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dev, kvm: Add a fast KVM-aware mode in DmaReadFifo

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Use a fast, functional, read operations keep the DMA FIFO full when
running in KVM mode.

Change-Id: I5b378c2fb6a1d3e687cef15e807e63a0a53a60e2
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/2226
Reviewed-by: Rahul Thakur <rjthakur@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
This commit is contained in:
Sudhanshu Jha 2017-02-27 10:29:56 +00:00 committed by Andreas Sandberg
parent 746e2f3c27
commit 82a8230aa7
2 changed files with 44 additions and 10 deletions
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44
src/dev/dma_device.cc
View file

@ -1,5 +1,5 @@
/*
* Copyright (c) 2012, 2015 ARM Limited
* Copyright (c) 2012, 2015, 2017 ARM Limited
* All rights reserved.
*
* The license below extends only to copyright in the software and shall
@ -50,6 +50,7 @@
#include "base/chunk_generator.hh"
#include "debug/DMA.hh"
#include "debug/Drain.hh"
#include "mem/port_proxy.hh"
#include "sim/system.hh"
DmaPort::DmaPort(MemObject *dev, System *s)
@ -371,6 +372,40 @@ DmaReadFifo::resumeFill()
return;
const bool old_eob(atEndOfBlock());
if (port.sys->bypassCaches())
resumeFillFunctional();
else
resumeFillTiming();
if (!old_eob && atEndOfBlock())
onEndOfBlock();
}
void
DmaReadFifo::resumeFillFunctional()
{
const size_t fifo_space = buffer.capacity() - buffer.size();
const size_t kvm_watermark = port.sys->cacheLineSize();
if (fifo_space >= kvm_watermark || buffer.capacity() < kvm_watermark) {
const size_t block_remaining = endAddr - nextAddr;
const size_t xfer_size = std::min(fifo_space, block_remaining);
std::vector<uint8_t> tmp_buffer(xfer_size);
assert(pendingRequests.empty());
DPRINTF(DMA, "KVM Bypassing startAddr=%#x xfer_size=%#x " \
"fifo_space=%#x block_remaining=%#x\n",
nextAddr, xfer_size, fifo_space, block_remaining);
port.sys->physProxy.readBlob(nextAddr, tmp_buffer.data(), xfer_size);
buffer.write(tmp_buffer.begin(), xfer_size);
nextAddr += xfer_size;
}
}
void
DmaReadFifo::resumeFillTiming()
{
size_t size_pending(0);
for (auto &e : pendingRequests)
size_pending += e->requestSize();
@ -392,11 +427,6 @@ DmaReadFifo::resumeFill()
pendingRequests.emplace_back(std::move(event));
}
// EOB can be set before a call to dmaDone() if in-flight accesses
// have been canceled.
if (!old_eob && atEndOfBlock())
onEndOfBlock();
}
void
@ -430,8 +460,6 @@ DmaReadFifo::handlePending()
signalDrainDone();
}
DrainState
DmaReadFifo::drain()
{

10
src/dev/dma_device.hh
View file

@ -1,5 +1,5 @@
/*
* Copyright (c) 2012-2013, 2015 ARM Limited
* Copyright (c) 2012-2013, 2015, 2017 ARM Limited
* All rights reserved.
*
* The license below extends only to copyright in the software and shall
@ -494,9 +494,15 @@ class DmaReadFifo : public Drainable, public Serializable
/** Handle pending requests that have been flagged as done. */
void handlePending();
/** Try to issue new DMA requests */
/** Try to issue new DMA requests or bypass DMA requests*/
void resumeFill();
/** Try to issue new DMA requests during normal execution*/
void resumeFillTiming();
/** Try to bypass DMA requests in KVM execution mode */
void resumeFillFunctional();
private: // Internal state
Fifo<uint8_t> buffer;