vmm: hypervisor: split set_user_memory_region to two functions

Previously the same function was used to both create and remove regions.
This worked on KVM because it uses size 0 to indicate removal.

MSHV has two calls -- one for creation and one for removal. It also
requires having the size field available because it is not slot based.

Split set_user_memory_region to {create/remove}_user_memory_region. For
KVM they still use set_user_memory_region underneath, but for MSHV they
map to different functions.

This fixes user memory region removal on MSHV.

Signed-off-by: Wei Liu <liuwe@microsoft.com>

hypervisor/src/kvm/mod.rs

@@ -234,7 +234,7 @@ impl vm::Vm for KvmVm {
             .map_err(|e| vm::HypervisorVmError::SetGsiRouting(e.into()))
     }
     ///
-    /// Creates a memory region structure that can be used with set_user_memory_region
+    /// Creates a memory region structure that can be used with {create/remove}_user_memory_region
     ///
     fn make_user_memory_region(
         &self,
@@ -259,14 +259,29 @@ impl vm::Vm for KvmVm {
         }
     }
     ///
-    /// Creates/modifies a guest physical memory slot.
+    /// Creates a guest physical memory region.
     ///
-    fn set_user_memory_region(&self, user_memory_region: MemoryRegion) -> vm::Result<()> {
+    fn create_user_memory_region(&self, user_memory_region: MemoryRegion) -> vm::Result<()> {
         // Safe because guest regions are guaranteed not to overlap.
         unsafe {
             self.fd
                 .set_user_memory_region(user_memory_region)
-                .map_err(|e| vm::HypervisorVmError::SetUserMemory(e.into()))
+                .map_err(|e| vm::HypervisorVmError::CreateUserMemory(e.into()))
+        }
+    }
+    ///
+    /// Removes a guest physical memory region.
+    ///
+    fn remove_user_memory_region(&self, user_memory_region: MemoryRegion) -> vm::Result<()> {
+        let mut region = user_memory_region;
+
+        // Setting the size to 0 means "remove"
+        region.memory_size = 0;
+        // Safe because guest regions are guaranteed not to overlap.
+        unsafe {
+            self.fd
+                .set_user_memory_region(region)
+                .map_err(|e| vm::HypervisorVmError::RemoveUserMemory(e.into()))
         }
     }
     ///

hypervisor/src/mshv/mod.rs

@@ -798,11 +798,19 @@ impl vm::Vm for MshvVm {
             .map_err(|e| vm::HypervisorVmError::UnregisterIoEvent(e.into()))
     }
 
-    /// Creates/modifies a guest physical memory slot.
-    fn set_user_memory_region(&self, user_memory_region: MemoryRegion) -> vm::Result<()> {
+    /// Creates a guest physical memory region.
+    fn create_user_memory_region(&self, user_memory_region: MemoryRegion) -> vm::Result<()> {
         self.fd
             .map_user_memory(user_memory_region)
-            .map_err(|e| vm::HypervisorVmError::SetUserMemory(e.into()))?;
+            .map_err(|e| vm::HypervisorVmError::CreateUserMemory(e.into()))?;
+        Ok(())
+    }
+
+    /// Removes a guest physical memory region.
+    fn remove_user_memory_region(&self, user_memory_region: MemoryRegion) -> vm::Result<()> {
+        self.fd
+            .unmap_user_memory(user_memory_region)
+            .map_err(|e| vm::HypervisorVmError::RemoveUserMemory(e.into()))?;
         Ok(())
     }
 

hypervisor/src/vm.rs

@@ -92,10 +92,15 @@ pub enum HypervisorVmError {
     #[error("Failed to set GSI routing: {0}")]
     SetGsiRouting(#[source] anyhow::Error),
     ///
-    /// Set user memory error
+    /// Create user memory error
     ///
-    #[error("Failed to set user memory: {0}")]
-    SetUserMemory(#[source] anyhow::Error),
+    #[error("Failed to create user memory: {0}")]
+    CreateUserMemory(#[source] anyhow::Error),
+    ///
+    /// Remove user memory region error
+    ///
+    #[error("Failed to remove user memory: {0}")]
+    RemoveUserMemory(#[source] anyhow::Error),
     ///
     /// Create device error
     ///
@@ -218,7 +223,7 @@ pub trait Vm: Send + Sync {
     fn unregister_ioevent(&self, fd: &EventFd, addr: &IoEventAddress) -> Result<()>;
     /// Sets the GSI routing table entries, overwriting any previously set
     fn set_gsi_routing(&self, entries: &[IrqRoutingEntry]) -> Result<()>;
-    /// Creates a memory region structure that can be used with set_user_memory_region
+    /// Creates a memory region structure that can be used with {create/remove}_user_memory_region
     fn make_user_memory_region(
         &self,
         slot: u32,
@@ -228,8 +233,10 @@ pub trait Vm: Send + Sync {
         readonly: bool,
         log_dirty_pages: bool,
     ) -> MemoryRegion;
-    /// Creates/modifies a guest physical memory slot.
-    fn set_user_memory_region(&self, user_memory_region: MemoryRegion) -> Result<()>;
+    /// Creates a guest physical memory slot.
+    fn create_user_memory_region(&self, user_memory_region: MemoryRegion) -> Result<()>;
+    /// Removes a guest physical memory slot.
+    fn remove_user_memory_region(&self, user_memory_region: MemoryRegion) -> Result<()>;
     #[cfg(feature = "kvm")]
     /// Creates an emulated device in the kernel.
     fn create_device(&self, device: &mut CreateDevice) -> Result<Arc<dyn Device>>;