arch: Add support for m5ops using mmapped IPRs

In order to support m5ops on virtualized CPUs, we need to either
intercept hypercall instructions or provide a memory mapped m5ops
interface. Since KVM does not normally pass the results of hypercalls
to userspace, which makes that method unfeasible. This changeset
introduces support for m5ops using memory mapped mmapped IPRs. This is
implemented by adding a class of "generic" IPRs which are handled by
architecture-independent code. Such IPRs always have bit 63 set and
are handled by handleGenericIprRead() and
handleGenericIprWrite(). Platform specific impementations of
handleIprRead and handleIprWrite should use
GenericISA::isGenericIprAccess to determine if an IPR address should
be handled by the generic code instead of the architecture-specific
code. Platforms that don't need their own IPR support can reuse
GenericISA::handleIprRead() and GenericISA::handleIprWrite().

src/arch/alpha/mmapped_ipr.hh

@@ -37,27 +37,11 @@
  * ISA-specific helper functions for memory mapped IPR accesses.
  */
 
-#include "base/types.hh"
-#include "mem/packet.hh"
-
-class ThreadContext;
+#include "arch/generic/mmapped_ipr.hh"
 
 namespace AlphaISA {
-
-inline Cycles
-handleIprRead(ThreadContext *xc, Packet *pkt)
-{
-    panic("No handleIprRead implementation in Alpha\n");
-}
-
-
-inline Cycles
-handleIprWrite(ThreadContext *xc, Packet *pkt)
-{
-    panic("No handleIprWrite implementation in Alpha\n");
-}
-
-
+    using GenericISA::handleIprRead;
+    using GenericISA::handleIprWrite;
 } // namespace AlphaISA
 
 #endif // __ARCH_ALPHA_MMAPPED_IPR_HH__

src/arch/arm/mmapped_ipr.hh

@@ -39,26 +39,14 @@
  * ISA-specific helper functions for memory mapped IPR accesses.
  */
 
-#include "base/misc.hh"
-#include "mem/packet.hh"
+#include "arch/generic/mmapped_ipr.hh"
 
 class ThreadContext;
 
 namespace ArmISA
 {
-inline Cycles
-handleIprRead(ThreadContext *xc, Packet *pkt)
-{
-    panic("No implementation for handleIprRead in ARM\n");
-}
-
-inline Cycles
-handleIprWrite(ThreadContext *xc, Packet *pkt)
-{
-    panic("No implementation for handleIprWrite in ARM\n");
-}
-
-
+    using GenericISA::handleIprRead;
+    using GenericISA::handleIprWrite;
 } // namespace ArmISA
 
 #endif

src/arch/generic/SConscript

@@ -32,3 +32,4 @@ if env['TARGET_ISA'] == 'null':
     Return()
 
 Source('decode_cache.cc')
+Source('mmapped_ipr.cc')

src/arch/generic/mmapped_ipr.cc

@@ -0,0 +1,84 @@
+/*
+ * Copyright (c) 2013 Andreas Sandberg
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Andreas Sandberg
+ */
+
+#include "arch/generic/mmapped_ipr.hh"
+#include "mem/packet.hh"
+#include "mem/packet_access.hh"
+#include "sim/pseudo_inst.hh"
+
+using namespace GenericISA;
+
+static void
+handlePseudoInst(ThreadContext *xc, Packet *pkt)
+{
+    const Addr offset(pkt->getAddr() & IPR_IN_CLASS_MASK);
+    const uint8_t func((offset >> 8) & 0xFF);
+    const uint8_t subfunc(offset & 0xFF);
+    uint64_t ret;
+
+    assert((offset >> 16) == 0);
+    ret = PseudoInst::pseudoInst(xc, func, subfunc);
+    if (pkt->isRead())
+        pkt->set(ret);
+}
+
+Cycles
+GenericISA::handleGenericIprRead(ThreadContext *xc, Packet *pkt)
+{
+    Addr va(pkt->getAddr());
+    Addr cls((va & IPR_CLASS_MASK) >> IPR_CLASS_SHIFT);
+
+    switch (cls) {
+    case IPR_CLASS_PSEUDO_INST:
+        handlePseudoInst(xc, pkt);
+        break;
+    default:
+        panic("Unhandled generic IPR read: 0x%x\n", va);
+    }
+
+    return Cycles(1);
+}
+
+Cycles
+GenericISA::handleGenericIprWrite(ThreadContext *xc, Packet *pkt)
+{
+    Addr va(pkt->getAddr());
+    Addr cls((va & IPR_CLASS_MASK) >> IPR_CLASS_SHIFT);
+
+    switch (cls) {
+    case IPR_CLASS_PSEUDO_INST:
+        handlePseudoInst(xc, pkt);
+        break;
+    default:
+        panic("Unhandled generic IPR write: 0x%x\n", va);
+    }
+
+    return Cycles(1);
+}

