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devices: block: add support for read-only feature

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The virtio block specification defines the VIRTIO_BLK_F_RO feature bit
to indicate read-only block devices.  Plumb the read-only status of
block devices from the crosvm frontend into the virtio block device and
populate the flag when appropriate.

BUG=chromium:872973
TEST=Verify lsblk output in guest has the correct RO values

Change-Id: I23af87cce8020641cd702adca6e8ff9fdd2b8220
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1170306
Reviewed-by: Zach Reizner <zachr@chromium.org>
This commit is contained in:
Daniel Verkamp 2018-08-09 16:27:44 -07:00 committed by chrome-bot
parent 18fa20569f
commit 70589a0797
2 changed files with 24 additions and 8 deletions
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28
devices/src/virtio/block.rs
View file

@ -28,6 +28,7 @@ const VIRTIO_BLK_S_OK: u8 = 0;
const VIRTIO_BLK_S_IOERR: u8 = 1;
const VIRTIO_BLK_S_UNSUPP: u8 = 2;
const VIRTIO_BLK_F_RO: u32 = 5;
const VIRTIO_BLK_F_FLUSH: u32 = 9;
pub trait DiskFile: Read + Seek + Write {}
@ -345,6 +346,7 @@ pub struct Block<T: DiskFile> {
disk_image: Option<T>,
config_space: Vec<u8>,
avail_features: u64,
read_only: bool,
}
fn build_config_space(disk_size: u64) -> Vec<u8> {
@ -363,7 +365,7 @@ impl<T: DiskFile> Block<T> {
/// Create a new virtio block device that operates on the given file.
///
/// The given file must be seekable and sizable.
pub fn new(mut disk_image: T) -> SysResult<Block<T>> {
pub fn new(mut disk_image: T, read_only: bool) -> SysResult<Block<T>> {
let disk_size = disk_image.seek(SeekFrom::End(0))? as u64;
if disk_size % SECTOR_SIZE != 0 {
warn!("Disk size {} is not a multiple of sector size {}; \
@ -373,12 +375,16 @@ impl<T: DiskFile> Block<T> {
}
let mut avail_features: u64 = 1 << VIRTIO_BLK_F_FLUSH;
if read_only {
avail_features |= 1 << VIRTIO_BLK_F_RO;
}
Ok(Block {
kill_evt: None,
disk_image: Some(disk_image),
config_space: build_config_space(disk_size),
avail_features,
read_only,
})
}
}
@ -489,7 +495,7 @@ mod tests {
let f = File::create(&path).unwrap();
f.set_len(0x1000).unwrap();
let b = Block::new(f).unwrap();
let b = Block::new(f, true).unwrap();
let mut num_sectors = [0u8; 4];
b.read_config(0, &mut num_sectors);
// size is 0x1000, so num_sectors is 8 (4096/512).
@ -506,10 +512,20 @@ mod tests {
let mut path = PathBuf::from(tempdir.as_path().unwrap());
path.push("disk_image");
let f = File::create(&path).unwrap();
let b = Block::new(f).unwrap();
// read-write block device
{
let f = File::create(&path).unwrap();
let b = Block::new(f, false).unwrap();
// writable device should just set VIRTIO_BLK_F_FLUSH
assert_eq!(0x200, b.features(0));
}
// VIRTIO_BLK_F_FLUSH should always be set
assert_eq!(0x200, b.features(0));
// read-only block device
{
let f = File::create(&path).unwrap();
let b = Block::new(f, true).unwrap();
// read-only device should set VIRTIO_BLK_F_FLUSH and VIRTIO_BLK_F_RO
assert_eq!(0x220, b.features(0));
}
}
}

4
src/linux.rs
View file

@ -419,13 +419,13 @@ fn setup_mmio_bus(cfg: &Config,
let block_box: Box<devices::virtio::VirtioDevice> = match disk.disk_type {
DiskType::FlatFile => { // Access as a raw block device.
Box::new(devices::virtio::Block::new(raw_image)
Box::new(devices::virtio::Block::new(raw_image, disk.read_only)
.map_err(|e| Error::BlockDeviceNew(e))?)
}
DiskType::Qcow => { // Valid qcow header present
let qcow_image = QcowFile::from(raw_image)
.map_err(|e| Error::QcowDeviceCreate(e))?;
Box::new(devices::virtio::Block::new(qcow_image)
Box::new(devices::virtio::Block::new(qcow_image, disk.read_only)
.map_err(|e| Error::BlockDeviceNew(e))?)
}
};