kvm: Initial x86 support

This changeset adds support for KVM on x86. Full support is split
across a number of commits since some features are relatively
complex. This changeset includes support for:

 * Integer state synchronization (including segment regs)
 * CPUID (gem5's CPUID values are inserted into KVM)
 * x86 legacy IO (remapped and handled by gem5's memory system)
 * Memory mapped IO
 * PCI
 * MSRs
 * State dumping

Most of the functionality is fairly straight forward. There are some
quirks to support PCI enumerations since this is done in the TLB(!) in
the simulated CPUs. We currently replicate some of that code.

Unlike the ARM implementation, the x86 implementation of the virtual
CPU does not use the cycles hardware counter. KVM on x86 simulates the
time stamp counter (TSC) in the kernel. If we just measure host cycles
using perfevent, we might end up measuring a slightly different number
of cycles. If we don't get the cycle accounting right, we might end up
rewinding the TSC, with all kinds of chaos as a result.

An additional feature of the KVM CPU on x86 is extended state
dumping. This enables Python scripts controlling the simulator to
request dumping of a subset of the processor state. The following
methods are currenlty supported:

 * dumpFpuRegs
 * dumpIntRegs
 * dumpSpecRegs
 * dumpDebugRegs
 * dumpXCRs
 * dumpXSave
 * dumpVCpuEvents
 * dumpMSRs

Known limitations:
  * M5 ops are currently not supported.
  * FPU synchronization is not supported (only affects CPU switching).

Both of the limitations will be addressed in separate commits.

SConstruct

@@ -942,6 +942,7 @@ if not have_kvm:
 def is_isa_kvm_compatible(isa):
     isa_comp_table = {
         "arm" : ( "armv7l" ),
+        "x86" : ( "x86_64" ),
         }
     try:
         import platform

src/cpu/kvm/SConscript

@@ -51,6 +51,9 @@ if env['USE_KVM']:
     if env['TARGET_ISA'] == 'arm':
         SimObject('ArmKvmCPU.py')
         Source('arm_cpu.cc')
+    elif env['TARGET_ISA'] == 'x86':
+        SimObject('X86KvmCPU.py')
+        Source('x86_cpu.cc')
 
     DebugFlag('Kvm', 'Basic KVM Functionality')
     DebugFlag('KvmContext', 'KVM/gem5 context synchronization')

src/cpu/kvm/X86KvmCPU.py

@@ -0,0 +1,45 @@
+# 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
+
+from m5.params import *
+from BaseKvmCPU import BaseKvmCPU
+
+class X86KvmCPU(BaseKvmCPU):
+    type = 'X86KvmCPU'
+    cxx_header = "cpu/kvm/x86_cpu.hh"
+
+    @classmethod
+    def export_methods(cls, code):
+        code('''
+      void dumpFpuRegs();
+      void dumpIntRegs();
+      void dumpSpecRegs();
+      void dumpXCRs();
+      void dumpXSave();
+      void dumpVCpuEvents();
+''')

src/cpu/kvm/vm.cc

@@ -45,6 +45,7 @@
 #include <unistd.h>
 
 #include <cerrno>
+#include <memory>
 
 #include "cpu/kvm/vm.hh"
 #include "debug/Kvm.hh"
@@ -139,6 +140,46 @@ Kvm::capIRQChip() const
     return checkExtension(KVM_CAP_IRQCHIP) != 0;
 }
 
