# blk.rs - source
Source of the Rust file `/home/runner/.cargo/git/checkouts/virtio-drivers-4fdfaa862bcdc399/f30d426/src/blk.rs`.
Keywords: rust, rustlang, rust-lang

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    use super::*;
    use crate::header::VirtIOHeader;
    use crate::queue::VirtQueue;
    use bitflags::*;
    use core::hint::spin_loop;
    use log::*;
    use volatile::Volatile;

    /// The virtio block device is a simple virtual block device (ie. disk).
    ///
    /// Read and write requests (and other exotic requests) are placed in the queue,
    /// and serviced (probably out of order) by the device except where noted.
    pub struct VirtIOBlk<'a> {
        header: &'static mut VirtIOHeader,
        queue: VirtQueue<'a>,
        capacity: usize,
    }

    impl VirtIOBlk<'_> {
        /// Create a new VirtIO-Blk driver.
        pub fn new(header: &'static mut VirtIOHeader) -> Result<Self> {
            header.begin_init(|features| {
                let features = BlkFeature::from_bits_truncate(features);
                info!("device features: {:?}", features);
                // negotiate these flags only
                let supported_features = BlkFeature::empty();
                (features & supported_features).bits()
            });

            // read configuration space
            let config = unsafe { &mut *(header.config_space() as *mut BlkConfig) };
            info!("config: {:?}", config);
            info!(
                "found a block device of size {}KB",
                config.capacity.read() / 2
            );

            let queue = VirtQueue::new(header, 0, 16)?;
            header.finish_init();

            Ok(VirtIOBlk {
                header,
                queue,
                capacity: config.capacity.read() as usize,
            })
        }

        /// Acknowledge interrupt.
        pub fn ack_interrupt(&mut self) -> bool {
            self.header.ack_interrupt()
        }

        /// Read a block.
        pub fn read_block(&mut self, block_id: usize, buf: &mut [u8]) -> Result {
            assert_eq!(buf.len(), BLK_SIZE);
            let req = BlkReq {
                type_: ReqType::In,
                reserved: 0,
                sector: block_id as u64,
            };
            let mut resp = BlkResp::default();
            self.queue.add(&[req.as_buf()], &[buf, resp.as_buf_mut()])?;
            self.header.notify(0);
            while !self.queue.can_pop() {
                spin_loop();
            }
            self.queue.pop_used()?;
            match resp.status {
                RespStatus::Ok => Ok(()),
                _ => Err(Error::IoError),
            }
        }

        /// Read a block in a non-blocking way which means that it returns immediately.
        ///
        /// # Arguments
        ///
        /// * `block_id` - The identifier of the block to read.
        /// * `buf` - The buffer in the memory which the block is read into.
        /// * `resp` - A mutable reference to a variable provided by the caller
        ///   which contains the status of the requests. The caller can safely
        ///   read the variable only after the request is ready.
        ///
        /// # Usage
        ///
        /// It will submit request to the virtio block device and return a token identifying
        /// the position of the first Descriptor in the chain. If there are not enough
        /// Descriptors to allocate, then it returns [Error::BufferTooSmall].
        ///
        /// After the request is ready, `resp` will be updated and the caller can get the
        /// status of the request(e.g. succeed or failed) through it. However, the caller
        /// **must not** spin on `resp` to wait for it to change. A safe way is to read it
        /// after the same token as this method returns is fetched through [VirtIOBlk::pop_used()],
        /// which means that the request has been ready.
        ///
        /// # Safety
        ///
        /// `buf` is still borrowed by the underlying virtio block device even if this
        /// method returns. Thus, it is the caller's responsibility to guarantee that
        /// `buf` is not accessed before the request is completed in order to avoid
        /// data races.
        pub unsafe fn read_block_nb(
            &mut self,
            block_id: usize,
            buf: &mut [u8],
            resp: &mut BlkResp,
        ) -> Result<u16> {
            assert_eq!(buf.len(), BLK_SIZE);
            let req = BlkReq {
                type_: ReqType::In,
                reserved: 0,
                sector: block_id as u64,
            };
            let token = self.queue.add(&[req.as_buf()], &[buf, resp.as_buf_mut()])?;
            self.header.notify(0);
            Ok(token)
        }

        /// Write a block.
        pub fn write_block(&mut self, block_id: usize, buf: &[u8]) -> Result {
            assert_eq!(buf.len(), BLK_SIZE);
            let req = BlkReq {
                type_: ReqType::Out,
                reserved: 0,
                sector: block_id as u64,
            };
            let mut resp = BlkResp::default();
            self.queue.add(&[req.as_buf(), buf], &[resp.as_buf_mut()])?;
            self.header.notify(0);
            while !self.queue.can_pop() {
                spin_loop();
            }
            self.queue.pop_used()?;
            match resp.status {
                RespStatus::Ok => Ok(()),
                _ => Err(Error::IoError),
            }
        }

