vhost-user-backend: Add support for Xen memory mappings

Migrate to a newer version of the vhost and other dependencies and add
support for xen memory mappings. Add a corresponding xen feature for
vhost-user-backend crate.

Signed-off-by: Viresh Kumar <[email protected]>

Author: vireshk

crates/vhost-user-backend/Cargo.toml

@@ -8,17 +8,20 @@ repository = "https://github.com/rust-vmm/vhost"
 edition = "2018"
 license = "Apache-2.0"
 
+[features]
+xen = ["vm-memory/xen", "vhost/xen"]
+
 [dependencies]
 libc = "0.2.39"
 log = "0.4.17"
-vhost = { path = "../vhost", version = "0.7", features = ["vhost-user-slave"] }
-virtio-bindings = "0.2.0"
-virtio-queue = "0.8.0"
-vm-memory = { version = "0.11.0", features = ["backend-mmap", "backend-atomic"] }
+vhost = { path = "../vhost", version = "0.8", features = ["vhost-user-slave"] }
+virtio-bindings = "0.2.1"
+virtio-queue = "0.9.0"
+vm-memory = { version = "0.12.0", features = ["backend-mmap", "backend-atomic"] }
 vmm-sys-util = "0.11.0"
 
 [dev-dependencies]
 nix = "0.26"
-vhost = { path = "../vhost", version = "0.7", features = ["test-utils", "vhost-user-master", "vhost-user-slave"] }
-vm-memory = { version = "0.11.0", features = ["backend-mmap", "backend-atomic", "backend-bitmap"] }
+vhost = { path = "../vhost", version = "0.8", features = ["test-utils", "vhost-user-master", "vhost-user-slave"] }
+vm-memory = { version = "0.12.0", features = ["backend-mmap", "backend-atomic", "backend-bitmap"] }
 tempfile = "3.2.0"

crates/vhost-user-backend/README.md

@@ -98,6 +98,18 @@ impl VhostUserBackendMut for VhostUserService {
 }
 ```
 
+## Xen support
+
+Supporting Xen requires special handling while mapping the guest memory. The
+`vm-memory` crate implements xen memory mapping support via a separate feature
+`xen`, and this crate uses the same feature name to enable Xen support.
+
+Also, for xen mappings, the memory regions passed by the frontend contains few
+extra fields as described in the vhost-user protocol documentation.
+
+It was decided by the `rust-vmm` maintainers to keep the interface simple and
+build the crate for either standard Unix memory mapping or Xen, and not both.
+
 ## License
 
 This project is licensed under

crates/vhost-user-backend/src/handler.rs

@@ -22,7 +22,7 @@ use virtio_bindings::bindings::virtio_ring::VIRTIO_RING_F_EVENT_IDX;
 use virtio_queue::{Error as VirtQueError, QueueT};
 use vm_memory::bitmap::Bitmap;
 use vm_memory::mmap::NewBitmap;
-use vm_memory::{FileOffset, GuestAddress, GuestAddressSpace, GuestMemoryMmap, GuestRegionMmap};
+use vm_memory::{GuestAddress, GuestAddressSpace, GuestMemoryMmap, GuestRegionMmap};
 use vmm_sys_util::epoll::EventSet;
 
 use super::backend::VhostUserBackend;
@@ -277,23 +277,27 @@ where
     ) -> VhostUserResult<()> {
         // We need to create tuple of ranges from the list of VhostUserMemoryRegion
         // that we get from the caller.
-        let mut regions: Vec<(GuestAddress, usize, Option<FileOffset>)> = Vec::new();
+        let mut regions = Vec::new();
         let mut mappings: Vec<AddrMapping> = Vec::new();
 
         for (region, file) in ctx.iter().zip(files) {
-            let g_addr = GuestAddress(region.guest_phys_addr);
-            let len = region.memory_size as usize;
-            let f_off = FileOffset::new(file, region.mmap_offset);
-
-            regions.push((g_addr, len, Some(f_off)));
+            regions.push(
+                GuestRegionMmap::new(
+                    region.mmap_region(file)?,
+                    GuestAddress(region.guest_phys_addr),
+                )
+                .map_err(|e| {
+                    VhostUserError::ReqHandlerError(io::Error::new(io::ErrorKind::Other, e))
+                })?,
+            );
             mappings.push(AddrMapping {
                 vmm_addr: region.user_addr,
                 size: region.memory_size,
                 gpa_base: region.guest_phys_addr,
             });
         }
 
-        let mem = GuestMemoryMmap::from_ranges_with_files(regions).map_err(|e| {
+        let mem = GuestMemoryMmap::from_regions(regions).map_err(|e| {
             VhostUserError::ReqHandlerError(io::Error::new(io::ErrorKind::Other, e))
         })?;
 
@@ -526,10 +530,9 @@ where
         file: File,
     ) -> VhostUserResult<()> {
         let guest_region = Arc::new(
-            GuestRegionMmap::from_range(
+            GuestRegionMmap::new(
+                region.mmap_region(file)?,
                 GuestAddress(region.guest_phys_addr),
-                region.memory_size as usize,
-                Some(FileOffset::new(file, region.mmap_offset)),
             )
             .map_err(|e| {
                 VhostUserError::ReqHandlerError(io::Error::new(io::ErrorKind::Other, e))