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Date: Wed, 1 Apr 2020 17:49:32 +0200
From: Jean-Philippe Brucker <jean-philippe@...aro.org>
To: Robin Murphy <robin.murphy@....com>
Cc: Bharat Bhushan <bbhushan2@...vell.com>, joro@...tes.org,
mst@...hat.com, jasowang@...hat.com,
virtualization@...ts.linux-foundation.org,
iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
eric.auger.pro@...il.com, eric.auger@...hat.com
Subject: Re: [RFC PATCH v2] iommu/virtio: Use page size bitmap supported by
endpoint
On Wed, Apr 01, 2020 at 02:00:13PM +0100, Robin Murphy wrote:
> On 2020-04-01 12:38 pm, Bharat Bhushan wrote:
> > Different endpoint can support different page size, probe
> > endpoint if it supports specific page size otherwise use
> > global page sizes.
> >
> > Signed-off-by: Bharat Bhushan <bbhushan2@...vell.com>
> > ---
> > drivers/iommu/virtio-iommu.c | 33 +++++++++++++++++++++++++++----
> > include/uapi/linux/virtio_iommu.h | 7 +++++++
> > 2 files changed, 36 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
> > index cce329d71fba..c794cb5b7b3e 100644
> > --- a/drivers/iommu/virtio-iommu.c
> > +++ b/drivers/iommu/virtio-iommu.c
> > @@ -78,6 +78,7 @@ struct viommu_endpoint {
> > struct viommu_dev *viommu;
> > struct viommu_domain *vdomain;
> > struct list_head resv_regions;
> > + u64 pgsize_bitmap;
> > };
> > struct viommu_request {
> > @@ -415,6 +416,20 @@ static int viommu_replay_mappings(struct viommu_domain *vdomain)
> > return ret;
> > }
> > +static int viommu_set_pgsize_bitmap(struct viommu_endpoint *vdev,
> > + struct virtio_iommu_probe_pgsize_mask *mask,
> > + size_t len)
> > +
> > +{
> > + u64 pgsize_bitmap = le64_to_cpu(mask->pgsize_bitmap);
> > +
> > + if (len < sizeof(*mask))
> > + return -EINVAL;
> > +
> > + vdev->pgsize_bitmap = pgsize_bitmap;
> > + return 0;
> > +}
> > +
> > static int viommu_add_resv_mem(struct viommu_endpoint *vdev,
> > struct virtio_iommu_probe_resv_mem *mem,
> > size_t len)
> > @@ -494,11 +509,13 @@ static int viommu_probe_endpoint(struct viommu_dev *viommu, struct device *dev)
> > while (type != VIRTIO_IOMMU_PROBE_T_NONE &&
> > cur < viommu->probe_size) {
> > len = le16_to_cpu(prop->length) + sizeof(*prop);
> > -
Whitespace change
> > switch (type) {
> > case VIRTIO_IOMMU_PROBE_T_RESV_MEM:
> > ret = viommu_add_resv_mem(vdev, (void *)prop, len);
> > break;
> > + case VIRTIO_IOMMU_PROBE_T_PAGE_SIZE_MASK:
> > + ret = viommu_set_pgsize_bitmap(vdev, (void *)prop, len);
> > + break;
> > default:
> > dev_err(dev, "unknown viommu prop 0x%x\n", type);
> > }
> > @@ -607,16 +624,23 @@ static struct iommu_domain *viommu_domain_alloc(unsigned type)
> > return &vdomain->domain;
> > }
> > -static int viommu_domain_finalise(struct viommu_dev *viommu,
> > +static int viommu_domain_finalise(struct viommu_endpoint *vdev,
> > struct iommu_domain *domain)
> > {
> > int ret;
> > struct viommu_domain *vdomain = to_viommu_domain(domain);
> > + struct viommu_dev *viommu = vdev->viommu;
> > vdomain->viommu = viommu;
> > vdomain->map_flags = viommu->map_flags;
> > - domain->pgsize_bitmap = viommu->pgsize_bitmap;
> > + /* Devices in same domain must support same size pages */
>
> AFAICS what the code appears to do is enforce that the first endpoint
> attached to any domain has the same pgsize_bitmap as the most recently
> probed viommu_dev instance, then ignore any subsequent endpoints attached to
> the same domain. Thus I'm not sure that comment is accurate.
