feat(vfio): support device p2p DMA by dma-buf fd

alioth/src/board/board.rs

@@ -20,6 +20,7 @@ mod aarch64;
 mod x86_64;
 
 use std::ffi::CStr;
+use std::os::fd::BorrowedFd;
 use std::sync::Arc;
 
 use libc::{MAP_PRIVATE, MAP_SHARED};
@@ -187,11 +188,21 @@ where
         Ok(())
     }
 
-    fn dev_mem_added(&self, gpa: u64, pages: &ArcMemPages) -> mem::Result<()> {
+    fn dev_mem_added(
+        &self,
+        gpa: u64,
+        pages: &ArcMemPages,
+        _: Option<BorrowedFd>,
+    ) -> mem::Result<()> {
         self.ram_added(gpa, pages)
     }
 
-    fn dev_mem_removed(&self, gpa: u64, pages: &ArcMemPages) -> mem::Result<()> {
+    fn dev_mem_removed(
+        &self,
+        gpa: u64,
+        pages: &ArcMemPages,
+        _: Option<BorrowedFd>,
+    ) -> mem::Result<()> {
         self.ram_removed(gpa, pages)
     }
 }

alioth/src/board/board_amd64/sev.rs

@@ -14,6 +14,7 @@
 
 use std::arch::x86_64::{__cpuid, CpuidResult};
 use std::collections::HashMap;
+use std::os::fd::BorrowedFd;
 use std::sync::Arc;
 
 use crate::arch::cpuid::{
@@ -149,11 +150,11 @@ where
         Ok(())
     }
 
-    fn dev_mem_added(&self, _: u64, _: &ArcMemPages) -> mem::Result<()> {
+    fn dev_mem_added(&self, _: u64, _: &ArcMemPages, _: Option<BorrowedFd>) -> mem::Result<()> {
         Ok(())
     }
 
-    fn dev_mem_removed(&self, _: u64, _: &ArcMemPages) -> mem::Result<()> {
+    fn dev_mem_removed(&self, _: u64, _: &ArcMemPages, _: Option<BorrowedFd>) -> mem::Result<()> {
         Ok(())
     }
 }

alioth/src/mem/mem.rs

@@ -18,6 +18,7 @@ pub mod mapped;
 
 use std::any::{Any, type_name};
 use std::fmt::Debug;
+use std::os::fd::{AsFd, BorrowedFd, OwnedFd};
 use std::sync::Arc;
 
 use parking_lot::{Mutex, RwLock};
@@ -124,15 +125,18 @@ impl MemSpec {
 #[derive(Debug)]
 pub enum MemRange {
     Ram(ArcMemPages),
-    DevMem(ArcMemPages),
+    DevMem {
+        pages: ArcMemPages,
+        dma_buf: Option<OwnedFd>,
+    },
     Emulated(Arc<dyn Mmio>),
     Span(u64),
 }
 
 impl MemRange {
     pub fn size(&self) -> u64 {
         match self {
-            MemRange::Ram(pages) | MemRange::DevMem(pages) => pages.size(),
+            MemRange::Ram(pages) | MemRange::DevMem { pages, .. } => pages.size(),
             MemRange::Emulated(range) => Mmio::size(range),
             MemRange::Span(size) => *size,
         }
@@ -186,7 +190,10 @@ impl MemRegion {
     pub fn with_dev_mem(pages: ArcMemPages, type_: MemRegionType) -> MemRegion {
         let size = pages.size();
         MemRegion {
-            ranges: vec![MemRange::DevMem(pages)],
+            ranges: vec![MemRange::DevMem {
+                pages,
+                dma_buf: None,
+            }],
             entries: vec![MemRegionEntry { type_, size }],
             callbacks: Mutex::new(vec![]),
         }
@@ -245,8 +252,8 @@ impl SlotBackend for Arc<IoRegion> {
 pub trait LayoutChanged: Debug + Send + Sync + 'static {
     fn ram_added(&self, gpa: u64, pages: &ArcMemPages) -> Result<()>;
     fn ram_removed(&self, gpa: u64, pages: &ArcMemPages) -> Result<()>;
-    fn dev_mem_added(&self, gpa: u64, pages: &ArcMemPages) -> Result<()>;
-    fn dev_mem_removed(&self, gpa: u64, pages: &ArcMemPages) -> Result<()>;
+    fn dev_mem_added(&self, gpa: u64, pages: &ArcMemPages, fd: Option<BorrowedFd>) -> Result<()>;
+    fn dev_mem_removed(&self, gpa: u64, pages: &ArcMemPages, fd: Option<BorrowedFd>) -> Result<()>;
 }
 
