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using write_volatile to guarantee that the data is written to the I/O device #303

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Dec 2, 2021
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using write_volatile to guarantee that the data is written to the I/O device #303

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184 changes: 88 additions & 96 deletions src/drivers/virtio/transport/mmio.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,10 +4,11 @@
#![allow(dead_code)]

use crate::arch::mm::PhysAddr;
use core::arch::x86_64::_mm_mfence;
use core::convert::TryInto;
use core::ptr::read_volatile;
use core::ptr::{read_volatile, write_volatile};
use core::result::Result;
use core::sync::atomic::fence;
use core::sync::atomic::Ordering;
use core::u8;

use crate::drivers::error::DriverError;
Expand Down Expand Up @@ -141,24 +142,22 @@ impl ComCfg {

/// Returns the device status field.
pub fn dev_status(&self) -> u8 {
self.com_cfg.status.try_into().unwrap()
unsafe { read_volatile(&self.com_cfg.status).try_into().unwrap() }
}

/// Resets the device status field to zero.
pub fn reset_dev(&mut self) {
self.com_cfg.status = 0;
unsafe {
_mm_mfence();
write_volatile(&mut self.com_cfg.status, 0u32);
}
}

/// Sets the device status field to FAILED.
/// A driver MUST NOT initialize and use the device any further after this.
/// A driver MAY use the device again after a proper reset of the device.
pub fn set_failed(&mut self) {
self.com_cfg.status = u32::from(device::Status::FAILED);
unsafe {
_mm_mfence();
write_volatile(&mut self.com_cfg.status, u32::from(device::Status::FAILED));
}
}

Expand All @@ -167,8 +166,10 @@ impl ComCfg {
pub fn ack_dev(&mut self) {
unsafe {
let status = read_volatile(&self.com_cfg.status);
_mm_mfence();
self.com_cfg.status = status | u32::from(device::Status::ACKNOWLEDGE);
write_volatile(
&mut self.com_cfg.status,
status | u32::from(device::Status::ACKNOWLEDGE),
);
}
}

Expand All @@ -177,8 +178,10 @@ impl ComCfg {
pub fn set_drv(&mut self) {
unsafe {
let status = read_volatile(&self.com_cfg.status);
_mm_mfence();
self.com_cfg.status = status | u32::from(device::Status::DRIVER);
write_volatile(
&mut self.com_cfg.status,
status | u32::from(device::Status::DRIVER),
);
}
}

Expand All @@ -188,8 +191,10 @@ impl ComCfg {
pub fn features_ok(&mut self) {
unsafe {
let status = read_volatile(&self.com_cfg.status);
_mm_mfence();
self.com_cfg.status = status | u32::from(device::Status::FEATURES_OK);
write_volatile(
&mut self.com_cfg.status,
status | u32::from(device::Status::FEATURES_OK),
);
}
}

Expand All @@ -202,7 +207,6 @@ impl ComCfg {
pub fn check_features(&self) -> bool {
unsafe {
let status = read_volatile(&self.com_cfg.status);
_mm_mfence();
status & u32::from(device::Status::FEATURES_OK)
== u32::from(device::Status::FEATURES_OK)
}
Expand All @@ -214,8 +218,10 @@ impl ComCfg {
pub fn drv_ok(&mut self) {
unsafe {
let status = read_volatile(&self.com_cfg.status);
_mm_mfence();
self.com_cfg.status = status | u32::from(device::Status::DRIVER_OK);
write_volatile(
&mut self.com_cfg.status,
status | u32::from(device::Status::DRIVER_OK),
);
}
}