+bool
+Kvm::capVCPUEvents() const
+{
+#ifdef KVM_CAP_VCPU_EVENTS
+    return checkExtension(KVM_CAP_VCPU_EVENTS) != 0;
+#else
+    return false;
+#endif
+}
+
+bool
+Kvm::capDebugRegs() const
+{
+#ifdef KVM_CAP_DEBUGREGS
+    return checkExtension(KVM_CAP_DEBUGREGS) != 0;
+#else
+    return false;
+#endif
+}
+
+bool
+Kvm::capXCRs() const
+{
+#ifdef KVM_CAP_XCRS
+    return checkExtension(KVM_CAP_XCRS) != 0;
+#else
+    return false;
+#endif
+}
+
+bool
+Kvm::capXSave() const
+{
+#ifdef KVM_CAP_XSAVE
+    return checkExtension(KVM_CAP_XSAVE) != 0;
+#else
+    return false;
+#endif
+}
+
 bool
 Kvm::getSupportedCPUID(struct kvm_cpuid2 &cpuid) const
 {
@@ -155,6 +196,61 @@ Kvm::getSupportedCPUID(struct kvm_cpuid2 &cpuid) const
 #endif
 }
 
+const Kvm::CPUIDVector &
+Kvm::getSupportedCPUID() const
+{
+    if (supportedCPUIDCache.empty()) {
+        std::unique_ptr<struct kvm_cpuid2> cpuid;
+        int i(1);
+        do {
+            cpuid.reset((struct kvm_cpuid2 *)operator new(
+                            sizeof(kvm_cpuid2) + i * sizeof(kvm_cpuid_entry2)));
+
+            cpuid->nent = i;
+            ++i;
+        } while (!getSupportedCPUID(*cpuid));
+        supportedCPUIDCache.assign(cpuid->entries,
+                                   cpuid->entries + cpuid->nent);
+    }
+
+    return supportedCPUIDCache;
+}
+
+bool
+Kvm::getSupportedMSRs(struct kvm_msr_list &msrs) const
+{
+#if defined(__i386__) || defined(__x86_64__)
+    if (ioctl(KVM_GET_MSR_INDEX_LIST, (void *)&msrs) == -1) {
+        if (errno == E2BIG)
+            return false;
+        else
+            panic("KVM: Failed to get supported CPUID (errno: %i)\n", errno);
+    } else
+        return true;
+#else
+    panic("KVM: getSupportedCPUID is unsupported on this platform.\n");
+#endif
+}
+
+const Kvm::MSRIndexVector &
+Kvm::getSupportedMSRs() const
+{
+    if (supportedMSRCache.empty()) {
+        std::unique_ptr<struct kvm_msr_list> msrs;
+        int i(0);
+        do {
+            msrs.reset((struct kvm_msr_list *)operator new(
+                           sizeof(kvm_msr_list) + i * sizeof(uint32_t)));
+
+            msrs->nmsrs = i;
+            ++i;
+        } while (!getSupportedMSRs(*msrs));
+        supportedMSRCache.assign(msrs->indices, msrs->indices + msrs->nmsrs);
+    }
+
+    return supportedMSRCache;
+}
+
 int
 Kvm::checkExtension(int extension) const
 {

src/cpu/kvm/vm.hh

@@ -40,6 +40,8 @@
 #ifndef __CPU_KVM_KVMVM_HH__
 #define __CPU_KVM_KVMVM_HH__
 
+#include <vector>
+
 #include "base/addr_range.hh"
 #include "sim/sim_object.hh"
 
@@ -72,6 +74,9 @@ class Kvm
     friend class KvmVM;
 
   public:
+    typedef std::vector<struct kvm_cpuid_entry2> CPUIDVector;
+    typedef std::vector<uint32_t> MSRIndexVector;
+
     virtual ~Kvm();
 
     Kvm *create();
@@ -117,6 +122,18 @@ class Kvm
      * @see KvmVM::createIRQChip()
      */
     bool capIRQChip() const;
+
+    /** Support for getting and setting the kvm_vcpu_events structure. */
+    bool capVCPUEvents() const;
+
+    /** Support for getting and setting the kvm_debugregs structure. */
+    bool capDebugRegs() const;
+
+    /** Support for getting and setting the x86 XCRs. */
+    bool capXCRs() const;
+
+    /** Support for getting and setting the kvm_xsave structure. */
+    bool capXSave() const;
     /** @} */
 
