Re: [PATCH 3/5] iommu: Limit iommu_attach/detach_device to devices with their own group

Joerg Roedel
2015-01-30T12:28:18Z

On Wed, Jan 28, 2015 at 02:35:24PM +0000, Will Deacon wrote:
> On Tue, Jan 27, 2015 at 12:08:57AM +0000, Joerg Roedel wrote:
> > @@ -51,6 +51,7 @@ struct iommu_group {
> > void (*iommu_data_release)(void *iommu_data);
> > char *name;
> > int id;
> > + unsigned dev_cnt;
>
> Is this actually used on a fast path, or can we just inspect the list of
> devices on the group instead?

Not really a fast path, but we have to hold the group mutex while
traversing the list, which could hurt performance somewhere else. Are
these 4 bytes a problem?

Joerg