virtio-devices: mem: Accept handlers to update DMA mappings

Create two functions for registering/unregistering DMA mapping handlers,
each handler being associated with a VFIO device.

Whenever the plugged_size is modified (which means triggered by the
virtio-mem driver in the guest), the virtio-mem backend is responsible
for updating the DMA mappings related to every VFIO device through the
handler previously provided.

It's important to update the map when the handler is either registered
or unregistered as well, as we don't want to miss some plugged memory
that would have been added before the VFIO device is added to the VM.

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

virtio-devices/src/mem.rs

@@ -24,6 +24,7 @@ use crate::{VirtioInterrupt, VirtioInterruptType};
 use anyhow::anyhow;
 use libc::EFD_NONBLOCK;
 use seccomp::{SeccompAction, SeccompFilter};
+use std::collections::BTreeMap;
 use std::io;
 use std::mem::size_of;
 use std::os::unix::io::{AsRawFd, RawFd};
@@ -32,6 +33,7 @@ use std::sync::atomic::{AtomicBool, AtomicU64, Ordering};
 use std::sync::mpsc;
 use std::sync::{Arc, Barrier, Mutex};
 use std::thread;
+use vm_device::dma_mapping::ExternalDmaMapping;
 use vm_memory::{
     Address, ByteValued, Bytes, GuestAddress, GuestAddressSpace, GuestMemoryAtomic,
     GuestMemoryError, GuestMemoryMmap, GuestMemoryRegion, GuestRegionMmap,
@@ -124,6 +126,12 @@ pub enum Error {
     ValidateError(anyhow::Error),
     // Failed discarding memory range
     DiscardMemoryRange(std::io::Error),
+    // Failed DMA mapping.
+    DmaMap(std::io::Error),
+    // Failed DMA unmapping.
+    DmaUnmap(std::io::Error),
+    // Invalid DMA mapping handler
+    InvalidDmaMappingHandler,
 }
 
 #[repr(C)]
@@ -401,12 +409,16 @@ impl BlocksState {
             *state = plug;
         }
     }
+
+    fn inner(&self) -> &Vec<bool> {
+        &self.0
+    }
 }
 
 struct MemEpollHandler {
     host_addr: u64,
     host_fd: Option<RawFd>,
-    blocks_state: BlocksState,
+    blocks_state: Arc<Mutex<BlocksState>>,
     config: Arc<Mutex<VirtioMemConfig>>,
     resize: ResizeSender,
     queue: Queue,
@@ -416,6 +428,7 @@ struct MemEpollHandler {
     kill_evt: EventFd,
     pause_evt: EventFd,
     hugepages: bool,
+    dma_mapping_handlers: Arc<Mutex<BTreeMap<u32, Arc<dyn ExternalDmaMapping>>>>,
 }
 
 impl MemEpollHandler {
@@ -473,6 +486,8 @@ impl MemEpollHandler {
         let first_block_index = (offset / config.block_size) as usize;
         if !self
             .blocks_state
+            .lock()
+            .unwrap()
             .is_range_state(first_block_index, nb_blocks, !plug)
         {
             return VIRTIO_MEM_RESP_ERROR;
@@ -486,11 +501,40 @@ impl MemEpollHandler {
         }
 
         self.blocks_state
+            .lock()
+            .unwrap()
             .set_range(first_block_index, nb_blocks, plug);
 
         if plug {
+            let handlers = self.dma_mapping_handlers.lock().unwrap();
+            let mut gpa = addr;
+            for _ in 0..nb_blocks {
+                for (_, handler) in handlers.iter() {
+                    if let Err(e) = handler.map(gpa, gpa, config.block_size) {
+                        error!(
+                            "failed DMA mapping addr 0x{:x} size 0x{:x}: {}",
+                            gpa, config.block_size, e
+                        );
+                        return VIRTIO_MEM_RESP_ERROR;
+                    }
+                }
+
+                gpa += config.block_size;
+            }
+
             config.plugged_size += size;
         } else {
+            let handlers = self.dma_mapping_handlers.lock().unwrap();
+            for (_, handler) in handlers.iter() {
+                if let Err(e) = handler.unmap(addr, size) {
+                    error!(
+                        "failed DMA unmapping addr 0x{:x} size 0x{:x}: {}",
+                        addr, size, e
+                    );
+                    return VIRTIO_MEM_RESP_ERROR;
+                }
+            }
+
             config.plugged_size -= size;
         }
 