Expand Down Expand Up @@ -314,24 +320,21 @@ impl IsrStatus {
pub fn is_interrupt(&self) -> bool {
unsafe {
let status = read_volatile(&self.raw.interrupt_status);
_mm_mfence();
status & 0x1 == 0x1
}
}

pub fn is_cfg_change(&self) -> bool {
unsafe {
let status = read_volatile(&self.raw.interrupt_status);
_mm_mfence();
status & 0x2 == 0x2
}
}

pub fn acknowledge(&mut self) {
unsafe {
let status = read_volatile(&self.raw.interrupt_status);
_mm_mfence();
self.raw.interrupt_ack = status;
write_volatile(&mut self.raw.interrupt_ack, status);
}
}
}
Expand Down Expand Up @@ -440,149 +443,130 @@ pub struct MmioRegisterLayout {

impl MmioRegisterLayout {
pub fn get_magic_value(&self) -> u32 {
self.magic_value
unsafe { read_volatile(&self.magic_value) }
}

pub fn get_version(&self) -> u32 {
self.version
unsafe { read_volatile(&self.version) }
}

pub fn get_device_id(&self) -> DevId {
self.device_id
unsafe { read_volatile(&self.device_id) }
}

pub fn enable_queue(&mut self, sel: u32) {
self.queue_sel = sel;
unsafe {
_mm_mfence();
write_volatile(&mut self.queue_sel, sel);
write_volatile(&mut self.queue_ready, 1u32);
}
self.queue_ready = 1;
}

pub fn get_max_queue_size(&mut self, sel: u32) -> u32 {
self.queue_sel = sel;
unsafe {
_mm_mfence();
write_volatile(&mut self.queue_sel, sel);
read_volatile(&self.queue_num_max)
}
self.queue_num_max
}

pub fn set_queue_size(&mut self, sel: u32, size: u32) -> u32 {
self.queue_sel = sel;
unsafe {
_mm_mfence();
}
let num_max = self.queue_num_max;
write_volatile(&mut self.queue_sel, sel);

if num_max >= size {
self.queue_num = size;
size
} else {
self.queue_num = num_max;
num_max
let num_max = read_volatile(&self.queue_num_max);

if num_max >= size {
write_volatile(&mut self.queue_num, size);
size
} else {
write_volatile(&mut self.queue_num, num_max);
num_max
}
}
}

pub fn set_ring_addr(&mut self, sel: u32, addr: PhysAddr) {
self.queue_sel = sel;
unsafe {
_mm_mfence();
write_volatile(&mut self.queue_sel, sel);
write_volatile(&mut self.queue_desc_low, addr.as_u64() as u32);
write_volatile(&mut self.queue_desc_high, (addr.as_u64() >> 32) as u32);
}
self.queue_desc_low = addr.as_u64() as u32;
self.queue_desc_high = (addr.as_u64() >> 32) as u32;
}

pub fn set_drv_ctrl_addr(&mut self, sel: u32, addr: PhysAddr) {
self.queue_sel = sel;
unsafe {
_mm_mfence();
write_volatile(&mut self.queue_sel, sel);
write_volatile(&mut self.queue_driver_low, addr.as_u64() as u32);
write_volatile(&mut self.queue_driver_high, (addr.as_u64() >> 32) as u32);
}
self.queue_driver_low = addr.as_u64() as u32;
self.queue_driver_high = (addr.as_u64() >> 32) as u32;
}

pub fn set_dev_ctrl_addr(&mut self, sel: u32, addr: PhysAddr) {
self.queue_sel = sel;
unsafe {
_mm_mfence();
write_volatile(&mut self.queue_sel, sel);
write_volatile(&mut self.queue_device_low, addr.as_u64() as u32);
write_volatile(&mut self.queue_device_high, (addr.as_u64() >> 32) as u32);
}
self.queue_device_low = addr.as_u64() as u32;
self.queue_device_high = (addr.as_u64() >> 32) as u32;
}

pub fn is_queue_ready(&mut self, sel: u32) -> bool {
self.queue_sel = sel;
unsafe {
_mm_mfence();
write_volatile(&mut self.queue_sel, sel);
read_volatile(&self.queue_ready) != 0
}
self.queue_ready != 0
}

pub fn dev_features(&mut self) -> u64 {
// Indicate device to show high 32 bits in device_feature field.
// See Virtio specification v1.1. - 4.1.4.3
self.device_features_sel = 1;
unsafe {
_mm_mfence();
}
write_volatile(&mut self.device_features_sel, 1u32);