src/arch/generic/mmapped_ipr.hh

@@ -0,0 +1,181 @@
+/*
+ * Copyright (c) 2013 Andreas Sandberg
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Andreas Sandberg
+ */
+
+#ifndef __ARCH_GENERIC_MMAPPED_IPR_HH__
+#define __ARCH_GENERIC_MMAPPED_IPR_HH__
+
+#include "base/types.hh"
+#include "mem/packet.hh"
+
+class ThreadContext;
+
+/**
+ * @file
+ *
+ * ISA-generic helper functions for memory mapped IPR accesses.
+ */
+
+namespace GenericISA
+{
+    /** @{ */
+    /**
+     * Memory requests with the MMAPPED_IPR flag are generally mapped
+     * to registers. There is a class of these registers that are
+     * internal to gem5, for example gem5 pseudo-ops in virtualized
+     * mode.
+     *
+     * In order to make the IPR space manageable we always set bit 63
+     * (IPR_GENERIC) for accesses that should be handled by the
+     * generic ISA code. Architectures may use the rest of the IPR
+     * space internally.
+     */
+
+    /** Is this a generic IPR access? */
+    const Addr IPR_GENERIC = ULL(0x8000000000000000);
+
+    /** @{ */
+    /** Mask when extracting the class of a generic IPR */
+    const Addr IPR_CLASS_MASK = ULL(0x7FFF000000000000);
+    /** Shift amount when extracting the class of a generic IPR */
+    const int IPR_CLASS_SHIFT = 48;
+    /** @} */
+
+    /** Mask to extract the offset in within a generic IPR class */
+    const Addr IPR_IN_CLASS_MASK = ULL(0x0000FFFFFFFFFFFF);
+
+    /** gem5 pseudo-inst emulation.
+     *
+     * Read and writes to this class execute gem5
+     * pseudo-instructions. A write discards the return value of the
+     * instruction, while a read returns it.
+     *
+     * @see pseudoInst()
+     */
+    const Addr IPR_CLASS_PSEUDO_INST = 0x0;
+
+    /** @} */
+
+    /**
+     * Generate a generic IPR address that emulates a pseudo inst
+     *
+     * @see PseudoInst::pseudoInst()
+     *
+     * @param func Function ID to call.
+     * @param subfunc Sub-function, usually 0.
+     * @return Address in the IPR space corresponding to the call.
+     */
+    inline Addr
+    iprAddressPseudoInst(uint8_t func, uint8_t subfunc)
+    {
+        return IPR_GENERIC | (IPR_CLASS_PSEUDO_INST << IPR_CLASS_SHIFT)  |
+            (func << 8) | subfunc;
+    }
+
+    /**
+     * Check if this is an platform independent IPR access
+     *
+     * Accesses to internal platform independent gem5 registers are
+     * handled by handleGenericIprRead() and
+     * handleGenericIprWrite(). This method determines if a packet
+     * should be routed to those functions instead of the platform
+     * specific code.
+     *
+     * @see handleGenericIprRead
+     * @see handleGenericIprWrite
+     */
+    inline bool
+    isGenericIprAccess(const Packet *pkt)
+    {
+        return pkt->getAddr() & IPR_GENERIC;
+    }
+
+    /**
+     * Handle generic IPR reads
+     *
+     * @param xc Thread context of the current thread.
+     * @param pkt Packet from the CPU
+     * @return Latency in CPU cycles
+     */
+    Cycles handleGenericIprRead(ThreadContext *xc, Packet *pkt);
+    /**
+     * Handle generic IPR writes
+     *
+     * @param xc Thread context of the current thread.
+     * @param pkt Packet from the CPU
+     * @return Latency in CPU cycles
+     */
+    Cycles handleGenericIprWrite(ThreadContext *xc, Packet *pkt);
+
+    /**
+     * Helper function to handle IPRs when the target architecture doesn't
+     * need its own IPR handling.
+     *
+     * This function calls handleGenericIprRead if the accessing a
+     * generic IPR and panics otherwise.
+     *
+     * @param xc Thread context of the current thread.
+     * @param pkt Packet from the CPU
+     * @return Latency in CPU cycles
+     */
+    inline Cycles
+    handleIprRead(ThreadContext *xc, Packet *pkt)
+    {
+        if (!isGenericIprAccess(pkt))
+            panic("Unhandled IPR access\n");
+
+        return handleGenericIprRead(xc, pkt);
+    }
+
+
+    /**
+     * Helper function to handle IPRs when the target architecture
+     * doesn't need its own IPR handling.
+     *
+     * This function calls handleGenericIprWrite if the accessing a
+     * generic IPR and panics otherwise.
+     *
+     * @param xc Thread context of the current thread.
+     * @param pkt Packet from the CPU
+     * @return Latency in CPU cycles
+     */
+    inline Cycles
+    handleIprWrite(ThreadContext *xc, Packet *pkt)
+    {
+        if (!isGenericIprAccess(pkt))
+            panic("Unhandled IPR access\n");
+
+        return handleGenericIprWrite(xc, pkt);
+    }
+
+} // namespace GenericISA
+
+
+
+#endif

src/arch/mips/mmapped_ipr.hh

@@ -37,26 +37,14 @@
  * ISA-specific helper functions for memory mapped IPR accesses.
  */
 