     /**
@@ -128,6 +145,35 @@ class Kvm
      */
     bool getSupportedCPUID(struct kvm_cpuid2 &cpuid) const;
 
+    /**
+     * Get the CPUID features supported by the hardware and Kvm.
+     *
+     * @note Requires capExtendedCPUID().
+     *
+     * @note This method uses an internal cache to minimize the number
+     * of calls into the kernel.
+     *
+     * @return Reference to cached MSR index list.
+     */
+    const CPUIDVector &getSupportedCPUID() const;
+
+    /**
+     * Get the MSRs supported by the hardware and Kvm.
+     *
+     * @return False if the allocation is too small, true on success.
+     */
+    bool getSupportedMSRs(struct kvm_msr_list &msrs) const;
+
+    /**
+     * Get the MSRs supported by the hardware and Kvm.
+     *
+     * @note This method uses an internal cache to minimize the number
+     * of calls into the kernel.
+     *
+     * @return Reference to cached MSR index list.
+     */
+    const MSRIndexVector &getSupportedMSRs() const;
+
   protected:
     /**
      * Check for the presence of an extension to the KVM API.
@@ -186,6 +232,12 @@ class Kvm
     /** Size of the MMAPed vCPU parameter area. */
     int vcpuMMapSize;
 
+    /** Cached vector of supported CPUID entries. */
+    mutable CPUIDVector supportedCPUIDCache;
+
+    /** Cached vector of supported MSRs. */
+    mutable MSRIndexVector supportedMSRCache;
+
     /** Singleton instance */
     static Kvm *instance;
 };