// read high 32 bits of device features
let mut dev_feat = u64::from(self.device_features) << 32;
unsafe {
_mm_mfence();
}
// read high 32 bits of device features
let mut dev_feat = u64::from(read_volatile(&self.device_features)) << 32;

// Indicate device to show low 32 bits in device_feature field.
// See Virtio specification v1.1. - 4.1.4.3
self.device_features_sel = 0;
unsafe {
_mm_mfence();
}
// Indicate device to show low 32 bits in device_feature field.
// See Virtio specification v1.1. - 4.1.4.3
write_volatile(&mut self.device_features_sel, 0u32);

// read low 32 bits of device features
dev_feat |= u64::from(self.device_features);
// read low 32 bits of device features
dev_feat |= u64::from(read_volatile(&self.device_features));

dev_feat
dev_feat
}
}

/// Write selected features into driver_select field.
pub fn set_drv_features(&mut self, feats: u64) {
let high: u32 = (feats >> 32) as u32;
let low: u32 = feats as u32;

// Indicate to device that driver_features field shows low 32 bits.
// See Virtio specification v1.1. - 4.1.4.3
self.driver_features_sel = 0;
unsafe {
_mm_mfence();
}
// Indicate to device that driver_features field shows low 32 bits.
// See Virtio specification v1.1. - 4.1.4.3
write_volatile(&mut self.driver_features_sel, 0u32);

// write low 32 bits of device features
self.driver_features = low;
unsafe {
_mm_mfence();
}
// write low 32 bits of device features
write_volatile(&mut self.driver_features, low);

// Indicate to device that driver_features field shows high 32 bits.
// See Virtio specification v1.1. - 4.1.4.3
self.driver_features_sel = 1;
unsafe {
_mm_mfence();
}
// Indicate to device that driver_features field shows high 32 bits.
// See Virtio specification v1.1. - 4.1.4.3
write_volatile(&mut self.driver_features_sel, 1u32);

// write high 32 bits of device features
self.driver_features = high;
// write high 32 bits of device features
write_volatile(&mut self.driver_features, high);
}
}

pub fn get_config(&mut self) -> [u32; 3] {
// see Virtio specification v1.1 - 2.4.1
unsafe {
loop {
let before = read_volatile(&self.config_generation);
_mm_mfence();
fence(Ordering::SeqCst);
let config = read_volatile(&self.config);
_mm_mfence();
fence(Ordering::SeqCst);
let after = read_volatile(&self.config_generation);
fence(Ordering::SeqCst);

if before == after {
return config;
Expand All @@ -594,12 +578,20 @@ impl MmioRegisterLayout {
pub fn print_information(&mut self) {
infoheader!(" MMIO RREGISTER LAYOUT INFORMATION ");

infoentry!("Device version", "{:#X}", self.version);
infoentry!("Device ID", "{:?}", self.device_id);
infoentry!("Vendor ID", "{:#X}", self.vendor_id);
infoentry!("Device version", "{:#X}", self.get_version());
infoentry!("Device ID", "{:?}", unsafe {
read_volatile(&self.device_id)
});
infoentry!("Vendor ID", "{:#X}", unsafe {
read_volatile(&self.vendor_id)
});
infoentry!("Device Features", "{:#X}", self.dev_features());
infoentry!("Interrupt status", "{:#X}", self.interrupt_status);
infoentry!("Device status", "{:#X}", self.status);
infoentry!("Interrupt status", "{:#X}", unsafe {
read_volatile(&self.interrupt_status)
});
infoentry!("Device status", "{:#X}", unsafe {
read_volatile(&self.status)
});
infoentry!("Configuration space", "{:#X?}", self.get_config());

infofooter!();
Expand Down