gopkg.in/ubuntu-core/snappy.v0@v0.0.0-20210902073436-25a8614f10a6/interfaces/builtin/kvm.go (about)

     1  // -*- Mode: Go; indent-tabs-mode: t -*-
     2  
     3  /*
     4   * Copyright (C) 2017-2019 Canonical Ltd
     5   *
     6   * This program is free software: you can redistribute it and/or modify
     7   * it under the terms of the GNU General Public License version 3 as
     8   * published by the Free Software Foundation.
     9   *
    10   * This program is distributed in the hope that it will be useful,
    11   * but WITHOUT ANY WARRANTY; without even the implied warranty of
    12   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    13   * GNU General Public License for more details.
    14   *
    15   * You should have received a copy of the GNU General Public License
    16   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
    17   *
    18   */
    19  
    20  package builtin
    21  
    22  import (
    23  	"fmt"
    24  	"io/ioutil"
    25  	"regexp"
    26  	"strings"
    27  
    28  	"github.com/snapcore/snapd/interfaces"
    29  	"github.com/snapcore/snapd/interfaces/kmod"
    30  	"github.com/snapcore/snapd/logger"
    31  	"github.com/snapcore/snapd/strutil"
    32  )
    33  
    34  const kvmSummary = `allows access to the kvm device`
    35  
    36  const kvmBaseDeclarationSlots = `
    37    kvm:
    38      allow-installation:
    39        slot-snap-type:
    40          - core
    41      deny-auto-connection: true
    42  `
    43  
    44  const kvmConnectedPlugAppArmor = `
    45  # Description: Allow write access to kvm.
    46  # See 'man kvm' for details.
    47  
    48  /dev/kvm rw,
    49  
    50  # Allow nested virtualization checks for different CPU models and architectures (where it is supported).
    51  /sys/module/kvm_intel/parameters/nested r,
    52  /sys/module/kvm_amd/parameters/nested r,
    53  /sys/module/kvm_hv/parameters/nested r, # PPC64.
    54  /sys/module/kvm/parameters/nested r, # S390.
    55  `
    56  
    57  var kvmConnectedPlugUDev = []string{`KERNEL=="kvm"`}
    58  
    59  type kvmInterface struct {
    60  	commonInterface
    61  }
    62  
    63  var procCpuinfo = "/proc/cpuinfo"
    64  var flagsMatcher = regexp.MustCompile(`(?m)^flags\s+:\s+(.*)$`).FindSubmatch
    65  
    66  func getCpuFlags() (flags []string, err error) {
    67  	buf, err := ioutil.ReadFile(procCpuinfo)
    68  	if err != nil {
    69  		// if we can't read cpuinfo, we want to know _why_
    70  		return nil, fmt.Errorf("unable to read %v: %v", procCpuinfo, err)
    71  	}
    72  
    73  	// want to capture the text after 'flags:' entry
    74  	match := flagsMatcher(buf)
    75  	if len(match) == 0 {
    76  		return nil, fmt.Errorf("%v does not contain a 'flags:' entry", procCpuinfo)
    77  	}
    78  
    79  	// match[0] has whole matching line, match[1] must exist as it has the captured text after 'flags:'
    80  	cpu_flags := strings.Fields(string(match[1]))
    81  	return cpu_flags, nil
    82  }
    83  
    84  func (iface *kvmInterface) KModConnectedPlug(spec *kmod.Specification, plug *interfaces.ConnectedPlug, slot *interfaces.ConnectedSlot) error {
    85  	// Check CPU capabilities to load suitable module
    86  	// NOTE: this only considers i386, x86_64 and amd64 CPUs, but some ARM, PPC and S390 CPUs also support KVM
    87  	m := "kvm"
    88  	cpu_flags, err := getCpuFlags()
    89  	if err != nil {
    90  		logger.Debugf("kvm: fetching cpu info failed: %v", err)
    91  	}
    92  
    93  	if strutil.ListContains(cpu_flags, "vmx") {
    94  		m = "kvm_intel"
    95  	} else if strutil.ListContains(cpu_flags, "svm") {
    96  		m = "kvm_amd"
    97  	} else {
    98  		// CPU appears not to support KVM extensions, fall back to bare kvm module as it appears
    99  		// sufficient for some architectures
   100  		logger.Noticef("kvm: failed to detect CPU specific KVM support, will attempt to modprobe generic KVM support")
   101  	}
   102  
   103  	if err := spec.AddModule(m); err != nil {
   104  		return nil
   105  	}
   106  	return nil
   107  }
   108  
   109  func init() {
   110  	registerIface(&kvmInterface{commonInterface{
   111  		name:                  "kvm",
   112  		summary:               kvmSummary,
   113  		implicitOnCore:        true,
   114  		implicitOnClassic:     true,
   115  		baseDeclarationSlots:  kvmBaseDeclarationSlots,
   116  		connectedPlugAppArmor: kvmConnectedPlugAppArmor,
   117  		connectedPlugUDev:     kvmConnectedPlugUDev,
   118  	}})
   119  }