Hi Alex,
On 7/31/20 5:17 AM, Alex Williamson wrote:
On Thu, 30 Jul 2020 10:41:32 +0800
Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> wrote:
Hi Alex,
On 7/30/20 4:32 AM, Alex Williamson wrote:
On Tue, 14 Jul 2020 13:57:03 +0800
Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> wrote:
Replace iommu_aux_at(de)tach_device() with iommu_aux_at(de)tach_group().
It also saves the IOMMU_DEV_FEAT_AUX-capable physcail device in the
vfio_group data structure so that it could be reused in other places.
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
drivers/vfio/vfio_iommu_type1.c | 44 ++++++---------------------------
1 file changed, 7 insertions(+), 37 deletions(-)
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 5e556ac9102a..f8812e68de77 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -100,6 +100,7 @@ struct vfio_dma {
struct vfio_group {
struct iommu_group *iommu_group;
struct list_head next;
+ struct device *iommu_device;
bool mdev_group; /* An mdev group */
bool pinned_page_dirty_scope;
};
@@ -1627,45 +1628,13 @@ static struct device *vfio_mdev_get_iommu_device(struct device *dev)
return NULL;
}
-static int vfio_mdev_attach_domain(struct device *dev, void *data)
-{
- struct iommu_domain *domain = data;
- struct device *iommu_device;
-
- iommu_device = vfio_mdev_get_iommu_device(dev);
- if (iommu_device) {
- if (iommu_dev_feature_enabled(iommu_device, IOMMU_DEV_FEAT_AUX))
- return iommu_aux_attach_device(domain, iommu_device);
- else
- return iommu_attach_device(domain, iommu_device);
- }
-
- return -EINVAL;
-}
-
-static int vfio_mdev_detach_domain(struct device *dev, void *data)
-{
- struct iommu_domain *domain = data;
- struct device *iommu_device;
-
- iommu_device = vfio_mdev_get_iommu_device(dev);
- if (iommu_device) {
- if (iommu_dev_feature_enabled(iommu_device, IOMMU_DEV_FEAT_AUX))
- iommu_aux_detach_device(domain, iommu_device);
- else
- iommu_detach_device(domain, iommu_device);
- }
-
- return 0;
-}
-
static int vfio_iommu_attach_group(struct vfio_domain *domain,
struct vfio_group *group)
{
if (group->mdev_group)
- return iommu_group_for_each_dev(group->iommu_group,
- domain->domain,
- vfio_mdev_attach_domain);
+ return iommu_aux_attach_group(domain->domain,
+ group->iommu_group,
+ group->iommu_device);
No, we previously iterated all devices in the group and used the aux
interface only when we have an iommu_device supporting aux. If we
simply assume an mdev group only uses an aux domain we break existing
users, ex. SR-IOV VF backed mdevs. Thanks,
Oh, yes. Sorry! I didn't consider the physical device backed mdevs
cases.
Looked into this part of code, it seems that there's a lock issue here.
The group->mutex is held in iommu_group_for_each_dev() and will be
acquired again in iommu_attach_device().
These are two different groups. We walk the devices in the mdev's
group with iommu_group_for_each_dev(), holding the mdev's group lock,
but we call iommu_attach_device() with iommu_device, which results in
acquiring the lock for the iommu_device's group.
You are right. Sorry for the noise. Please ignore it.
How about making it like:
static int vfio_iommu_attach_group(struct vfio_domain *domain,
struct vfio_group *group)
{
if (group->mdev_group) {
struct device *iommu_device = group->iommu_device;
if (WARN_ON(!iommu_device))
return -EINVAL;
if (iommu_dev_feature_enabled(iommu_device,
IOMMU_DEV_FEAT_AUX))
return iommu_aux_attach_device(domain->domain,
iommu_device);
else
return iommu_attach_device(domain->domain,
iommu_device);
} else {
return iommu_attach_group(domain->domain,
group->iommu_group);
}
}
The caller (vfio_iommu_type1_attach_group) has guaranteed that all mdevs
in an iommu group should be derived from a same physical device.
Have we?
We have done this with below.
static int vfio_mdev_iommu_device(struct device *dev, void *data)
{
struct device **old = data, *new;
new = vfio_mdev_get_iommu_device(dev);
if (!new || (*old && *old != new))
return -EINVAL;
*old = new;
return 0;
}
But I agree that as a generic iommu aux-domain api, we shouldn't put
this limited assumption in it.
iommu_attach_device() will fail if the group is not
singleton, but that's just encouraging us to use the _attach_group()
interface where the _attach_device() interface is relegated to special
cases. Ideally we'd get out of those special cases and create an
_attach_group() for aux that doesn't further promote these notions.
Yes. Fair enough.
Any thoughts?
See my reply to Kevin, I'm thinking we need to provide a callback that
can enlighten the IOMMU layer to be able to do _attach_group() with
aux or separate IOMMU backed devices.
Thanks for the guide. I will check your reply.
Best regards,
baolu