>
Yes viommu_domain_finalise() is only called once. What I had in mind is
something like:
---- 8< ----
diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
index 750f69c49b95..8303b7b513ff 100644
--- a/drivers/iommu/virtio-iommu.c
+++ b/drivers/iommu/virtio-iommu.c
@@ -639,6 +639,29 @@ static int viommu_domain_finalise(struct viommu_endpoint *vdev,
return 0;
}
+/*
+ * Check whether the endpoint's capabilities are compatible with other endpoints
+ * in the domain. Report any inconsistency.
+ */
+static bool viommu_endpoint_is_compatible(struct viommu_endpoint *vdev,
+ struct viommu_domain *vdomain)
+{
+ struct device *dev = vdev->dev;
+
+ if (vdomain->viommu != vdev->viommu) {
+ dev_err(dev, "cannot attach to foreign vIOMMU\n");
+ return false;
+ }
+
+ if (vdomain->domain.pgsize_bitmap != vdev->pgsize_bitmap) {
+ dev_err(dev, "incompatible domain bitmap 0x%lx != 0x%lx\n",
+ vdomain->domain.pgsize_bitmap, vdev->pgsize_bitmap);
+ return false;
+ }
+
+ return true;
+}
+
static void viommu_domain_free(struct iommu_domain *domain)
{
struct viommu_domain *vdomain = to_viommu_domain(domain);
@@ -670,9 +693,8 @@ static int viommu_attach_dev(struct iommu_domain *domain, struct device *dev)
* owns it.
*/
ret = viommu_domain_finalise(vdev, domain);
- } else if (vdomain->viommu != vdev->viommu) {
- dev_err(dev, "cannot attach to foreign vIOMMU\n");
- ret = -EXDEV;
+ } else if (!viommu_endpoint_is_compatible(vdev, vdomain)) {
+ ret = -EINVAL;
}
mutex_unlock(&vdomain->mutex);
---- >8 ----
>
> > + if ((domain->pgsize_bitmap != viommu->pgsize_bitmap) &&
> > + (domain->pgsize_bitmap != vdev->pgsize_bitmap))
> > + return -EINVAL;
> > +
> > + domain->pgsize_bitmap = vdev->pgsize_bitmap;
> > +
> > domain->geometry = viommu->geometry;
> > ret = ida_alloc_range(&viommu->domain_ids, viommu->first_domain,
> > @@ -657,7 +681,7 @@ static int viommu_attach_dev(struct iommu_domain *domain, struct device *dev)
> > * Properly initialize the domain now that we know which viommu
> > * owns it.
> > */
> > - ret = viommu_domain_finalise(vdev->viommu, domain);
> > + ret = viommu_domain_finalise(vdev, domain);
> > } else if (vdomain->viommu != vdev->viommu) {
> > dev_err(dev, "cannot attach to foreign vIOMMU\n");
> > ret = -EXDEV;
> > @@ -875,6 +899,7 @@ static int viommu_add_device(struct device *dev)
> > vdev->dev = dev;
> > vdev->viommu = viommu;
> > + vdev->pgsize_bitmap = viommu->pgsize_bitmap;
> > INIT_LIST_HEAD(&vdev->resv_regions);
> > fwspec->iommu_priv = vdev;
> > diff --git a/include/uapi/linux/virtio_iommu.h b/include/uapi/linux/virtio_iommu.h
> > index 237e36a280cb..dc9d3f40bcd8 100644
> > --- a/include/uapi/linux/virtio_iommu.h
> > +++ b/include/uapi/linux/virtio_iommu.h
> > @@ -111,6 +111,7 @@ struct virtio_iommu_req_unmap {
> > #define VIRTIO_IOMMU_PROBE_T_NONE 0
> > #define VIRTIO_IOMMU_PROBE_T_RESV_MEM 1
> > +#define VIRTIO_IOMMU_PROBE_T_PAGE_SIZE_MASK 2
> > #define VIRTIO_IOMMU_PROBE_T_MASK 0xfff
> > @@ -119,6 +120,12 @@ struct virtio_iommu_probe_property {
> > __le16 length;
> > };
> > +struct virtio_iommu_probe_pgsize_mask {
> > + struct virtio_iommu_probe_property head;
> > + __u8 reserved[4];
> > + __u64 pgsize_bitmap;
Should be __le64
Thanks,
Jean
> > +};
> > +
> > #define VIRTIO_IOMMU_RESV_MEM_T_RESERVED 0
> > #define VIRTIO_IOMMU_RESV_MEM_T_MSI 1
> >
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