-#include "base/misc.hh"
-#include "mem/packet.hh"
+#include "arch/generic/mmapped_ipr.hh"
 
 class ThreadContext;
 
 namespace MipsISA
 {
-
-inline Cycles
-handleIprRead(ThreadContext *xc, Packet *pkt)
-{
-    panic("No implementation for handleIprRead in MIPS\n");
-}
-
-inline Cycles
-handleIprWrite(ThreadContext *xc, Packet *pkt)
-{
-    panic("No implementation for handleIprWrite in MIPS\n");
-}
-
+    using GenericISA::handleIprRead;
+    using GenericISA::handleIprWrite;
 } // namespace MipsISA
 
 #endif

src/arch/power/mmapped_ipr.hh

@@ -41,26 +41,14 @@
  * ISA-specific helper functions for memory mapped IPR accesses.
  */
 
-#include "base/misc.hh"
-#include "mem/packet.hh"
+#include "arch/generic/mmapped_ipr.hh"
 
 class ThreadContext;
 
 namespace PowerISA
 {
-
-inline Cycles
-handleIprRead(ThreadContext *xc, Packet *pkt)
-{
-    panic("No implementation for handleIprRead in POWER\n");
-}
-
-inline Cycles
-handleIprWrite(ThreadContext *xc, Packet *pkt)
-{
-    panic("No implementation for handleIprWrite in POWER\n");
-}
-
+    using GenericISA::handleIprRead;
+    using GenericISA::handleIprWrite;
 } // namespace PowerISA
 
 #endif // __ARCH_POWER_MMAPPED_IPR_HH__

src/arch/sparc/mmapped_ipr.hh

@@ -37,6 +37,7 @@
  * ISA-specific helper functions for memory mapped IPR accesses.
  */
 
+#include "arch/generic/mmapped_ipr.hh"
 #include "arch/sparc/tlb.hh"
 #include "cpu/thread_context.hh"
 #include "mem/packet.hh"
@@ -47,12 +48,18 @@ namespace SparcISA
 inline Cycles
 handleIprRead(ThreadContext *xc, Packet *pkt)
 {
+    if (GenericISA::isGenericIprAccess(pkt))
+        return GenericISA::handleGenericIprRead(xc, pkt);
+    else
         return xc->getDTBPtr()->doMmuRegRead(xc, pkt);
 }
 
 inline Cycles
 handleIprWrite(ThreadContext *xc, Packet *pkt)
 {
+    if (GenericISA::isGenericIprAccess(pkt))
+        return GenericISA::handleGenericIprWrite(xc, pkt);
+    else
         return xc->getDTBPtr()->doMmuRegWrite(xc, pkt);
 }
 

src/arch/x86/mmapped_ipr.hh

@@ -46,6 +46,7 @@
  * ISA-specific helper functions for memory mapped IPR accesses.
  */
 
+#include "arch/generic/mmapped_ipr.hh"
 #include "arch/x86/regs/misc.hh"
 #include "cpu/base.hh"
 #include "cpu/thread_context.hh"
@@ -56,20 +57,29 @@ namespace X86ISA
     inline Cycles
     handleIprRead(ThreadContext *xc, Packet *pkt)
     {
+        if (GenericISA::isGenericIprAccess(pkt)) {
+            return GenericISA::handleGenericIprRead(xc, pkt);
+        } else {
             Addr offset = pkt->getAddr() & mask(3);
-        MiscRegIndex index = (MiscRegIndex)(pkt->getAddr() / sizeof(MiscReg));
+            MiscRegIndex index = (MiscRegIndex)(
+                pkt->getAddr() / sizeof(MiscReg));
             MiscReg data = htog(xc->readMiscReg(index));
             // Make sure we don't trot off the end of data.
             assert(offset + pkt->getSize() <= sizeof(MiscReg));
             pkt->setData(((uint8_t *)&data) + offset);
             return Cycles(1);
         }
+    }
 
     inline Cycles
     handleIprWrite(ThreadContext *xc, Packet *pkt)
     {
+        if (GenericISA::isGenericIprAccess(pkt)) {
+            return GenericISA::handleGenericIprWrite(xc, pkt);
+        } else {
             Addr offset = pkt->getAddr() & mask(3);
-        MiscRegIndex index = (MiscRegIndex)(pkt->getAddr() / sizeof(MiscReg));
+            MiscRegIndex index = (MiscRegIndex)(
+                pkt->getAddr() / sizeof(MiscReg));
             MiscReg data;
             data = htog(xc->readMiscRegNoEffect(index));
             // Make sure we don't trot off the end of data.
@@ -79,5 +89,6 @@ namespace X86ISA
             return Cycles(1);
         }
     }
+}
 
 #endif // __ARCH_X86_MMAPPEDIPR_HH__