 PM > > > > From: Liu Yi L <yi.l.liu@xxxxxxxxx> > > > > This patch adds a module option to make the PASID quota tunable by > > administrator. > > > > TODO: needs to think more on how to make the tuning to be per-process. > > > > Previous discussions: > > https://patchwork.kernel.org/patch/11209429/ > > > > Cc: Kevin Tian <kevin.tian@xxxxxxxxx> > > CC: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx> > > Cc: Alex Williamson <alex.williamson@xxxxxxxxxx> > > Cc: Eric Auger <eric.auger@xxxxxxxxxx> > > Cc: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx> > > Signed-off-by: Liu Yi L <yi.l.liu@xxxxxxxxx> > > --- > > drivers/vfio/vfio.c | 8 +++++++- > > drivers/vfio/vfio_iommu_type1.c | 7 ++++++- > > include/linux/vfio.h | 3 ++- > > 3 files changed, 15 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c > > index d13b483..020a792 100644 > > --- a/drivers/vfio/vfio.c > > +++ b/drivers/vfio/vfio.c > > @@ -2217,13 +2217,19 @@ struct vfio_mm *vfio_mm_get_from_task(struct > > task_struct *task) > > } > > EXPORT_SYMBOL_GPL(vfio_mm_get_from_task); > > > > -int vfio_mm_pasid_alloc(struct vfio_mm *vmm, int min, int max) > > +int vfio_mm_pasid_alloc(struct vfio_mm *vmm, int quota, int min, int max) > > { > > ioasid_t pasid; > > int ret = -ENOSPC; > > > > mutex_lock(&vmm->pasid_lock); > > > > + /* update quota as it is tunable by admin */ > > + if (vmm->pasid_quota != quota) { > > + vmm->pasid_quota = quota; > > + ioasid_adjust_set(vmm->ioasid_sid, quota); > > + } > > + > > It's a bit weird to have quota adjusted in the alloc path, since the latter might > be initiated by non-privileged users. Why not doing the simple math in vfio_ > create_mm to set the quota when the ioasid set is created? even in the future > you may allow per-process quota setting, that should come from separate > privileged path instead of thru alloc.. The reason is the kernel parameter modification has no event which can be used to adjust the quota. So I chose to adjust it in pasid_alloc path. If it's not good, how about adding one more IOCTL to let user- space trigger a quota adjustment event? Then even non-privileged user could trigger quota adjustment, the quota is actually controlled by privileged user. How about your opinion? Regards, Yi Liu
