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Extend libtapasco with Monitor DMA Engine
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Implement suggestion of @jahofmann in:
esa-tu-darmstadt#296 (comment)

When a new device is created a dummy implementation of the DMA Engine is
used that simply does nothing. The actual DMA Engine is initialized
later when the access mode is changed from monitor to exclusive mode.

This is necessary to prevent a monitoring application like
`tapasco-debug` to allocate all DMA Buffers of the kernel driver.
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@zyno42
zyno42 committed Sep 6, 2021
1 parent d94bdfe commit 422d915
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Showing 2 changed files with 109 additions and 36 deletions.
125 changes: 89 additions & 36 deletions runtime/libtapasco/src/device.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@

use crate::allocator::{Allocator, DriverAllocator, GenericAllocator, VfioAllocator};
use crate::debug::DebugGenerator;
use crate::dma::{DMAControl, DirectDMA, DriverDMA, VfioDMA};
use crate::dma::{DMAControl, DirectDMA, DriverDMA, MonitorDMA, VfioDMA};
use crate::dma_user_space::UserSpaceDMA;
use crate::job::Job;
use crate::pe::PEId;
Expand Down Expand Up @@ -330,20 +330,9 @@ impl Device {
if name == "pcie" {
info!("Allocating the default of 4GB at 0x0 for a PCIe platform");
let mut dma_offset = 0;
let mut dma_interrupt_read = 0;
let mut dma_interrupt_write = 1;
for comp in &s.platform {
if comp.name == "PLATFORM_COMPONENT_DMA0" {
dma_offset = comp.offset;
for v in &comp.interrupts {
if v.name == "READ" {
dma_interrupt_read = v.mapping as usize;
} else if v.name == "WRITE" {
dma_interrupt_write = v.mapping as usize;
} else {
trace!("Unknown DMA interrupt: {}.", v.name);
}
}
}
}
if dma_offset == 0 {
Expand All @@ -357,36 +346,15 @@ impl Device {
allocator: Mutex::new(Box::new(
GenericAllocator::new(0, 4 * 1024 * 1024 * 1024, 64).context(AllocatorError)?,
)),
dma: Box::new(
UserSpaceDMA::new(
&tlkm_dma_file,
dma_offset as usize,
dma_interrupt_read,
dma_interrupt_write,
&platform,
settings
.get::<usize>("dma.read_buffer_size")
.context(ConfigError)?,
settings
.get::<usize>("dma.read_buffers")
.context(ConfigError)?,
settings
.get::<usize>("dma.write_buffer_size")
.context(ConfigError)?,
settings
.get::<usize>("dma.write_buffers")
.context(ConfigError)?,
)
.context(DMAError)?,
),
dma: Box::new(MonitorDMA {}),
}));
} else if name == "zynq" || (name == "zynqmp" && !zynqmp_vfio_mode) {
info!("Using driver allocation for Zynq/ZynqMP based platform.");
allocator.push(Arc::new(OffchipMemory {
allocator: Mutex::new(Box::new(
DriverAllocator::new(&tlkm_dma_file).context(AllocatorError)?,
)),
dma: Box::new(DriverDMA::new(&tlkm_dma_file)),
dma: Box::new(MonitorDMA {}),
}));
} else if name == "zynqmp" {
info!("Using VFIO mode for ZynqMP based platform.");
Expand All @@ -397,7 +365,7 @@ impl Device {
allocator: Mutex::new(Box::new(
VfioAllocator::new(&vfio_dev).context(AllocatorError)?,
)),
dma: Box::new(VfioDMA::new(&tlkm_dma_file, &vfio_dev)),
dma: Box::new(MonitorDMA {}),
}));
} else {
return Err(Error::DeviceType { name: name });
Expand Down Expand Up @@ -510,11 +478,96 @@ impl Device {
self.access = access;

if access == tlkm_access::TlkmAccessExclusive {
trace!("Re-initializing DMAEngine for exclusive access mode.");

