On 2022/4/12 15:19, Tian, Kevin wrote:
From: Lu Baolu <[email protected]>
Sent: Sunday, April 10, 2022 6:25 PM
+struct iommu_sva *
+iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, void
*drvdata)
+{
+ int ret = -EINVAL;
+ struct iommu_sva *handle;
+ struct iommu_domain *domain;
+ struct iommu_sva_ioas *ioas;
+
+ /*
+ * TODO: Remove the drvdata parameter after kernel PASID support
is
+ * enabled for the idxd driver.
+ */
+ if (drvdata)
+ return ERR_PTR(-EOPNOTSUPP);
+
+ /* Allocate mm->pasid if necessary. */
+ ret = iommu_sva_alloc_pasid(mm, 1, (1U << dev->iommu->pasid_bits)
- 1);
+ if (ret)
+ return ERR_PTR(ret);
+
+ mutex_lock(&iommu_sva_lock);
+ ioas = iommu_sva_ioas_get(mm, mm->pasid);
+ if (!ioas) {
+ ret = -ENOMEM;
ioas can be NULL for multiple reasons, e.g. :
1) ioas->mm != mm;
2) kzalloc failure;
3) xa_store failure;
It's more sensible to return error from iommu_sva_ioas_get() directly.
Fair enough.
+ goto out_unlock;
+ }
+
+ /* Search for an existing bond. */
+ list_for_each_entry(handle, &ioas->bonds, node) {
+ if (handle->dev == dev) {
+ refcount_inc(&handle->users);
+ /* No new bond, drop the counter. */
+ iommu_sva_ioas_put(ioas);
+ goto out_success;
+ }
+ }
+
+ handle = kzalloc(sizeof(*handle), GFP_KERNEL);
s/handle/bond/?
"handle" is used in the previous implementation but "bond" looks better
to read. :-)
+ if (!handle) {
+ ret = -ENOMEM;
+ goto out_put_ioas;
+ }
+
+ /* The reference to ioas will be kept until domain free. */
+ domain = iommu_sva_alloc_domain(dev, ioas);
Shouldn't we first try whether existing domains are compatible to this
device?
If we think that here domain represents a hardware pagetable actually
used by IOMMU for a {device, pasid}, we are able to use per-{device,
pasid} domain without checking compatibility. Sharing a domain among
devices under the same IOMMU may be an optimization. That could be done
in the IOMMU driver just like what vt-d driver is doing for pass-through
DMA domains.
@@ -1952,6 +1954,7 @@ EXPORT_SYMBOL_GPL(iommu_domain_alloc);
void iommu_domain_free(struct iommu_domain *domain)
{
iommu_put_dma_cookie(domain);
+ iommu_sva_ioas_put(domain->sva_ioas);
domain->ops->free(domain);
}
is it good to have general iommu_domain_free() to always call a put()
function for a specific domain type? Why cannot it be done before
calling iommu_domain_free() in sva-lib.c?
It's better to have a generic free() helper since an sva domain could be
freed outside of iommu sva code as you can see in the following patches.
Best regards,
baolu
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