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Finished setup, rearranged queue creation and testing bits. This makes it so we don't have to free anything if we fail after setting up the queue.

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This commit is contained in:
Stephen Marz 2020-03-12 13:36:08 -04:00
parent a32c6fc995
commit f5ce75dbe8
1 changed files with 48 additions and 16 deletions
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62
risc_v/ch9/src/block.rs
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@ -54,8 +54,6 @@ pub struct BlockDevice {
idx: u16,
}
static mut BLOCK_DEVICE_ARRAY: Option<VecDeque<BlockDevice>> = None;
// Feature bits
pub const VIRTIO_BLK_F_SIZE_MAX: u32 = 1;
pub const VIRTIO_BLK_F_SEG_MAX: u32 = 2;
@ -68,15 +66,23 @@ pub const VIRTIO_BLK_F_CONFIG_WCE: u32 = 11;
pub const VIRTIO_BLK_F_DISCARD: u32 = 13;
pub const VIRTIO_BLK_F_WRITE_ZEROES: u32 = 14;
pub fn init_block_system() {
// Much like with processes, Rust requires some initialization
// when we declare a static. In this case, we use the Option
// value type to signal that the variable exists, but not the
// queue itself. We will replace this with an actual queue when
// we initialize the block system.
static mut BLOCK_DEVICES: Option<VecDeque<BlockDevice>> = None;
pub fn init() {
unsafe {
BLOCK_DEVICE_ARRAY.replace(VecDeque::with_capacity(1));
BLOCK_DEVICES.replace(VecDeque::with_capacity(1));
}
}
pub fn setup_block_device(ptr: *mut u32) -> bool {
unsafe {
if let Some(mut vdq) = BLOCK_DEVICE_ARRAY.take() {
if let Some(mut vdq) = BLOCK_DEVICES.take() {
// [Driver] Device Initialization
// 1. Reset the device (write 0 into status)
ptr.add(MmioOffsets::Status.scale32()).write_volatile(0);
@ -104,30 +110,56 @@ pub fn setup_block_device(ptr: *mut u32) -> bool {
return false;
}
// 7. Perform device-specific setup.
// Set the queue num. We have to make sure that the queue size is valid
// because the device can only take a certain size.
let qnmax = ptr.add(MmioOffsets::QueueNumMax.scale32()).read_volatile();
ptr.add(MmioOffsets::QueueNum.scale32()).write_volatile(VIRTIO_RING_SIZE as u32);
if VIRTIO_RING_SIZE as u32 > qnmax {
print!("queue size fail...");
return false;
}
// First, if the block device array is empty, create it!
// We add 4096 to round this up and then do an integer divide
// to truncate the decimal.
// We add 4095 to round this up and then do an integer divide
// to truncate the decimal. We don't add 4096, because if it is
// exactly 4096 bytes, we would get two pages, not one.
let num_pages =
(size_of::<Queue>() + PAGE_SIZE) / PAGE_SIZE;
(size_of::<Queue>() + PAGE_SIZE - 1) / PAGE_SIZE;
// println!("np = {}", num_pages);
// We allocate a page for each device. This will the the descriptor
// where we can communicate with the block device. We will still use
// an MMIO register (in particular, QueueNotify) to actually tell
// the device we put something in memory.
// We also have to be careful with memory ordering. We don't want to
// issue a notify before all memory writes have finished. We will
// look at that later, but we need what is called a memory "fence"
// or barrier.
let queue_ptr = zalloc(num_pages) as *mut Queue;
let queue_pfn = queue_ptr as u32;
// QueuePFN is a physical page number, however it appears for QEMU
// we have to write the entire memory address. This is a physical
// memory address where we (the OS) and the block device have
// in common for making and receiving requests.
ptr.add(MmioOffsets::QueuePfn.scale32())
.write_volatile(queue_pfn);
// We need to store all of this data as a "BlockDevice" structure
// We will be referring to this structure when making block requests
// AND when handling responses.
let bd = BlockDevice { queue: queue_ptr,
dev: ptr,
idx: 1, };
vdq.push_back(bd);
ptr.add(MmioOffsets::QueuePfn.scale32())
.write_volatile(queue_pfn);
BLOCK_DEVICE_ARRAY.replace(vdq);
ptr.add(MmioOffsets::QueueNum.scale32()).write_volatile(VIRTIO_RING_SIZE as u32);
let qn = ptr.add(MmioOffsets::QueueNum.scale32()).read_volatile();
let qnmax = ptr.add(MmioOffsets::QueueNumMax.scale32()).read_volatile();
// Update the global block device array.
BLOCK_DEVICES.replace(vdq);
// 8. Set the DRIVER_OK status bit. Device is now "live"
status_bits |= StatusField::DriverOk.val32();
ptr.add(MmioOffsets::Status.scale32()).write_volatile(status_bits);
true
}
} /* if let Some(mut vdq) = BLOCK_DEVICES.take() */
else {
// If we get here, the block devices array couldn't be taken. This can
// be due to duplicate access or that init wasn't called before this setup.
false
}
}