On Thu, Aug 10, 2023 at 03:20:07PM -0300, Jason Gunthorpe wrote: > On Thu, Jul 27, 2023 at 01:48:31PM +0800, Lu Baolu wrote: > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > > index 4ba3bb692993..3e4ff984aa85 100644 > > --- a/drivers/iommu/iommu.c > > +++ b/drivers/iommu/iommu.c > > @@ -302,7 +302,15 @@ static int dev_iommu_get(struct device *dev) > > return -ENOMEM; > > > > mutex_init(¶m->lock); > > + param->fault_param = kzalloc(sizeof(*param->fault_param), GFP_KERNEL); > > + if (!param->fault_param) { > > + kfree(param); > > + return -ENOMEM; > > + } > > + mutex_init(¶m->fault_param->lock); > > + INIT_LIST_HEAD(¶m->fault_param->faults); > > dev->iommu = param; > > This allocation seems pointless? > > If we always allocate the fault param then just don't make it a > pointer in the first place. > > The appeal of allocation would be to save a few bytes in the common > case that the driver doesn't support faulting. > > Which means the driver needs to make some call to enable faulting for > a device. In this case I'd continue to lazy free on release like this > patch does. For instance allocate the fault_param in iopf_queue_add_device() which is the only thing that needs it. Actually probably just merge struct iopf_device_param and iommu_fault_param ? When you call iopf_queue_add_device() it enables page faulting mode, does 1 additional allocation for all additional required per-device memory and thats it. Jason