virtio-devices: iommu: Support multiple endpoints per domain

Based on the VIRTIO specification, we must be able to support multiple
endpoints per domain. This is fixed along with the introduction of some
simplification regarding how we can retrieve the external mapping
directly based on the endpoint.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

virtio-devices/src/iommu.rs

@@ -346,7 +346,6 @@ impl Request {
         desc_chain: &mut DescriptorChain<GuestMemoryLoadGuard<GuestMemoryMmap>>,
         mapping: &Arc<IommuMapping>,
         ext_mapping: &BTreeMap<u32, Arc<dyn ExternalDmaMapping>>,
-        ext_domain_mapping: &mut BTreeMap<u32, Arc<dyn ExternalDmaMapping>>,
         msi_iova_space: (u64, u64),
     ) -> result::Result<usize, Error> {
         let desc = desc_chain
@@ -402,13 +401,6 @@ impl Request {
                 // Add endpoint associated with specific domain
                 mapping.endpoints.write().unwrap().insert(endpoint, domain);
 
-                // If the endpoint is part of the list of devices with an
-                // external mapping, insert a new entry for the corresponding
-                // domain, with the same reference to the trait.
-                if let Some(map) = ext_mapping.get(&endpoint) {
-                    ext_domain_mapping.insert(domain, map.clone());
-                }
-
                 // Add new domain with no mapping if the entry didn't exist yet
                 let mut mappings = mapping.mappings.write().unwrap();
                 mappings.entry(domain).or_insert_with(BTreeMap::new);
@@ -430,16 +422,24 @@ impl Request {
                 let domain = req.domain;
                 let endpoint = req.endpoint;
 
-                // If the endpoint is part of the list of devices with an
-                // external mapping, remove the entry for the corresponding
-                // domain.
-                if ext_mapping.contains_key(&endpoint) {
-                    ext_domain_mapping.remove(&domain);
-                }
-
                 // Remove endpoint associated with specific domain
                 mapping.endpoints.write().unwrap().remove(&endpoint);
 
+                // After all endpoints have been successfully detached from a
+                // domain, the domain can be removed. This means we must remove
+                // the mappings associated with this domain.
+                if mapping
+                    .endpoints
+                    .write()
+                    .unwrap()
+                    .iter()
+                    .filter(|(_, &d)| d == domain)
+                    .count()
+                    == 0
+                {
+                    mapping.mappings.write().unwrap().remove(&domain);
+                }
+
                 0
             }
             VIRTIO_IOMMU_T_MAP => {
@@ -455,13 +455,24 @@ impl Request {
 
                 // Copy the value to use it as a proper reference.
                 let domain = req.domain;
+                // Find the list of endpoints attached to the given domain.
+                let endpoints: Vec<u32> = mapping
+                    .endpoints
+                    .write()
+                    .unwrap()
+                    .iter()
+                    .filter(|(_, &d)| d == domain)
+                    .map(|(&e, _)| e)
+                    .collect();
 
                 // Trigger external mapping if necessary.
-                if let Some(ext_map) = ext_domain_mapping.get(&domain) {
+                for endpoint in endpoints {
-                    let size = req.virt_end - req.virt_start + 1;
+                    if let Some(ext_map) = ext_mapping.get(&endpoint) {
-                    ext_map
+                        let size = req.virt_end - req.virt_start + 1;
-                        .map(req.virt_start, req.phys_start, size)
+                        ext_map
-                        .map_err(Error::ExternalMapping)?;
+                            .map(req.virt_start, req.phys_start, size)
+                            .map_err(Error::ExternalMapping)?;
+                    }
                 }
 
                 // Add new mapping associated with the domain
@@ -493,16 +504,27 @@ impl Request {
                 // Copy the value to use it as a proper reference.
                 let domain = req.domain;
                 let virt_start = req.virt_start;
+                // Find the list of endpoints attached to the given domain.
+                let endpoints: Vec<u32> = mapping
+                    .endpoints
+                    .write()
+                    .unwrap()
+                    .iter()
+                    .filter(|(_, &d)| d == domain)
+                    .map(|(&e, _)| e)
+                    .collect();
 
                 // Trigger external unmapping if necessary.
-                if let Some(ext_map) = ext_domain_mapping.get(&domain) {
+                for endpoint in endpoints {
-                    let size = req.virt_end - virt_start + 1;
+                    if let Some(ext_map) = ext_mapping.get(&endpoint) {
-                    ext_map
+                        let size = req.virt_end - virt_start + 1;
-                        .unmap(virt_start, size)
+                        ext_map
-                        .map_err(Error::ExternalUnmapping)?;
+                            .unmap(virt_start, size)
+                            .map_err(Error::ExternalUnmapping)?;
+                    }
                 }
 
-                // Add new mapping associated with the domain
+                // Remove mapping associated with the domain
                 if let Some(entry) = mapping.mappings.write().unwrap().get_mut(&domain) {
                     entry.remove(&virt_start);
                 }
@@ -573,7 +595,6 @@ struct IommuEpollHandler {
     pause_evt: EventFd,
     mapping: Arc<IommuMapping>,
     ext_mapping: Arc<Mutex<BTreeMap<u32, Arc<dyn ExternalDmaMapping>>>>,
-    ext_domain_mapping: BTreeMap<u32, Arc<dyn ExternalDmaMapping>>,
     msi_iova_space: (u64, u64),
 }
 
@@ -586,7 +607,6 @@ impl IommuEpollHandler {
                 &mut desc_chain,
                 &self.mapping,
                 &self.ext_mapping.lock().unwrap(),
-                &mut self.ext_domain_mapping,
                 self.msi_iova_space,
             ) {
                 Ok(len) => len as u32,
@@ -900,7 +920,6 @@ impl VirtioDevice for Iommu {
             pause_evt,
             mapping: self.mapping.clone(),
             ext_mapping: self.ext_mapping.clone(),
-            ext_domain_mapping: BTreeMap::new(),
             msi_iova_space: self.msi_iova_space,
         };