// Now re-initialize the DMAEngine.
// TODO: I don't know if this way of doing things is correct.
// First remove the MonitorDMA:
self.offchip_memory.clear();

// Currently falls back to PCIe and Zynq allocation using the default 4GB at 0x0.
// This will be replaced with proper dynamic initialization after the status core
// has been updated to contain the required information.
info!("Again using static memory allocation due to lack of dynamic data in the status core.");
let zynqmp_vfio_mode = true;
if self.name == "pcie" {
info!("Allocating the default of 4GB at 0x0 for a PCIe platform");
let mut dma_offset = 0;
let mut dma_interrupt_read = 0;
let mut dma_interrupt_write = 1;
for comp in &self.status.platform {
if comp.name == "PLATFORM_COMPONENT_DMA0" {
dma_offset = comp.offset;
for v in &comp.interrupts {
if v.name == "READ" {
dma_interrupt_read = v.mapping as usize;
} else if v.name == "WRITE" {
dma_interrupt_write = v.mapping as usize;
} else {
trace!("Unknown DMA interrupt: {}.", v.name);
}
}
}
}
if dma_offset == 0 {
trace!("Could not find DMA engine.");
return Err(Error::DMAEngineMissing {});
}

self.offchip_memory.push(Arc::new(OffchipMemory {
allocator: Mutex::new(Box::new(
GenericAllocator::new(0, 4 * 1024 * 1024 * 1024, 64).context(AllocatorError)?,
)),
dma: Box::new(
UserSpaceDMA::new(
&self.tlkm_device_file,
dma_offset as usize,
dma_interrupt_read,
dma_interrupt_write,
&self.platform,
self.settings
.get::<usize>("dma.read_buffer_size")
.context(ConfigError)?,
self.settings
.get::<usize>("dma.read_buffers")
.context(ConfigError)?,
self.settings
.get::<usize>("dma.write_buffer_size")
.context(ConfigError)?,
self.settings
.get::<usize>("dma.write_buffers")
.context(ConfigError)?,
)
.context(DMAError)?,
),
}));
} else if self.name == "zynq" || (self.name == "zynqmp" && !zynqmp_vfio_mode) {
info!("Using driver allocation for Zynq/ZynqMP based platform.");
self.offchip_memory.push(Arc::new(OffchipMemory {
allocator: Mutex::new(Box::new(
DriverAllocator::new(&self.tlkm_device_file).context(AllocatorError)?,
)),
dma: Box::new(DriverDMA::new(&self.tlkm_device_file)),
}));
} else if self.name == "zynqmp" {
info!("Using VFIO mode for ZynqMP based platform.");
let vfio_dev = Arc::new(init_vfio(self.settings.clone()).context(VfioInitError)?);
self.offchip_memory.push(Arc::new(OffchipMemory {
allocator: Mutex::new(Box::new(
VfioAllocator::new(&vfio_dev).context(AllocatorError)?,
)),
dma: Box::new(VfioDMA::new(&self.tlkm_device_file, &vfio_dev)),
}));
} else {
return Err(Error::DeviceType { name: self.name.clone() });
}

trace!("Access changed to exclusive, resetting all interrupts.");
self.scheduler.reset_interrupts().context(SchedulerError)?;
}

trace!("Successfully acquired access.");

Ok(())
}

Expand Down
20 changes: 20 additions & 0 deletions runtime/libtapasco/src/dma.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -278,3 +278,23 @@ impl DMAControl for DirectDMA {
Ok(())
}
}


/// Use MonitorDMA for applications that only monitor other applications like tapasco-debug
/// This implementation simply does nothing
#[derive(Debug)]
pub struct MonitorDMA;

impl DMAControl for MonitorDMA {
fn copy_to(&self, _data: &[u8], _ptr: DeviceAddress) -> Result<()> {
trace!("MonitorDMA copy_to: Doing nothing.");

Ok(())
}

fn copy_from(&self, _ptr: DeviceAddress, _data: &mut [u8]) -> Result<()> {
trace!("MonitorDMA copy_to: Doing nothing.");

Ok(())
}
}

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