# qemu.rs - source
Source of the Rust file `src/boards/qemu.rs`.
Keywords: rust, rustlang, rust-lang

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    pub const CLOCK_FREQ: usize = 12500000;

    pub const MMIO: &[(usize, usize)] = &[
        (0x1000_0000, 0x1000),    // VIRT_UART0 in virt machine
        (0x1000_1000, 0x1000),    // VIRT_VIRTIO in virt machine
        (0x0C00_0000, 0x40_0000), // VIRT_PLIC in virt machine
        (0x0010_0000, 0x00_2000), // VIRT_TEST/RTC  in virt machine
    ];

    pub type BlockDeviceImpl = crate::drivers::block::VirtIOBlock;
    pub type CharDeviceImpl = crate::drivers::chardev::NS16550a<VIRT_UART>;

    pub const VIRT_PLIC: usize = 0xC00_0000;
    pub const VIRT_UART: usize = 0x1000_0000;

    use crate::drivers::block::BLOCK_DEVICE;
    use crate::drivers::chardev::{CharDevice, UART};
    use crate::drivers::plic::{IntrTargetPriority, PLIC};

    pub fn device_init() {
        use riscv::register::sie;
        let mut plic = unsafe { PLIC::new(VIRT_PLIC) };
        let hart_id: usize = 0;
        let supervisor = IntrTargetPriority::Supervisor;
        let machine = IntrTargetPriority::Machine;
        plic.set_threshold(hart_id, supervisor, 0);
        plic.set_threshold(hart_id, machine, 1);
        for intr_src_id in [1usize, 10] {
            plic.enable(hart_id, supervisor, intr_src_id);
            plic.set_priority(intr_src_id, 1);
        }
        unsafe {
            sie::set_sext();
        }
    }

    pub fn irq_handler() {
        let mut plic = unsafe { PLIC::new(VIRT_PLIC) };
        let intr_src_id = plic.claim(0, IntrTargetPriority::Supervisor);
        match intr_src_id {
            1 => BLOCK_DEVICE.handle_irq(),
            10 => UART.handle_irq(),
            _ => panic!("unsupported IRQ {}", intr_src_id),
        }
        plic.complete(0, IntrTargetPriority::Supervisor, intr_src_id);
    }

    //ref:: https://github.com/andre-richter/qemu-exit
    use core::arch::asm;

    const EXIT_SUCCESS: u32 = 0x5555; // Equals `exit(0)`. qemu successful exit

    const EXIT_FAILURE_FLAG: u32 = 0x3333;
    const EXIT_FAILURE: u32 = exit_code_encode(1); // Equals `exit(1)`. qemu failed exit
    const EXIT_RESET: u32 = 0x7777; // qemu reset

    pub trait QEMUExit {
        /// Exit with specified return code.
        ///
        /// Note: For `X86`, code is binary-OR'ed with `0x1` inside QEMU.
        fn exit(&self, code: u32) -> !;

        /// Exit QEMU using `EXIT_SUCCESS`, aka `0`, if possible.
        ///
        /// Note: Not possible for `X86`.
        fn exit_success(&self) -> !;

        /// Exit QEMU using `EXIT_FAILURE`, aka `1`.
        fn exit_failure(&self) -> !;
    }

    /// RISCV64 configuration
    pub struct RISCV64 {
        /// Address of the sifive_test mapped device.
        addr: u64,
    }

    /// Encode the exit code using EXIT_FAILURE_FLAG.
    const fn exit_code_encode(code: u32) -> u32 {
        (code << 16) | EXIT_FAILURE_FLAG
    }

    impl RISCV64 {
        /// Create an instance.
        pub const fn new(addr: u64) -> Self {
            RISCV64 { addr }
        }
    }

    impl QEMUExit for RISCV64 {
        /// Exit qemu with specified exit code.
        fn exit(&self, code: u32) -> ! {
            // If code is not a special value, we need to encode it with EXIT_FAILURE_FLAG.
            let code_new = match code {
                EXIT_SUCCESS | EXIT_FAILURE | EXIT_RESET => code,
                _ => exit_code_encode(code),
            };

            unsafe {
                asm!(
                    "sw {0}, 0({1})",
                    in(reg)code_new, in(reg)self.addr
                );

                // For the case that the QEMU exit attempt did not work, transition into an infinite
                // loop. Calling `panic!()` here is unfeasible, since there is a good chance
                // this function here is the last expression in the `panic!()` handler
                // itself. This prevents a possible infinite loop.
                loop {
                    asm!("wfi", options(nomem, nostack));
                }
            }
        }

        fn exit_success(&self) -> ! {
            self.exit(EXIT_SUCCESS);
        }

        fn exit_failure(&self) -> ! {
            self.exit(EXIT_FAILURE);
        }
    }

    const VIRT_TEST: u64 = 0x100000;

    pub const QEMU_EXIT_HANDLE: RISCV64 = RISCV64::new(VIRT_TEST);