@@ -504,8 +548,30 @@ impl MemEpollHandler {
             return VIRTIO_MEM_RESP_ERROR;
         }
 
-        self.blocks_state
-            .set_range(0, (config.region_size / config.block_size) as u16, false);
+        // Remaining plugged blocks are unmapped.
+        if config.plugged_size > 0 {
+            let handlers = self.dma_mapping_handlers.lock().unwrap();
+            for (idx, plugged) in self.blocks_state.lock().unwrap().inner().iter().enumerate() {
+                if *plugged {
+                    let gpa = config.addr + (idx as u64 * config.block_size);
+                    for (_, handler) in handlers.iter() {
+                        if let Err(e) = handler.unmap(gpa, config.block_size) {
+                            error!(
+                                "failed DMA unmapping addr 0x{:x} size 0x{:x}: {}",
+                                gpa, config.block_size, e
+                            );
+                            return VIRTIO_MEM_RESP_ERROR;
+                        }
+                    }
+                }
+            }
+        }
+
+        self.blocks_state.lock().unwrap().set_range(
+            0,
+            (config.region_size / config.block_size) as u16,
+            false,
+        );
 
         config.plugged_size = 0;
 
@@ -524,19 +590,23 @@ impl MemEpollHandler {
 
         let offset = addr - config.addr;
         let first_block_index = (offset / config.block_size) as usize;
-        let resp_state = if self
-            .blocks_state
-            .is_range_state(first_block_index, nb_blocks, true)
-        {
-            VIRTIO_MEM_STATE_PLUGGED
-        } else if self
-            .blocks_state
-            .is_range_state(first_block_index, nb_blocks, false)
-        {
-            VIRTIO_MEM_STATE_UNPLUGGED
-        } else {
-            VIRTIO_MEM_STATE_MIXED
-        };
+        let resp_state =
+            if self
+                .blocks_state
+                .lock()
+                .unwrap()
+                .is_range_state(first_block_index, nb_blocks, true)
+            {
+                VIRTIO_MEM_STATE_PLUGGED
+            } else if self.blocks_state.lock().unwrap().is_range_state(
+                first_block_index,
+                nb_blocks,
+                false,
+            ) {
+                VIRTIO_MEM_STATE_UNPLUGGED
+            } else {
+                VIRTIO_MEM_STATE_MIXED
+            };
 
         (resp_type, resp_state)
     }
@@ -675,6 +745,8 @@ pub struct Mem {
     config: Arc<Mutex<VirtioMemConfig>>,
     seccomp_action: SeccompAction,
     hugepages: bool,
+    dma_mapping_handlers: Arc<Mutex<BTreeMap<u32, Arc<dyn ExternalDmaMapping>>>>,
+    blocks_state: Arc<Mutex<BlocksState>>,
 }
 
 impl Mem {
@@ -758,8 +830,64 @@ impl Mem {
             config: Arc::new(Mutex::new(config)),
             seccomp_action,
             hugepages,
+            dma_mapping_handlers: Arc::new(Mutex::new(BTreeMap::new())),
+            blocks_state: Arc::new(Mutex::new(BlocksState(vec![
+                false;
+                (config.region_size / config.block_size)
+                    as usize
+            ]))),
         })
     }
+
+    pub fn add_dma_mapping_handler(
+        &mut self,
+        device_id: u32,
+        handler: Arc<dyn ExternalDmaMapping>,
+    ) -> result::Result<(), Error> {
+        let config = self.config.lock().unwrap();
+
+        if config.plugged_size > 0 {
+            for (idx, plugged) in self.blocks_state.lock().unwrap().inner().iter().enumerate() {
+                if *plugged {
+                    let gpa = config.addr + (idx as u64 * config.block_size);
+                    handler
+                        .map(gpa, gpa, config.block_size)
+                        .map_err(Error::DmaMap)?;
+                }
+            }
+        }
+
+        self.dma_mapping_handlers
+            .lock()
+            .unwrap()
+            .insert(device_id, handler);
+
+        Ok(())
+    }
+
+    pub fn remove_dma_mapping_handler(&mut self, device_id: u32) -> result::Result<(), Error> {
+        let handler = self
+            .dma_mapping_handlers
+            .lock()
+            .unwrap()
+            .remove(&device_id)
+            .ok_or(Error::InvalidDmaMappingHandler)?;
+
+        let config = self.config.lock().unwrap();
+
+        if config.plugged_size > 0 {
+            for (idx, plugged) in self.blocks_state.lock().unwrap().inner().iter().enumerate() {
+                if *plugged {
+                    let gpa = config.addr + (idx as u64 * config.block_size);
+                    handler
+                        .unmap(gpa, config.block_size)
+                        .map_err(Error::DmaUnmap)?;
+                }
+            }
+        }
+
+        Ok(())
+    }
 }
 
