[Cc +Shameer] Hi Filippo, On Mon, 5 Mar 2018 18:01:11 +0100 Filippo Sironi <sironi@xxxxxxxxx> wrote: > ... to avoid an unnecessary attach/detach of the iommu_group to the > newly created iommu_domain. This also saves us a context-cache and an > IOTLB flush. > > This is possible because allocating an iommu_domain for the iommu_group > we're attaching is enough to understand whether a fitting iommu_domain > already exists. The history here is that testing the coherency of the domain used to be based on the domain, allowing the IOMMU driver to support multiple hardware units with potentially different features. This has since become a bus_type attribute, but see Shameer's patch series adding support for IOVA lists: https://lkml.org/lkml/2018/2/21/355 This will returns similar requirements as we previously had for coherency as attributes such as geometry are per domain and I don't see that the IOMMU API guarantees that those attributes don't change based on the attached devices/groups. In fact there's quite a bit of code pending that assumes those attributes can change based on the attached devices. So, I don't think we can do this and enhance our IOVA handling. Thanks, Alex > Signed-off-by: Filippo Sironi <sironi@xxxxxxxxx> > Cc: Alex Williamson <alex.williamson@xxxxxxxxxx> > Cc: kvm@xxxxxxxxxxxxxxx > Cc: linux-kernel@xxxxxxxxxxxxxxx > --- > drivers/vfio/vfio_iommu_type1.c | 32 ++++++++++++++------------------ > 1 file changed, 14 insertions(+), 18 deletions(-) > > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > index 45657e2b1ff7..88359b4993f3 100644 > --- a/drivers/vfio/vfio_iommu_type1.c > +++ b/drivers/vfio/vfio_iommu_type1.c > @@ -1279,15 +1279,8 @@ static int vfio_iommu_type1_attach_group(void *iommu_data, > goto out_domain; > } > > - ret = iommu_attach_group(domain->domain, iommu_group); > - if (ret) > - goto out_domain; > - > resv_msi = vfio_iommu_has_sw_msi(iommu_group, &resv_msi_base); > > - INIT_LIST_HEAD(&domain->group_list); > - list_add(&group->next, &domain->group_list); > - > msi_remap = irq_domain_check_msi_remap() || > iommu_capable(bus, IOMMU_CAP_INTR_REMAP); > > @@ -1295,7 +1288,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data, > pr_warn("%s: No interrupt remapping support. Use the module param \"allow_unsafe_interrupts\" to enable VFIO IOMMU support on this platform\n", > __func__); > ret = -EPERM; > - goto out_detach; > + goto out_domain; > } > > if (iommu_capable(bus, IOMMU_CAP_CACHE_COHERENCY)) > @@ -1311,21 +1304,24 @@ static int vfio_iommu_type1_attach_group(void *iommu_data, > list_for_each_entry(d, &iommu->domain_list, next) { > if (d->domain->ops == domain->domain->ops && > d->prot == domain->prot) { > - iommu_detach_group(domain->domain, iommu_group); > - if (!iommu_attach_group(d->domain, iommu_group)) { > - list_add(&group->next, &d->group_list); > - iommu_domain_free(domain->domain); > - kfree(domain); > - mutex_unlock(&iommu->lock); > - return 0; > - } > - > - ret = iommu_attach_group(domain->domain, iommu_group); > + ret = iommu_attach_group(d->domain, iommu_group); > if (ret) > goto out_domain; > + list_add(&group->next, &d->group_list); > + iommu_domain_free(domain->domain); > + kfree(domain); > + mutex_unlock(&iommu->lock); > + return 0; > } > } > > + ret = iommu_attach_group(domain->domain, iommu_group); > + if (ret) > + goto out_domain; > + > + INIT_LIST_HEAD(&domain->group_list); > + list_add(&group->next, &domain->group_list); > + > vfio_test_domain_fgsp(domain); > > /* replay mappings on new domains */