 pub trait LayoutUpdated: Debug + Send + Sync + 'static {
@@ -285,7 +292,10 @@ impl Memory {
                 let gpa = addr + offset;
                 match range {
                     MemRange::Ram(r) => callback.ram_added(gpa, r)?,
-                    MemRange::Span(_) | MemRange::Emulated(_) | MemRange::DevMem(_) => {}
+                    MemRange::DevMem { pages, dma_buf } => {
+                        callback.dev_mem_added(gpa, pages, dma_buf.as_ref().map(AsFd::as_fd))?
+                    }
+                    MemRange::Span(_) | MemRange::Emulated(_) => {}
                 }
                 offset += range.size();
             }
@@ -327,8 +337,8 @@ impl Memory {
         let mut ram_updated = false;
         for range in &region.ranges {
             let gpa = addr + offset;
-            if let MemRange::Ram(r) | MemRange::DevMem(r) = range {
-                self.ram_bus.add(gpa, r.clone())?;
+            if let MemRange::Ram(pages) | MemRange::DevMem { pages, .. } = range {
+                self.ram_bus.add(gpa, pages.clone())?;
                 ram_updated = true;
             }
             match range {
@@ -341,9 +351,9 @@ impl Memory {
                         callback.ram_added(gpa, r)?;
                     }
                 }
-                MemRange::DevMem(r) => {
+                MemRange::DevMem { pages: r, dma_buf } => {
                     for callback in &callbacks.changed {
-                        callback.dev_mem_added(gpa, r)?;
+                        callback.dev_mem_added(gpa, r, dma_buf.as_ref().map(AsFd::as_fd))?;
                     }
                 }
                 MemRange::Span(_) => {}
@@ -369,7 +379,7 @@ impl Memory {
         let mut ram_updated = false;
         for range in &region.ranges {
             let gpa = addr + offset;
-            if let MemRange::Ram(_) | MemRange::DevMem(_) = range {
+            if let MemRange::Ram(_) | MemRange::DevMem { .. } = range {
                 self.ram_bus.remove(gpa)?;
                 ram_updated = true;
             }
@@ -383,9 +393,9 @@ impl Memory {
                         callback.ram_removed(gpa, r)?;
                     }
                 }
-                MemRange::DevMem(r) => {
+                MemRange::DevMem { pages, dma_buf } => {
                     for callback in callbacks.changed.iter().rev() {
-                        callback.dev_mem_removed(gpa, r)?;
+                        callback.dev_mem_removed(gpa, pages, dma_buf.as_ref().map(AsFd::as_fd))?;
                     }
                 }
                 MemRange::Span(_) => {}
@@ -511,11 +521,11 @@ impl Memory {
         'out: while let Some((mut addr, region)) = regions.search_next(start) {
             let next_start = addr + region.size();
             for range in &region.ranges {
-                let (MemRange::DevMem(r) | MemRange::Ram(r)) = range else {
+                let (MemRange::DevMem { pages, .. } | MemRange::Ram(pages)) = range else {
                     addr += range.size();
                     continue;
                 };
-                let range_end = addr + r.size();
+                let range_end = addr + pages.size();
                 if range_end <= start {
                     addr = range_end;
                     continue;
@@ -602,11 +612,11 @@ where
         Ok(())
     }
 
-    fn dev_mem_added(&self, _: u64, _: &ArcMemPages) -> Result<()> {
+    fn dev_mem_added(&self, _: u64, _: &ArcMemPages, _: Option<BorrowedFd>) -> Result<()> {
         Ok(())
     }
 
-    fn dev_mem_removed(&self, _: u64, _: &ArcMemPages) -> Result<()> {
+    fn dev_mem_removed(&self, _: u64, _: &ArcMemPages, _: Option<BorrowedFd>) -> Result<()> {
         Ok(())
     }
 }

alioth/src/sys/linux/ioctl.rs

@@ -80,9 +80,9 @@ macro_rules! ioctl_write_val {
 
 #[macro_export]
 macro_rules! ioctl_write_ptr {
-    ($name:ident, $code:expr, $ty:ty) => {
+    ($name:ident, $code:expr, $ty:ty, $($g:ident),*) => {
         #[allow(clippy::missing_safety_doc)]
-        pub unsafe fn $name<F: ::std::os::fd::AsFd>(
+        pub unsafe fn $name<F: ::std::os::fd::AsFd, $($g),*>(
             fd: &F,
             val: &$ty,
         ) -> ::std::io::Result<libc::c_int> {
@@ -96,6 +96,9 @@ macro_rules! ioctl_write_ptr {
             })
         }
     };
+    ($name:ident, $code:expr, $ty:ty) => {
+        $crate::ioctl_write_ptr!($name, $code, $ty, );
+    };
     ($name:ident, $type_:expr, $nr:expr, $ty:ty) => {
         $crate::ioctl_write_ptr!(
             $name,