 impl Drop for Mem {
@@ -825,10 +953,7 @@ impl VirtioDevice for Mem {
         let mut handler = MemEpollHandler {
             host_addr: self.host_addr,
             host_fd: self.host_fd,
-            blocks_state: BlocksState(vec![
-                false;
-                (config.region_size / config.block_size) as usize
-            ]),
+            blocks_state: Arc::clone(&self.blocks_state),
             config: self.config.clone(),
             resize: self.resize.clone(),
             queue: queues.remove(0),
@@ -838,6 +963,7 @@ impl VirtioDevice for Mem {
             kill_evt,
             pause_evt,
             hugepages: self.hugepages,
+            dma_mapping_handlers: Arc::clone(&self.dma_mapping_handlers),
         };
 
         handler

virtio-devices/src/seccomp_filters.rs

@@ -55,6 +55,24 @@ const SYS_IO_URING_ENTER: i64 = 426;
 // See include/uapi/asm-generic/ioctls.h in the kernel code.
 const FIONBIO: u64 = 0x5421;
 
+// See include/uapi/linux/vfio.h in the kernel code.
+const VFIO_IOMMU_MAP_DMA: u64 = 0x3b71;
+const VFIO_IOMMU_UNMAP_DMA: u64 = 0x3b72;
+
+fn create_virtio_iommu_ioctl_seccomp_rule() -> Vec<SeccompRule> {
+    or![
+        and![Cond::new(1, ArgLen::DWORD, Eq, VFIO_IOMMU_MAP_DMA).unwrap()],
+        and![Cond::new(1, ArgLen::DWORD, Eq, VFIO_IOMMU_UNMAP_DMA).unwrap()],
+    ]
+}
+
+fn create_virtio_mem_ioctl_seccomp_rule() -> Vec<SeccompRule> {
+    or![
+        and![Cond::new(1, ArgLen::DWORD, Eq, VFIO_IOMMU_MAP_DMA).unwrap()],
+        and![Cond::new(1, ArgLen::DWORD, Eq, VFIO_IOMMU_UNMAP_DMA).unwrap()],
+    ]
+}
+
 fn virtio_balloon_thread_rules() -> Vec<SyscallRuleSet> {
     vec![
         allow_syscall(libc::SYS_brk),
@@ -156,6 +174,7 @@ fn virtio_iommu_thread_rules() -> Vec<SyscallRuleSet> {
         allow_syscall(libc::SYS_epoll_wait),
         allow_syscall(libc::SYS_exit),
         allow_syscall(libc::SYS_futex),
+        allow_syscall_if(libc::SYS_ioctl, create_virtio_iommu_ioctl_seccomp_rule()),
         allow_syscall(libc::SYS_madvise),
         allow_syscall(libc::SYS_mmap),
         allow_syscall(libc::SYS_mprotect),
@@ -179,6 +198,7 @@ fn virtio_mem_thread_rules() -> Vec<SyscallRuleSet> {
         allow_syscall(libc::SYS_exit),
         allow_syscall(libc::SYS_fallocate),
         allow_syscall(libc::SYS_futex),
+        allow_syscall_if(libc::SYS_ioctl, create_virtio_mem_ioctl_seccomp_rule()),
         allow_syscall(libc::SYS_madvise),
         allow_syscall(libc::SYS_munmap),
         allow_syscall(libc::SYS_read),