src/cpu/kvm/x86_cpu.hh

@@ -0,0 +1,225 @@
+/*
+ * 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 __CPU_KVM_X86_CPU_HH__
+#define __CPU_KVM_X86_CPU_HH__
+
+#include "cpu/kvm/base.hh"
+#include "cpu/kvm/vm.hh"
+#include "params/X86KvmCPU.hh"
+
+/**
+ * x86 implementation of a KVM-based hardware virtualized CPU.
+ */
+class X86KvmCPU : public BaseKvmCPU
+{
+  public:
+    X86KvmCPU(X86KvmCPUParams *params);
+    virtual ~X86KvmCPU();
+
+    void startup();
+
+    /** @{ */
+    void dump();
+    void dumpFpuRegs() const;
+    void dumpIntRegs() const;
+    void dumpSpecRegs() const;
+    void dumpDebugRegs() const;
+    void dumpXCRs() const;
+    void dumpXSave() const;
+    void dumpVCpuEvents() const;
+    void dumpMSRs() const;
+    /** @} */
+
+  protected:
+    typedef std::vector<struct kvm_msr_entry> KvmMSRVector;
+
+    Tick kvmRun(Tick ticks);
+
+    /**
+     * Run the virtual CPU until draining completes.
+     *
+     * In addition to the base functionality provided by
+     * BaseKvmCPU::kvmRunDrain(), this method handles x86-specific
+     * cases where there are pending interrupt events in the virtual
+     * CPU.  These are handled by requesting an interrupt window if
+     * interrupts are pending (causing the vCPU to execute until
+     * interrupts can be delivered again).
+     *
+     * @see BaseKvmCPU::kvmRunDrain()
+     * @see archIsDrained()
+     *
+     * @return Number of ticks executed
+     */
+    Tick kvmRunDrain();
+
+    /** Wrapper that synchronizes state in kvm_run */
+    Tick kvmRunWrapper(Tick ticks);
+
+    uint64_t getHostCycles() const;
+
+    /**
+     * Methods to access CPUID information using the extended
+     * API. Only available if Kvm::capExtendedCPUID() is true.
+     *
+     * @{
+     */
+    void setCPUID(const struct kvm_cpuid2 &cpuid);
+    void setCPUID(const Kvm::CPUIDVector &cpuid);
+    /** @} */
+
+    /**
+     * Methods to access MSRs in the guest.
+     *
+     * @{
+     */
+    void setMSRs(const struct kvm_msrs &msrs);
+    void setMSRs(const KvmMSRVector &msrs);
+    void getMSRs(struct kvm_msrs &msrs) const;
+    void setMSR(uint32_t index, uint64_t value);
+    uint64_t getMSR(uint32_t index) const;
+    /** @} */
+
+    /**
+     * Get a list of MSRs supported by both gem5 and KVM.
+     *
+     * @note This method uses an internal cache and only generates the
+     * MSR list once.
+     *
+     * @return reference to a list of msr indices
+     */
+    const Kvm::MSRIndexVector &getMsrIntersection() const;
+
+    /**
+     * Wrappers around KVM's state transfer methods.
+     *
+     * @{
+     */
+    void getDebugRegisters(struct kvm_debugregs &regs) const;
+    void setDebugRegisters(const struct kvm_debugregs &regs);
+    void getXCRs(struct kvm_xcrs &regs) const;
+    void setXCRs(const struct kvm_xcrs &regs);
+    void getXSave(struct kvm_xsave &xsave) const;
+    void setXSave(const struct kvm_xsave &xsave);
+    void getVCpuEvents(struct kvm_vcpu_events &events) const;
+    void setVCpuEvents(const struct kvm_vcpu_events &events);
+    /** @} */
+
+    void updateKvmState();
+    void updateThreadContext();
+
+    /**
+     * Inject pending interrupts from gem5 into the virtual CPU.
+     */
+    void deliverInterrupts();
+
+    /**
+     * Handle x86 legacy IO (in/out)
+     */
+    Tick handleKvmExitIO();
+
+    Tick handleKvmExitIRQWindowOpen();
+
+    /**
+     * Check if there are pending events in the vCPU that prevents it
+     * from being drained.
+     *
+     * There are cases after interrupt injection where the interrupt
+     * is still pending in the guest. This method detects such cases
+     * and requests additional draining.
+     *
+     * @return False if there are pending events in the guest, True
+     * otherwise.
+     */
+    bool archIsDrained() const;
+
+  private:
+    /**
+     * Support routines to update the state of the KVM CPU from gem5's
+     * state representation.
+     *
+     * @{
+     */
+    /** Update integer registers */
+    void updateKvmStateRegs();
+    /** Update control registers (CRx, segments, etc.) */
+    void updateKvmStateSRegs();
+    /** Update FPU and SIMD registers */
+    void updateKvmStateFPU();
+    /** Update MSR registers */
+    void updateKvmStateMSRs();
+    /** @} */
+
+    /**
+     * Support routines to update the state of gem5's thread context from
+     * KVM's state representation.
+     *
+     * @{
+     */
+    /** Update integer registers */
+    void updateThreadContextRegs();
+    /** Update control registers (CRx, segments, etc.) */
+    void updateThreadContextSRegs();
+    /** Update FPU and SIMD registers */
+    void updateThreadContextFPU();
+    /** Update MSR registers */
+    void updateThreadContextMSRs();
+    /** @} */
+
+    /** Transfer gem5's CPUID values into the virtual CPU. */
+    void updateCPUID();
+
+    /**
+     * Handle a 32-bit IO access that should be mapped to a MiscReg.
+     *
+     * @note This method can only be called on when handling IO after
+     * a KVM_EXIT_IO.
+     *
+     * @param miscreg Register to map the current IO access to.
+     */
+    void handleIOMiscReg32(int miscreg);
+
+    /** Reusable IO request */
+    Request io_req;
+
+    /** Cached intersection of supported MSRs */
+    mutable Kvm::MSRIndexVector cachedMsrIntersection;
+
+    /** @{ */
+    /** Kvm::capDebugRegs() available? */
+    bool haveDebugRegs;
+    /** Kvm::capXSave() available? */
+    bool haveXSave;
+    /** Kvm::capXCRs() available? */
+    bool haveXCRs;
+    /** @} */
+};
+
+#endif