alioth/src/sys/linux/iommufd.rs

@@ -0,0 +1,36 @@
+// Copyright 2026 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use crate::ioctl_write_ptr;
+use crate::sys::ioctl::ioctl_io;
+use crate::sys::vfio::IommuIoasMapFlag;
+
+pub const IOMMUFD_TYPE: u8 = b';';
+
+#[repr(C)]
+pub struct IommuIoasMapFile {
+    pub size: u32,
+    pub flags: IommuIoasMapFlag,
+    pub ioas_id: u32,
+    pub fd: i32,
+    pub start: u64,
+    pub length: u64,
+    pub iova: u64,
+}
+
+ioctl_write_ptr! {
+    iommu_ioas_map_file,
+    ioctl_io(IOMMUFD_TYPE, 0x8f),
+    IommuIoasMapFile
+}

alioth/src/sys/linux/linux.rs

@@ -14,6 +14,7 @@
 
 pub mod if_tun;
 pub mod ioctl;
+pub mod iommufd;
 pub mod kvm;
 pub mod sev;
 pub mod tdx;

alioth/src/sys/linux/vfio.rs

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+use bitfield::bitfield;
+
 use crate::sys::ioctl::ioctl_io;
 use crate::{
     bitflags, consts, ioctl_none, ioctl_write_buf, ioctl_write_ptr, ioctl_write_val,
@@ -262,6 +264,48 @@ consts! {
     }
 }
 
+consts! {
+    pub struct DeviceFeature(u16) {
+        DMA_BUF = 11;
+    }
+}
+
+#[derive(Debug, Clone)]
+#[repr(C)]
+pub struct VfioRegionDmaRange {
+    pub offset: u64,
+    pub length: u64,
+}
+
+#[derive(Debug, Clone)]
+#[repr(C)]
+pub struct VfioDeviceFeatureDmaBuf<const N: usize> {
+    pub region_index: u32,
+    pub open_flags: u32,
+    pub flags: u32,
+    pub nr_ranges: u32,
+    pub dma_ranges: [VfioRegionDmaRange; N],
+}
+
+bitfield! {
+    #[derive(Copy, Clone, Default, PartialEq, Eq, Hash)]
+    pub struct VfioDeviceFeatureFlag(u32);
+    impl Debug;
+    impl new;
+    pub u16, from into DeviceFeature, index, set_index: 15, 0;
+    pub get, set_get: 16;
+    pub set, set_set: 17;
+    pub probe, set_probe: 18;
+}
+
+#[repr(C)]
+#[derive(Debug, Clone)]
+pub struct VfioDeviceFeature<T> {
+    pub argsz: u32,
+    pub flags: VfioDeviceFeatureFlag,
+    pub data: T,
+}
+
 ioctl_writeread!(
     vfio_device_get_info,
     ioctl_io(VFIO_TYPE, 107),
@@ -282,6 +326,13 @@ ioctl_write_buf!(vfio_device_set_irqs, ioctl_io(VFIO_TYPE, 110), VfioIrqSet);
 
 ioctl_none!(vfio_device_reset, VFIO_TYPE, 111);
 
+ioctl_write_ptr!(
+    vfio_device_feature,
+    ioctl_io(VFIO_TYPE, 117),
+    VfioDeviceFeature<T>,
+    T
+);
+
 ioctl_write_ptr!(
     vfio_device_bind_iommufd,
     ioctl_io(VFIO_TYPE, 118),

alioth/src/vfio/container.rs

@@ -13,7 +13,7 @@
 // limitations under the License.
 
 use std::fs::File;
-use std::os::fd::AsRawFd;
+use std::os::fd::{AsRawFd, BorrowedFd};
 use std::path::Path;
 use std::sync::Arc;
 
@@ -120,11 +120,21 @@ impl LayoutChanged for UpdateContainerMapping {
         Ok(())
     }
 
-    fn dev_mem_added(&self, gpa: u64, pages: &ArcMemPages) -> mem::Result<()> {
+    fn dev_mem_added(
+        &self,
+        gpa: u64,
+        pages: &ArcMemPages,
+        _: Option<BorrowedFd>,
+    ) -> mem::Result<()> {
         self.ram_added(gpa, pages)
     }
 
-    fn dev_mem_removed(&self, gpa: u64, pages: &ArcMemPages) -> mem::Result<()> {
+    fn dev_mem_removed(
+        &self,
+        gpa: u64,
+        pages: &ArcMemPages,
+        _: Option<BorrowedFd>,
+    ) -> mem::Result<()> {
         self.ram_removed(gpa, pages)
     }
 }