        //// Write a block in a non-blocking way which means that it returns immediately.
        ///
        /// # Arguments
        ///
        /// * `block_id` - The identifier of the block to write.
        /// * `buf` - The buffer in the memory containing the data to write to the block.
        /// * `resp` - A mutable reference to a variable provided by the caller
        ///   which contains the status of the requests. The caller can safely
        ///   read the variable only after the request is ready.
        ///
        /// # Usage
        ///
        /// See also [VirtIOBlk::read_block_nb()].
        ///
        /// # Safety
        ///
        /// See also [VirtIOBlk::read_block_nb()].
        pub unsafe fn write_block_nb(
            &mut self,
            block_id: usize,
            buf: &[u8],
            resp: &mut BlkResp,
        ) -> Result<u16> {
            assert_eq!(buf.len(), BLK_SIZE);
            let req = BlkReq {
                type_: ReqType::Out,
                reserved: 0,
                sector: block_id as u64,
            };
            let token = self.queue.add(&[req.as_buf(), buf], &[resp.as_buf_mut()])?;
            self.header.notify(0);
            Ok(token)
        }

        /// During an interrupt, it fetches a token of a completed request from the used
        /// ring and return it. If all completed requests have already been fetched, return
        /// Err(Error::NotReady).
        pub fn pop_used(&mut self) -> Result<u16> {
            self.queue.pop_used().map(|p| p.0)
        }

        /// Return size of its VirtQueue.
        /// It can be used to tell the caller how many channels he should monitor on.
        pub fn virt_queue_size(&self) -> u16 {
            self.queue.size()
        }
    }

    #[repr(C)]
    #[derive(Debug)]
    struct BlkConfig {
        /// Number of 512 Bytes sectors
        capacity: Volatile<u64>,
        size_max: Volatile<u32>,
        seg_max: Volatile<u32>,
        cylinders: Volatile<u16>,
        heads: Volatile<u8>,
        sectors: Volatile<u8>,
        blk_size: Volatile<u32>,
        physical_block_exp: Volatile<u8>,
        alignment_offset: Volatile<u8>,
        min_io_size: Volatile<u16>,
        opt_io_size: Volatile<u32>,
        // ... ignored
    }

    #[repr(C)]
    #[derive(Debug)]
    struct BlkReq {
        type_: ReqType,
        reserved: u32,
        sector: u64,
    }

    /// Response of a VirtIOBlk request.
    #[repr(C)]
    #[derive(Debug)]
    pub struct BlkResp {
        status: RespStatus,
    }

    impl BlkResp {
        /// Return the status of a VirtIOBlk request.
        pub fn status(&self) -> RespStatus {
            self.status
        }
    }

    #[repr(u32)]
    #[derive(Debug)]
    enum ReqType {
        In = 0,
        Out = 1,
        Flush = 4,
        Discard = 11,
        WriteZeroes = 13,
    }

    /// Status of a VirtIOBlk request.
    #[repr(u8)]
    #[derive(Debug, Eq, PartialEq, Copy, Clone)]
    pub enum RespStatus {
        /// Ok.
        Ok = 0,
        /// IoErr.
        IoErr = 1,
        /// Unsupported yet.
        Unsupported = 2,
        /// Not ready.
        _NotReady = 3,
    }

    impl Default for BlkResp {
        fn default() -> Self {
            BlkResp {
                status: RespStatus::_NotReady,
            }
        }
    }

    const BLK_SIZE: usize = 512;

    bitflags! {
        struct BlkFeature: u64 {
            /// Device supports request barriers. (legacy)
            const BARRIER       = 1 << 0;
            /// Maximum size of any single segment is in `size_max`.
            const SIZE_MAX      = 1 << 1;
            /// Maximum number of segments in a request is in `seg_max`.
            const SEG_MAX       = 1 << 2;
            /// Disk-style geometry specified in geometry.
            const GEOMETRY      = 1 << 4;
            /// Device is read-only.
            const RO            = 1 << 5;
            /// Block size of disk is in `blk_size`.
            const BLK_SIZE      = 1 << 6;
            /// Device supports scsi packet commands. (legacy)
            const SCSI          = 1 << 7;
            /// Cache flush command support.
            const FLUSH         = 1 << 9;
            /// Device exports information on optimal I/O alignment.
            const TOPOLOGY      = 1 << 10;
            /// Device can toggle its cache between writeback and writethrough modes.
            const CONFIG_WCE    = 1 << 11;
            /// Device can support discard command, maximum discard sectors size in
            /// `max_discard_sectors` and maximum discard segment number in
            /// `max_discard_seg`.
            const DISCARD       = 1 << 13;
            /// Device can support write zeroes command, maximum write zeroes sectors
            /// size in `max_write_zeroes_sectors` and maximum write zeroes segment
            /// number in `max_write_zeroes_seg`.
            const WRITE_ZEROES  = 1 << 14;

            // device independent
            const NOTIFY_ON_EMPTY       = 1 << 24; // legacy
            const ANY_LAYOUT            = 1 << 27; // legacy
            const RING_INDIRECT_DESC    = 1 << 28;
            const RING_EVENT_IDX        = 1 << 29;
            const UNUSED                = 1 << 30; // legacy
            const VERSION_1             = 1 << 32; // detect legacy

            // the following since virtio v1.1
            const ACCESS_PLATFORM       = 1 << 33;
            const RING_PACKED           = 1 << 34;
            const IN_ORDER              = 1 << 35;
            const ORDER_PLATFORM        = 1 << 36;
            const SR_IOV                = 1 << 37;
            const NOTIFICATION_DATA     = 1 << 38;
        }
    }

    unsafe impl AsBuf for BlkReq {}
    unsafe impl AsBuf for BlkResp {}